1
|
Linsenmeier RA, Dmitriev AV. Increased Retinal Metabolism Induced by Flicker in the Isolated Mouse Retina. eNeuro 2024; 11:ENEURO.0509-23.2024. [PMID: 38641415 PMCID: PMC11089847 DOI: 10.1523/eneuro.0509-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 04/10/2024] [Accepted: 04/12/2024] [Indexed: 04/21/2024] Open
Abstract
Both the retina and brain exhibit neurovascular coupling, increased blood flow during increased neural activity. In the retina increased blood flow can be evoked by flickering light, but the magnitude of the metabolic change that underlies this is not known. Local changes in oxygen consumption (QO2) are difficult to measure in vivo when both supply and demand are changing. Here we isolated the C57BL/6J mouse retina and supplied it with oxygen from both sides of the tissue. Microelectrode recordings of PO2 were made in darkness and during 20 s of high scotopic flickering light at 1 Hz. Flicker led to a PO2 increase in the outer retina and a decrease in the inner retina, indicating that outer retinal QO2 (QOR) decreased and inner retinal QO2 (QIR) increased. A four-layer oxygen diffusion model was fitted to PO2 values obtained in darkness and at the end of flicker to determine the values of QOR and QIR. QOR in flicker was 76 ± 14% (mean and SD, n = 10) of QOR in darkness. The increase in QIR was smaller, 6.4 ± 5.0%. These metabolic changes are likely smaller than the maximum changes, because with no regeneration of pigment in the isolated retina, we limited the illumination. Further modeling indicated that at high illumination, QIR could increase by up to 45%, which is comparable to the magnitude of flow changes. This suggests that the blood flow increase is at least roughly matched to the increased metabolic demands of activity in the retina.
Collapse
Affiliation(s)
- Robert A Linsenmeier
- Departments of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208
- Neurobiology, Northwestern University, Evanston, Illinois 60208
- Department of Ophthalmology, Northwestern University, Chicago, Illinois 60611
| | - Andrey V Dmitriev
- Departments of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208
| |
Collapse
|
2
|
Dmitriev AV, Dmitriev AA, Linsenmeier RA. Diabetes-Induced Changes of the Rat ERG in Relation to Hyperglycemia and Acidosis. Curr Eye Res 2024; 49:53-61. [PMID: 37756520 PMCID: PMC10872866 DOI: 10.1080/02713683.2023.2264544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Accepted: 09/22/2023] [Indexed: 09/29/2023]
Abstract
PURPOSE To understand the mechanism of changes in the c-wave of the electroretinogram (ERG) in diabetic rats, and to explore how glucose manipulations affect the c-wave. METHODS Vitreal ERGs were recorded in control and diabetic Long-Evans rats, 3-60 weeks after IP vehicle or streptozotocin. A few experiments were performed on Brown Norway rats. Voltage responses to current pulses were used to measure the transepithelial resistance of the retinal pigment epithelium (RPE). RESULTS During development of diabetes the b-wave amplitude progressively decreased to about half of the initial amplitude after a year. In contrast, the c-wave was strongly affected from the very beginning (3 weeks) of diabetes. In control rats, the c-wave was cornea-positive at lower illuminations but was cornea-negative at higher (photopic) illumination. In diabetics, the whole amplitude-intensity curve was shifted toward negativity. The magnitude of this shift was markedly affected by acute glucose manipulations in diabetics but not in controls. Increased blood glucose made the c-wave more negative, and decreased blood glucose with insulin had the opposite effect. Experimentally induced acidification of the retina had a small effect that was different from diabetes, shifting the c-wave toward positivity, slightly in controls and more noticeably in diabetics. One reason for the significant negativity of the diabetic ERG was a decrease of the cornea-positive response of the RPE due to a decrease of the transepithelial resistance. CONCLUSIONS The ERG c-wave is more negative in diabetics than in control animals, and is far more sensitive to changes in blood glucose. The increased negativity is largely if not entirely due to changes in the transepithelial resistance of the RPE, an electrical analog of the breakdown of the blood-retinal barrier observed in other studies. The sensitivity of the c-wave to glucose in diabetics may also be due to changes in transepithelial resistance.
Collapse
Affiliation(s)
| | | | - Robert A Linsenmeier
- Department of Biomedical Engineering, Evanston and Chicago, IL
- Department of Neurobiology, Evanston and Chicago, IL
- Department of Ophthalmology Northwestern University, Evanston and Chicago, IL
| |
Collapse
|
3
|
Linsenmeier RA, Dmitriev AV, Dmitriev AA. Oxygen profiles and oxygen consumption in the isolated mouse retina. Exp Eye Res 2023; 233:109554. [PMID: 37437835 PMCID: PMC10528762 DOI: 10.1016/j.exer.2023.109554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 06/14/2023] [Accepted: 06/23/2023] [Indexed: 07/14/2023]
Abstract
The retina has a large demand for oxygen, but there is only limited information on differences between oxygen utilization (QO2) in the inner and outer retina, and limited data on mouse, which has become a prevalent animal model. This study utilized the isolated mouse retina, which allowed more detailed spatial analysis of QO2 than other methods. Oxygen sensitive microelectrodes were used to obtain profiles of oxygen tension across the isolated mouse retina, and mathematical models of retinal oxygen diffusion with four and five layers were fitted to the data to obtain values for QO2 of the outer retina (QOR) and inner retina (QIR). The boundaries between layers were free parameters in these models. The five-layer model resulted in lower error between the model and data, and agreed better with known anatomy. The three layers for the outer retina occupied half of the retina, as in prior work on rat, cat, and monkey, and the inner half of the retina could be divided into two layers, in which the one closer to the vitreous (layer 5) had much lower QO2 than the more distal inner retina (layer 4). QIR in darkness was 3.9 ml O2-100 g-1-min-1, similar to the value for intact cat retina, and did not change during light. QOR in darkness was 2.4 ml O2-100 g-1-min-1, lower than previous values in cat and rat, possibly because of damage to photoreceptors during isolation. There was a tendency for QOR to be lower in light, but it was not significant in this preparation.
Collapse
Affiliation(s)
- Robert A Linsenmeier
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, USA; Department of Neurobiology, Northwestern University, Evanston, Illinois, USA; Department of Ophthalmology, Northwestern University, Chicago, Illinois, USA.
| | - Andrey V Dmitriev
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, USA.
| | - Alexander A Dmitriev
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, USA.
| |
Collapse
|
4
|
Molins B, Mesquida M, Adan A. Bioengineering approaches for modelling retinal pathologies of the outer blood-retinal barrier. Prog Retin Eye Res 2022:101097. [PMID: 35840488 DOI: 10.1016/j.preteyeres.2022.101097] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 05/31/2022] [Accepted: 06/29/2022] [Indexed: 11/18/2022]
Abstract
Alterations of the junctional complex of the outer blood-retinal barrier (oBRB), which is integrated by the close interaction of the retinal pigment epithelium, the Bruch's membrane, and the choriocapillaris, contribute to the loss of neuronal signalling and subsequent vision impairment in several retinal inflammatory disorders such as age-related macular degeneration and diabetic retinopathy. Reductionist approaches into the mechanisms that underlie such diseases have been hindered by the absence of adequate in vitro models using human cells to provide the 3D dynamic architecture that enables expression of the in vivo phenotype of the oBRB. Conventional in vitro cell models are based on 2D monolayer cellular cultures, unable to properly recapitulate the complexity of living systems. The main drawbacks of conventional oBRB models also emerge from the cell sourcing, the lack of an appropriate Bruch's membrane analogue, and the lack of choroidal microvasculature with flow. In the last years, the advent of organ-on-a-chip, bioengineering, and stem cell technologies is providing more advanced 3D models with flow, multicellularity, and external control over microenvironmental properties. By incorporating additional biological complexity, organ-on-a-chip devices can mirror physiologically relevant properties of the native tissue while offering additional set ups to model and study disease. In this review we first examine the current understanding of oBRB biology as a functional unit, highlighting the coordinated contribution of the different components to barrier function in health and disease. Then we describe recent advances in the use of pluripotent stem cells-derived retinal cells, Bruch's membrane analogues, and co-culture techniques to recapitulate the oBRB. We finally discuss current advances and challenges of oBRB-on-a-chip technologies for disease modelling.
Collapse
Affiliation(s)
- Blanca Molins
- Group of Ocular Inflammation: Clinical and Experimental Studies, Institut d'Investigacions Biomèdiques Agustí Pi I Sunyer (IDIBAPS), C/ Sabino de Arana 1, 08028, Barcelona, Spain.
| | - Marina Mesquida
- Group of Ocular Inflammation: Clinical and Experimental Studies, Institut d'Investigacions Biomèdiques Agustí Pi I Sunyer (IDIBAPS), C/ Sabino de Arana 1, 08028, Barcelona, Spain; Roche Pharma Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Basel, Switzerland
| | - Alfredo Adan
- Group of Ocular Inflammation: Clinical and Experimental Studies, Institut d'Investigacions Biomèdiques Agustí Pi I Sunyer (IDIBAPS), C/ Sabino de Arana 1, 08028, Barcelona, Spain; Instituto Clínic de Oftalmología, Hospital Clínic Barcelona, C/ Sabino de Arana 1, 08028, Barcelona, Spain
| |
Collapse
|
5
|
Dmitriev AV, Dmitriev AA, Linsenmeier RA. Extracellular K+ reflects light-evoked changes in retinal energy metabolism. Exp Eye Res 2022; 221:109133. [PMID: 35636490 PMCID: PMC10392107 DOI: 10.1016/j.exer.2022.109133] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 05/19/2022] [Accepted: 05/24/2022] [Indexed: 11/25/2022]
Abstract
Retinal neurons spend most of their energy to support the transmembrane movement of ions. Light-induced electrical activity is associated with a redistribution of ions, which affects the energy demand and results in a change in metabolism. Light-induced metabolic changes are expected to be different in distal and proximal retina due to differences in the light responses of different retinal cells. Extracellular K+ concentration ([K+]o) is a reliable indicator of local electrophysiological activity, and the purpose of this work was to compare [K+]o changes evoked by steady and flickering light in distal and proximal retina. Data were obtained from isolated mouse (C57Bl/6J) retinae. Double-barreled K+-selective microelectrodes were used to simultaneously record [K+]o and local ERGs. In the distal retina, photoreceptor hyperpolarization led to suppression of ion transfer, a decrease in [K+]o by 0.3-0.5 mM, reduced energy demand, and, as previously shown in vivo, decreased metabolism. Flickering light had the same effect on [K+]o in the distal retina as steady light of equivalent illumination. The conductance and voltage changes in postreceptor neurons are cell-specific, but the overall effect of steady light in the proximal retina is excitation, which is reflected in a [K+]o increase there (by a maximum of 0.2 mM). In steady light the [K+]o increase lasts only 1-2 s, but a sustained [K+]o increase is evoked by flickering light. A squarewave low frequency (1 Hz) flicker of photopic intensity produced the largest increases in [K+]o. Judging by measurements of [K+]o, steady illumination decreases energy metabolism in the distal retina, but not in the proximal retina (except for the first few seconds). Flickering light evokes the same decrease in the distal retina, but also evokes a sustained [K+]o increase in the proximal retina, suggesting an increase of metabolic demand there, especially at 1 Hz, when neurons of both on- and off-pathways appear to contribute maximally. This proximal retinal metabolic response to flicker correlates to the increase in blood flow during flicker that constitutes neurovascular coupling.
Collapse
|
6
|
Yazdani M. Uncontrolled Oxygen Levels in Cultures of Retinal Pigment Epithelium: Have We Missed the Obvious? Curr Eye Res 2022; 47:651-660. [PMID: 35243933 DOI: 10.1080/02713683.2022.2050264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Retinal pigment epithelium (RPE) is the outermost layer of retina located between the photoreceptor cells and the choroid. This highly-polarized monolayer provides critical support for the functioning of the other parts of the retina, especially photoreceptors. Methods of culturing RPE have been under development since its establishment in 1920s. Despite considering various factors, oxygen (O2) levels in RPE microenvironments during culture preparation and experimental procedure have been overlooked. O2 is a crucial parameter in the cultures, and therefore, maintaining RPE cells at O2 levels different from their native environment (70-90 mm Hg of O2) could have unintended consequences. Owing to the importance of the topic, lack of sufficient discussion in the literature and to encourage future research, this paper will focus on uncontrolled O2 level in cultures of RPE cells.
Collapse
Affiliation(s)
- Mazyar Yazdani
- Department of Medical Biochemistry, Oslo University Hospital, Rikshospitalet, 0027 Oslo, Norway
| |
Collapse
|
7
|
Age dependence of retinal vascular plexus attenuation in the triple transgenic mouse model of Alzheimer's disease. Exp Eye Res 2021; 214:108879. [PMID: 34896306 PMCID: PMC10155044 DOI: 10.1016/j.exer.2021.108879] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Revised: 11/17/2021] [Accepted: 11/30/2021] [Indexed: 12/16/2022]
Abstract
The influence of Alzheimer's disease (AD) progression and severity on the structural and functional integrity of the cerebral vasculature is well recognized. The retina is an extension of the brain; thus, changes in retinal vascular features may serve as markers of AD cerebrovascular pathologies. However, differentiating normal aging-versus AD-induced retinal vascular changes is unresolved. Therefore, we compared and quantified changes in superficial (SVP), intermediate (IVP), and deep (DVP) retinal vascular plexuses in young, middle-age, and old triple transgenic mouse model of AD (3xT-AD) to the changes that occur in age-matched controls (C57BL/6j). We used immunostaining combined with a novel tissue optical clearing approach along with a computational tool for quantitative analysis of vascular network alterations (vessel length and density) in SVP, IVP, and DVP. All three layers had comparable structural features and densities in young 3xTg-AD and control animals. In controls, IVP and DVP densities decreased with aging (-14% to -32% change from young to old, p < 0.05), while no changes were observed in SVP. In contrast, vascular parameters in the transgenic group decreased in all three layers with aging (-12% to -49% change from young to old, p < 0.05). Furthermore, in the old group, SVP and DVP vascular parameters were lower in the transgenics compared to age-matched controls (p < 0.05). Our analysis demonstrates that normal aging and progression of AD lead to various degrees of vascular alterations in the retina. Specifically, compared to normal aging, changes in vascular features of SVP and DVP regions of the retina are accelerated during AD progression. Considering recent advances in the field of depth-resolved imaging of retinal capillary network and microangiography, noninvasive quantitative monitoring of changes in retinal vascular network parameters of SVP and DVP may serve as markers for diagnosis and staging of Alzheimer's disease and discriminating AD-induced vascular attenuation from age-related vasculopathy.
Collapse
|
8
|
Tonade D, Kern TS. Photoreceptor cells and RPE contribute to the development of diabetic retinopathy. Prog Retin Eye Res 2021; 83:100919. [PMID: 33188897 PMCID: PMC8113320 DOI: 10.1016/j.preteyeres.2020.100919] [Citation(s) in RCA: 76] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Revised: 10/27/2020] [Accepted: 10/31/2020] [Indexed: 12/26/2022]
Abstract
Diabetic retinopathy (DR) is a leading cause of blindness. It has long been regarded as vascular disease, but work in the past years has shown abnormalities also in the neural retina. Unfortunately, research on the vascular and neural abnormalities have remained largely separate, instead of being integrated into a comprehensive view of DR that includes both the neural and vascular components. Recent evidence suggests that the most predominant neural cell in the retina (photoreceptors) and the adjacent retinal pigment epithelium (RPE) play an important role in the development of vascular lesions characteristic of DR. This review summarizes evidence that the outer retina is altered in diabetes, and that photoreceptors and RPE contribute to retinal vascular alterations in the early stages of the retinopathy. The possible molecular mechanisms by which cells of the outer retina might contribute to retinal vascular damage in diabetes also are discussed. Diabetes-induced alterations in the outer retina represent a novel therapeutic target to inhibit DR.
Collapse
Affiliation(s)
- Deoye Tonade
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA
| | - Timothy S Kern
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA; Veterans Administration Medical Center Research Service, Cleveland, OH, USA; Gavin Herbert Eye Institute, University of California Irvine, Irvine, CA, USA; Veterans Administration Medical Center Research Service, Long Beach, CA, USA.
| |
Collapse
|
9
|
Rahimi M, Leahy S, Matei N, Blair NP, Jeong S, Craft CM, Shahidi M. Assessment of inner retinal oxygen metrics and thickness in a mouse model of inherited retinal degeneration. Exp Eye Res 2021; 205:108480. [PMID: 33539865 DOI: 10.1016/j.exer.2021.108480] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 01/15/2021] [Accepted: 01/26/2021] [Indexed: 12/20/2022]
Abstract
The retinal degeneration 1 (rd1) mouse is a well-established model of inherited retinal degeneration, displaying photoreceptor degeneration and retinal vasculature damage. The purpose of the current study was to determine alterations in the rate of oxygen delivery from retinal circulation (DO2), the rate of oxygen extraction from the retinal circulation for metabolism (MO2), and oxygen extraction fraction (OEF) in rd1 mice. The study was performed in a total of 18 wild type (WT) and 10 rd1 mice at both 3-weeks and 12-weeks of age. Retinal arterial and venous oxygen contents (O2A and O2V) were measured using phosphorescence lifetime imaging. Total retinal blood flow (TRBF) was determined by fluorescence and red-free imaging. DO2 and MO2 were determined as TRBF × O2A and TRBF × (O2A-O2V), respectively. OEF was calculated as MO2/DO2. The thickness of individual retinal layers was measured from histology sections and inner retina (IR) and total retina (TR) thickness were calculated. TRBF, DO2 and MO2 were lower in rd1 mice compared to WT mice (P ≤ 0.001), whereas OEF was not significantly different between rd1 and WT mice (P = 0.4). TRBF and DO2 were lower at 3-weeks of age compared to 12-weeks of age (P ≤ 0.01), while MO2 was not significantly different between age groups (P = 0.4) and OEF was higher at 3-weeks of age compared to 12-weeks of age (P = 0.003). Additionally, the outer and inner retinal cell layer thicknesses were decreased in rd1 mice at 12-weeks of age compared to both age-matched WT mice and rd1 mice at 3-weeks of age (P ≤ 0.02). MO2 was directly correlated with both IR and TR thickness (R ≥ 0.50; P ≤ 0.03, N = 20). The findings indicate that the rate oxygen is supplied by the retinal circulation is decreased and the reduction in oxygen extracted for metabolism is related to retinal cell layer thinning in rd1 mice.
Collapse
Affiliation(s)
- Mansour Rahimi
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, USC Roski Eye Institute, Los Angeles, CA, USA
| | - Sophie Leahy
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, USC Roski Eye Institute, Los Angeles, CA, USA
| | - Nathanael Matei
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, USC Roski Eye Institute, Los Angeles, CA, USA
| | - Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Shinwu Jeong
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, USC Roski Eye Institute, Los Angeles, CA, USA
| | - Cheryl Mae Craft
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, USC Roski Eye Institute, Los Angeles, CA, USA; Department of Integrative Anatomical Sciences, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - Mahnaz Shahidi
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, USC Roski Eye Institute, Los Angeles, CA, USA.
| |
Collapse
|
10
|
Chen S, Moult EM, Zangwill LM, Weinreb RN, Fujimoto JG. Geometric Perfusion Deficits: A Novel OCT Angiography Biomarker for Diabetic Retinopathy Based on Oxygen Diffusion. Am J Ophthalmol 2021; 222:256-270. [PMID: 32918905 DOI: 10.1016/j.ajo.2020.09.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 08/13/2020] [Accepted: 09/02/2020] [Indexed: 12/26/2022]
Abstract
PURPOSE To develop geometric perfusion deficits (GPD), an optical coherence tomography angiography (OCTA) biomarker based on oxygen diffusion, and to evaluate its utility in a pilot study of healthy subjects and patients with diabetic retinopathy (DR). DESIGN Retrospective cross-sectional study. METHODS Commercial spectral-domain optical coherence tomography angiography (OCTA) instruments were used to acquire repeated 3 × 3-mm2 and 6 × 6-mm2 motion-corrected macular OCTA volumes. En face OCTA images corresponding to the superficial capillary plexus (SCP), deep capillary plexus (DCP), and full retinal projections were obtained using automatic segmentation. For each projection, the GPD percentage and the vessel density percentage, the control metric, were computed, and their values were compared between the normal and DR eyes. The repeated OCTA acquisitions were used to assess the test-retest repeatability of the GPD and vessel density percentages. RESULTS Repeated OCTA scans of 15 normal eyes and 12 DR eyes were obtained. For all en face projections, GPD percentages were significantly higher in DR eyes than in normal eyes; vessel density percentages were significantly lower in all but 1 projection (DCP). Large GPD areas were used to identify focal perfusion deficits. Test-retest analysis showed that the GPD percentage had superior repeatability than the vessel density percentage in most cases. A strong negative correlation between the GPD percentage and the vessel density percentage was also found. CONCLUSIONS Geometric perfusion deficits, an OCTA biomarker based on oxygen diffusion, provides a quantitative metric of macular microvascular remodeling with a strong physiological underpinning. The GPD percentage may serve as a useful biomarker for detecting and monitoring DR.
Collapse
|
11
|
Hass DT, Barnstable CJ. Uncoupling proteins in the mitochondrial defense against oxidative stress. Prog Retin Eye Res 2021; 83:100941. [PMID: 33422637 DOI: 10.1016/j.preteyeres.2021.100941] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 12/28/2020] [Accepted: 01/03/2021] [Indexed: 02/06/2023]
Abstract
Oxidative stress is a major component of most major retinal diseases. Many extrinsic anti-oxidative strategies have been insufficient at counteracting one of the predominant intrinsic sources of reactive oxygen species (ROS), mitochondria. The proton gradient across the inner mitochondrial membrane is a key driving force for mitochondrial ROS production, and this gradient can be modulated by members of the mitochondrial uncoupling protein (UCP) family. Of the UCPs, UCP2 shows a widespread distribution and has been shown to uncouple oxidative phosphorylation, with concomitant decreases in ROS production. Genetic studies using transgenic and knockout mice have documented the ability of increased UCP2 activity to provide neuroprotection in models of a number of diseases, including retinal diseases, indicating that it is a strong candidate for a therapeutic target. Molecular studies have identified the structural mechanism of action of UCP2 and have detailed the ways in which its expression and activity can be controlled at the transcriptional, translational and posttranslational levels. These studies suggest a number of ways in control of UCP2 expression and activity can be used therapeutically for both acute and chronic conditions. The development of such therapeutic approaches will greatly increase the tools available to combat a broad range of serious retinal diseases.
Collapse
Affiliation(s)
- Daniel T Hass
- Department of Biochemistry, The University of Washington, Seattle, WA, 98109, USA
| | - Colin J Barnstable
- Department of Neural and Behavioral Sciences, The Pennsylvania State University, Hershey, PA, 17033, USA.
| |
Collapse
|
12
|
Intravenous ketamine for long term anesthesia in rats. Heliyon 2020; 6:e05686. [PMID: 33367124 PMCID: PMC7749388 DOI: 10.1016/j.heliyon.2020.e05686] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 10/15/2020] [Accepted: 12/04/2020] [Indexed: 11/22/2022] Open
Abstract
Ketamine/xylazine anesthesia has been used primarily for short term procedures in animals, but two prior reports used intravenous ketamine/xylazine for experiments taking many hours. However, there is a discrepancy about the appropriate dose, which is resolved here. Adult Long-Evans rats were used for recording from the retina. Doses of Ketamine/xylazine were adjusted to minimize anesthetic in terminal experiments lasting 10 h. An allometric relation was fitted to the resulting data on doses as a function of body weight, and compared to prior work. The allometric relationship between the continuously infused specific dose and weight was: dose = 9.13 (weight)−1.213 (r2 = 0.73), where dose is in mg-kg−1-hr−1 and rat weight is in kg. The dose of xylazine was 3.3% of the ketamine dose. No attempt was made to explore different relative doses of xylazine and ketamine. Prior work is consistent with this relationship, showing that the earlier discrepancy resulted from using rats of different sizes. Ketamine at the doses used here still depressed the electroretinogram relative to historical controls using urethane. We conclude that intravenous ketamine dosing in rats should not use the same mg-kg−1-hr−1 dose for all rats, but take into account the strong allometric relationship between dose and rat weight. There is an advantage in using smaller doses in order to prevent unnecessary depression of neural responses.
Collapse
|
13
|
Zhao T, Chen Y, Liu D, Stewart JM. Optical Coherence Tomography Angiography Assessment of Macular Choriocapillaris and Choroid Following Panretinal Photocoagulation in a Diverse Population With Advanced Diabetic Retinopathy. Asia Pac J Ophthalmol (Phila) 2020; 10:203-207. [PMID: 33181550 DOI: 10.1097/apo.0000000000000345] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
PURPOSE The aim of this study was to evaluate choroidal and retinal microvasculature with optical coherence tomography angiography (OCTA) after panretinal photocoagulation (PRP) for diabetic retinopathy in a primarily Hispanic and Asian population. DESIGN Retrospective study. METHODS Eyes were examined by OCTA in the macula (3 × 3 mm) just before PRP treatment and 1 to 3 months afterwards. Choroidal thickness (CT) and central retinal thickness (CRT) were measured. Choroidal flow signal voids (CFSV) and choriocapillaris flow signal voids (CCFSV) were acquired. Retinal microvasculature parameters, including superficial and deep vessel density, superficial and deeper perfusion density, foveal avascular zone area, perimeter and circularity, were calculated. Ocular examinations and demographic information were analyzed. RESULTS CT at a location 1000 μm temporal to the fovea increased significantly after PRP (from 278.64 μm to 313.44 μm, P = 0.026). CCFSV increased slightly from (46.72 ± 8.52)% to (47.07 ± 10.77)%, but the difference was not statistically significant (P = 0.782). A similar finding was observed in CFSV (increase from 35.81% to 36.64%, P = 0.165). The change in all retinal microvasculature parameters was also not significant. Best-corrected visual acuity (BCVA) decreased from 0.218 ± 0.153 to 0.262 ± 0.147 (P = 0.034). Increased CRT (from 245.41 ± 33.18 μm to 251.14 ± 38.97 μm, P = 0.007) was observed. The change in CRT positively correlated with pre-PRP CRT (r = 0.434, P = 0.019) and BCVA reduction (r = 0.418, P = 0.024). Neither BCVA reduction nor CRT increase correlated with OCTA metrics. CONCLUSIONS OCTA demonstrates redistribution of choroidal circulation from the periphery to the macula after PRP, with increased macular CT and stable choroidal blood flow density. Eyes with greater macular thickness are more likely to experience an increase in CRT.
Collapse
Affiliation(s)
- Tong Zhao
- University of California, San Francisco, Department of Ophthalmology, San Francisco, CA, USA
- Department of Ophthalmology, Zuckerberg San Francisco General Hospital and Trauma Center, San Francisco, CA
- China-Japan Friendship Hospital, Department of Ophthalmology, Beijing, China
| | - Yi Chen
- University of California, San Francisco, Department of Ophthalmology, San Francisco, CA, USA
- Department of Ophthalmology, Zuckerberg San Francisco General Hospital and Trauma Center, San Francisco, CA
- Shenzhen Key Laboratory of Ophthalmology, Shenzhen Eye Hospital, Jinan University, School of Optometry, Shenzhen University, Shenzhen, China
| | - Dongwei Liu
- University of California, San Francisco, Department of Ophthalmology, San Francisco, CA, USA
- Department of Ophthalmology, Zuckerberg San Francisco General Hospital and Trauma Center, San Francisco, CA
- Department of Ophthalmology, The Second Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Jay M Stewart
- University of California, San Francisco, Department of Ophthalmology, San Francisco, CA, USA
- Department of Ophthalmology, Zuckerberg San Francisco General Hospital and Trauma Center, San Francisco, CA
| |
Collapse
|
14
|
Retinal capillary oximetry with visible light optical coherence tomography. Proc Natl Acad Sci U S A 2020; 117:11658-11666. [PMID: 32398376 DOI: 10.1073/pnas.1918546117] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Assessing oxygen saturation (sO2) remains challenging but is nonetheless necessary for understanding retinal metabolism. We and others previously achieved oximetry on major retinal vessels and measured the total retinal oxygen metabolic rate in rats using visible-light optical coherence tomography. Here we extend oximetry measurements to capillaries and investigate all three retinal vascular plexuses by amplifying and extracting the spectroscopic signal from each capillary segment under the guidance of optical coherence tomography (OCT) angiography. Using this approach, we measured capillary sO2 in the retinal circulation in rats, demonstrated reproducibility of the results, validated the measurements in superficial capillaries with known perfusion pathways, and determined sO2 responses to hypoxia and hyperoxia in the different retinal capillary beds. OCT capillary oximetry has the potential to provide new insights into the retinal circulation in the normal eye as well as in retinal vascular diseases.
Collapse
|
15
|
Kubota R, Calkins DJ, Henry SH, Linsenmeier RA. Emixustat Reduces Metabolic Demand of Dark Activity in the Retina. Invest Ophthalmol Vis Sci 2020; 60:4924-4930. [PMID: 31770432 DOI: 10.1167/iovs.19-28194] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose In the dark, photoreceptor outer segments contain high levels of cyclic guanosine 3'-5' monophosphate (cGMP), which binds to ion channels, holding them open and allowing an influx of cations. Ion pumping activity, which balances cation influx, uses considerable amounts of adenosine triphosphate (ATP) and oxygen. Light reduces cation influx and thereby lowers metabolic demand. Blood vessels are compromised in the diabetic retina and may not be able to meet the higher metabolic demand in darkness. Emixustat is a visual cycle modulator (VCM) that reduces chromophore levels and, therefore, may mimic light conditions. We evaluated the effect of emixustat on oxygen consumption and cation influx in dark conditions. Methods Cation influx was measured in rats using Mn2+-magnetic resonance imaging (MEMRI). Retinal oxygen profiles were recorded to evaluate oxygen consumption. In the MEMRI protocol, animals were treated with either emixustat or vehicle. In the oxygen protocol, animals were untreated or treated with emixustat. Results In vehicle-treated animals, cation channel activity increased in the dark. Emixustat treatment reduced cation channel activity; activity was comparable to vehicle-treated controls in light conditions. In vehicle-treated animals, minimum retinal oxygen tension decreased as the retina recovered from a photobleach, indicating that more oxygen was being consumed. Emixustat treatment prevented the decrease in oxygen pressure after photobleach. Conclusions Emixustat reduced the cation influx and retinal oxygen consumption associated with dark conditions. VCMs are a promising potential treatment for ischemic retinal neovascularization, such as that in diabetic retinopathy.
Collapse
Affiliation(s)
- Ryo Kubota
- Acucela, Inc., Seattle, Washington, United States
| | - David J Calkins
- Department of Ophthalmology and Visual Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, United States
| | | | - Robert A Linsenmeier
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, United States.,Department of Neurobiology, Northwestern University, Evanston, Illinois, United States
| |
Collapse
|
16
|
Fawzi AA, Fayed AE, Linsenmeier RA, Gao J, Yu F. Improved Macular Capillary Flow on Optical Coherence Tomography Angiography After Panretinal Photocoagulation for Proliferative Diabetic Retinopathy. Am J Ophthalmol 2019; 206:217-227. [PMID: 31078542 DOI: 10.1016/j.ajo.2019.04.032] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Revised: 04/25/2019] [Accepted: 04/26/2019] [Indexed: 11/25/2022]
Abstract
PURPOSE This study evaluated the macular microvascular changes in eyes with proliferative diabetic retinopathy (PDR) following panretinal photocoagulation (PRP). DESIGN Using optical coherence tomographic angiography (OCTA), we prospectively studied 10 eyes of 10 subjects with high-risk PDR immediately before, at 1 month, and at 3-6 months following PRP, using a 3- × 3-mm OCTA scan at each visit. METHODS The following parameters were calculated for the superficial (SCP), middle (MCP), and deep capillary plexuses (DCP): parafoveal vessel density (VD), adjusted flow index (AFI), and percent area of nonperfusion (PAN). Parafoveal SCP vessel-length density (VLD) was also evaluated. We performed univariate and multivariable statistics, adjusting for age and signal strength. To model the hemodynamic effect of PRP, we also present a mathematical model based on electrical circuits. RESULTS We found no significant difference for the vascular density parameters following PRP, except for decreased density at the MCP at the latest timepoint in the adjusted multivariable model. PAN, a metric of nonperfusion adjusted for noise, and AFI, a surrogate metric of blood flow, showed significant increases at all capillary levels in the adjusted model. Our mathematical model explained how PRP would increase macular blood flow. CONCLUSIONS Using OCTA, we found an overall increase in the flow metrics of all capillary layers in the macula following PRP, unrelated to macular edema or thickening, in line with the mathematical model. Our results suggest an overall redistribution of blood flow to the posterior pole following PRP, adding a new dimension to our understanding of the complex biologic effects of PRP in PDR. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.
Collapse
|
17
|
Dmitriev AV, Henderson D, Linsenmeier RA. Diabetes Alters pH Control in Rat Retina. Invest Ophthalmol Vis Sci 2019; 60:723-730. [PMID: 30786276 PMCID: PMC6383832 DOI: 10.1167/iovs.18-26073] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Purpose The purpose of this study was to determine whether the ability of the rat retina to control its pH is affected by diabetes. Methods Double-barreled H+-selective microelectrodes were used to measure extracellular [H+] in the dark-adapted retina of intact control and diabetic Long-Evans rats 1 to 6 months after intraperitoneal injection of vehicle or streptozotocin, respectively. Two manipulations-increasing of blood glucose and intravenous injection of the carbonic anhydrase blocker dorzolamide (DZM)-were used to examine their effects on retinal pH regulation. Results An increase of retinal acidity was correlated with the diabetes-related increase in blood glucose, but only between 1 and 3 months of diabetes, not earlier or later. Adding intravenous glucose had no noticeable effect on the retinal acidity of control animals. In contrast, similar injections of glucose in diabetic rats significantly increased the acidity of the retina. Again, the largest increase of retinal acidity due to artificially elevated blood glucose was observed at 1 to 3 months of diabetes. Suppression of carbonic anhydrase by DZM dramatically increased the retinal acidity in both control and diabetic retinas to a similar degree. However, in controls, the strongest effect of DZM was recorded within 10 minutes after the injection, but in diabetics, the effect tended to increase with time and after 2 hours could be two to three times larger than at the beginning. Conclusions During development of diabetes in rats, the control over retinal pH is partly compromised so that conditions that perturb retinal pH lead to larger and/or more sustained changes than in control animals.
Collapse
Affiliation(s)
- Andrey V Dmitriev
- Biomedical Engineering Department, Northwestern University, Evanston, Illinois, United States
| | - Desmond Henderson
- Biomedical Engineering Department, Northwestern University, Evanston, Illinois, United States
| | - Robert A Linsenmeier
- Biomedical Engineering Department, Northwestern University, Evanston, Illinois, United States.,Neurobiology Department, Northwestern University, Evanston, Illinois, United States.,Ophthalmology Department, Northwestern University, Chicago, Illinois, United States
| |
Collapse
|
18
|
Şencan İ, Esipova TV, Yaseen MA, Fu B, Boas DA, Vinogradov SA, Shahidi M, Sakadžić S. Two-photon phosphorescence lifetime microscopy of retinal capillary plexus oxygenation in mice. JOURNAL OF BIOMEDICAL OPTICS 2018; 23:1-9. [PMID: 30516039 PMCID: PMC6278707 DOI: 10.1117/1.jbo.23.12.126501] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 11/07/2018] [Indexed: 05/23/2023]
Abstract
Impaired oxygen delivery and/or consumption in the retinal tissue underlies the pathophysiology of many retinal diseases. However, the essential tools for measuring oxygen concentration in retinal capillaries and studying oxygen transport to retinal tissue are still lacking. We show that two-photon phosphorescence lifetime microscopy can be used to map absolute partial pressures of oxygen (pO2) in the retinal capillary plexus. Measurements were performed at various retinal depths in anesthetized mice under systemic normoxic and hyperoxic conditions. We used a newly developed two-photon phosphorescent oxygen probe, based on a two-photon absorbing platinum tetraphthalimidoporphyrin, and commercially available optics without correction for optical aberrations of the eye. The transverse and axial distances within the tissue volume were calibrated using a model of the eye's optical system. We believe this is the first demonstration of in vivo depth-resolved imaging of pO2 in retinal capillaries. Application of this method has the potential to advance our understanding of oxygen delivery on the microvascular scale and help elucidate mechanisms underlying various retinal diseases.
Collapse
Affiliation(s)
- İkbal Şencan
- Massachusetts General Hospital, Harvard Medical School, Athinuola A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
| | - Tatiana V. Esipova
- University of Pennsylvania, Departments of Biochemistry and Biophysics and of Chemistry, Philadelphia, Pennsylvania, United States
| | - Mohammad A. Yaseen
- Massachusetts General Hospital, Harvard Medical School, Athinuola A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
| | - Buyin Fu
- Massachusetts General Hospital, Harvard Medical School, Athinuola A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
| | - David A. Boas
- Massachusetts General Hospital, Harvard Medical School, Athinuola A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
- Boston University, Department of Biomedical Engineering, Boston, Massachusetts, United States
| | - Sergei A. Vinogradov
- University of Pennsylvania, Departments of Biochemistry and Biophysics and of Chemistry, Philadelphia, Pennsylvania, United States
| | - Mahnaz Shahidi
- University of Southern California, Departments of Ophthalmology and Biomedical Engineering, Los Angeles, California, United States
| | - Sava Sakadžić
- Massachusetts General Hospital, Harvard Medical School, Athinuola A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
| |
Collapse
|
19
|
Son T, Alam M, Toslak D, Wang B, Lu Y, Yao X. Functional optical coherence tomography of neurovascular coupling interactions in the retina. JOURNAL OF BIOPHOTONICS 2018; 11:e201800089. [PMID: 29770594 PMCID: PMC6239985 DOI: 10.1002/jbio.201800089] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 05/15/2018] [Indexed: 05/19/2023]
Abstract
Quantitative evaluation of retinal neurovascular coupling is essential for a better understanding of visual function and early detection of eye diseases. However, there is no established method to monitor coherent interactions between stimulus-evoked neural activity and hemodynamic responses at high resolution. Here, we report a multimodal functional optical coherence tomography (OCT) imaging methodology to enable concurrent intrinsic optical signal (IOS) imaging of stimulus-evoked neural activity and hemodynamic responses at capillary resolution. OCT angiography guided IOS analysis was used to separate neural-IOS and hemodynamic-IOS changes in the same retinal image sequence. Frequency flicker stimuli evoked neural-IOS changes in the outer retina; that is, photoreceptor layer, first and then in the inner retina, including outer plexus layer (OPL), inner plexiform layer (IPL), and ganglion cell layer (GCL), which were followed by hemodynamic-IOS changes primarily in the inner retina; that is, OPL, IPL, and GCL. Different time courses and signal magnitudes of hemodynamic-IOS responses were observed in blood vessels with various diameters.
Collapse
Affiliation(s)
- Taeyoon Son
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Minhaj Alam
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Devrim Toslak
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
- Department of Ophthalmology, Antalya Training and Research Hospital, Antalya, Turkey
| | - Benquan Wang
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Yiming Lu
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Xincheng Yao
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL 60612, USA
| |
Collapse
|
20
|
Laíns I, Gantner M, Murinello S, Lasky-Su JA, Miller JW, Friedlander M, Husain D. Metabolomics in the study of retinal health and disease. Prog Retin Eye Res 2018; 69:57-79. [PMID: 30423446 DOI: 10.1016/j.preteyeres.2018.11.002] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 10/06/2018] [Accepted: 11/07/2018] [Indexed: 02/06/2023]
Abstract
Metabolomics is the qualitative and quantitative assessment of the metabolites (small molecules < 1.5 kDa) in body fluids. The metabolites are the downstream of the genetic transcription and translation processes and also downstream of the interactions with environmental exposures; thus, they are thought to closely relate to the phenotype, especially for multifactorial diseases. In the last decade, metabolomics has been increasingly used to identify biomarkers in disease, and it is currently recognized as a very powerful tool with great potential for clinical translation. The metabolome and the associated pathways also help improve our understanding of the pathophysiology and mechanisms of disease. While there has been increasing interest and research in metabolomics of the eye, the application of metabolomics to retinal diseases has been limited, even though these are leading causes of blindness. In this manuscript, we perform a comprehensive summary of the tools and knowledge required to perform a metabolomics study, and we highlight essential statistical methods for rigorous study design and data analysis. We review available protocols, summarize the best approaches, and address the current unmet need for information on collection and processing of tissues and biofluids that can be used for metabolomics of retinal diseases. Additionally, we critically analyze recent work in this field, both in animal models and in human clinical disease, including diabetic retinopathy and age-related macular degeneration. Finally, we identify opportunities for future research applying metabolomics to improve our current assessment and understanding of mechanisms of vitreoretinal diseases, and to hence improve patient assessment and care.
Collapse
Affiliation(s)
- Inês Laíns
- Retina Service, Massachusetts Eye and Ear, Harvard Medical School, 243 Charles Street, Boston, MA, 02114, United States; Faculty of Medicine, University of Coimbra, 3000 Coimbra, Portugal.
| | - Mari Gantner
- Lowy Medical Research Institute, La Jolla, CA, 92037, United States; Scripps Research Institute, La Jolla, CA, 92037, United States.
| | - Salome Murinello
- Lowy Medical Research Institute, La Jolla, CA, 92037, United States; Scripps Research Institute, La Jolla, CA, 92037, United States.
| | - Jessica A Lasky-Su
- Systems Genetics and Genomics Unit, Channing Division of Network Medicine Brigham and Women's Hospital and Harvard Medical School, 75 Francis Street, Boston, MA, 02115, United States.
| | - Joan W Miller
- Retina Service, Massachusetts Eye and Ear, Harvard Medical School, 243 Charles Street, Boston, MA, 02114, United States.
| | - Martin Friedlander
- Lowy Medical Research Institute, La Jolla, CA, 92037, United States; Scripps Research Institute, La Jolla, CA, 92037, United States.
| | - Deeba Husain
- Retina Service, Massachusetts Eye and Ear, Harvard Medical School, 243 Charles Street, Boston, MA, 02114, United States.
| |
Collapse
|
21
|
Abstract
PURPOSE Continuous peripheral pulse oximetry for monitoring adequacy of oxygenation is probably the most important technological advance for patients' monitoring and safety in the last decades. Pulse oximetry has the disadvantage of measuring the peripheral circulation, and the only mean to measure oxygen content of the central circulation is by invasive technology. Determination of blood oxyhaemoglobin saturation in the retinal vessels of the eye can be achieved noninvasively through spectrophotometric retinal oximetry which provides access to the central nervous system circulation. The aim of the thesis was to determine whether retinal oximetry technique can be applied for estimation of the central nervous system circulation which until now has only been possible invasively. This was achieved by measuring oxyhaemoglobin saturation in three adult subject study groups: in people with central retinal vein occlusion (CRVO) to observe local tissue hypoxia, in patients with severe chronic obstructive pulmonary disease (COPD) on long-term oxygen therapy to observe systemic hypoxaemia and in healthy subjects during hyperoxic breathing to observe systemic hyperoxemia. In addition, the fourth study that is mentioned was performed to test whether retinal oximetry is feasible for neonates. METHODS Retinal oximetry in central retinal vein occlusion: Sixteen subjects with central retinal vein occlusion participated in the study. The oxyhaemoglobin saturation of the central retinal vein occlusion affected eye was compared with the fellow unaffected eye. Retinal oximetry in healthy people under hyperoxia: Thirty healthy subjects participated in the study, and the oxyhaemoglobin saturation of retinal arterioles and venules was compared between normoxic and hyperoxic breathing. Retinal oximetry in severe chronic obstructive pulmonary disease: Eleven patients with severe chronic obstructive pulmonary disease participated in the study. Retinal oximetry measurements were made with and without their daily supplemental oxygen therapy. Retinal arteriolar oxyhaemoglobin saturation when inspiring ambient air was compared with blood samples from the radial artery and finger pulse oximetry and healthy controls. The healthy control group was assembled from our database for comparison of oxyhaemoglobin saturation of retinal arterioles and venules during the ambient air breathing. The retinal oximeter is based on a conventional fundus camera and a specialized software. A beam splitter coupled with two high-resolution digital cameras allows for simultaneous acquisition of retinal images at separative wavelengths for calculation of oxyhaemoglobin saturation. In addition, retinal images of 28 full-term healthy neonates were obtained with scanning laser ophthalmoscope combined with modified Oxymap analysis software for calculation of the optical density ratio and vessel diameter RESULTS: Retinal oximetry in central retinal vein occlusion: Mean retinal venous oxyhaemoglobin saturation was 31 ± 12% in CRVO eyes and 52 ± 11% in unaffected fellow eyes (mean ± SD, n = 14, p < 0.0001). The arteriovenous oxygen difference (AV-difference) was 63 ± 11% in CRVO eyes and 43 ± 7% in fellow eyes (p < 0.0001). The variability of retinal venous oxyhaemoglobin saturation was considerable within and between eyes affected by CRVO. There was no difference in oxyhaemoglobin saturation of retinal arterioles between the CRVO eyes and the unaffected eyes (p = 0.49). Retinal oximetry in healthy people under hyperoxia: During hyperoxic breathing, the oxyhaemoglobin saturation in retinal arterioles increased to 94.5 ± 3.8% as compared with 92.0 ± 3.7% at baseline (n = 30, p < 0.0001). In venules, the mean oxyhaemoglobin saturation increased to 76.2 ± 8.0% from 51.3 ± 5.6% (p < 0.0001) at baseline. The AV-difference was markedly lower during hyperoxic breathing as compared with the normoxic breathing (18.3 ± 9.0% versus 40.7 ± 5.7%, p < 0.0001). Retinal oximetry in severe chronic obstructive pulmonary disease: During ambient air breathing, chronic obstructive pulmonary disease subjects had significantly lower oxyhaemoglobin saturation than healthy controls in both retinal arterioles (87.2 ± 4.9% versus 93.4 ± 4.3%, p = 0.02, n = 11) and venules (45.0 ± 10.3% versus 55.2 ± 5.5%, p = 0.01) but the AV-difference was not markedly different (p = 0.17). Administration of their prescribed oxygen therapy significantly increased the oxyhaemoglobin saturation in retinal arterioles (87.2 ± 4.9% to 89.5 ± 6.0%, p = 0.02) but not in venules (45.0 ± 10.3% to 46.7 ± 12.8%, p = 0.3). Retinal oximetry values were slightly lower than finger pulse oximetry (mean percentage points difference = -3.1 ± 5.5) and radial artery blood values (-5.0 ± 5.4). Retinal oximetry study in neonates: The modified version of the retinal oximetry instrument estimated the optical density ratio in retinal arterioles to be 0.256 ± 0.041 that was significantly different from the 0.421 ± 0.089 in venules (n = 28, p < 0.001, paired t-test). The vascular diameter of retinal arterioles was markedly narrower than of venules (14.1 ± 2.7 and 19.7 ± 3.7 pixels, p < 0.001). CONCLUSION The results of this thesis indicate that spectrophotometric retinal oximetry is sensitive to both local and systemic changes in oxyhaemoglobin saturation. Retinal oxyhaemoglobin saturation values are slightly lower than radial artery blood sample and finger pulse oximetry values. The discrepancies between the different modalities are expected to derive from countercurrent exchange between central retinal artery and vein within the optic nerve but calibration issues cannot be excluded as contributing to this difference. Despite these differences, the findings indicate the potential of retinal oximetry for noninvasive real-time measurements of oxyhaemoglobin saturation in central nervous system vessels. Following calibration upgrade and technological improvement, verification retinal oximetry may potentially be applied to critically ill and anaesthesia care patients. The study on combined scanning laser ophthalmoscope and retinal oximetry supports the feasibility of the technique for oximetry analysis in newly born babies.
Collapse
|
22
|
Blair NP, Tan MR, Felder AE, Teng PY, Wanek J, Shahidi M. Retinal tissue oxygen tension and consumption during light flicker stimulation in rat. Exp Eye Res 2018; 175:207-211. [PMID: 30121195 DOI: 10.1016/j.exer.2018.08.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 08/09/2018] [Accepted: 08/12/2018] [Indexed: 10/28/2022]
Abstract
Light flicker stimulation has been shown to increase inner retinal oxygen metabolism and supply. The purpose of the study was to test the hypothesis that sustained light flicker stimulation of various durations alters the depth profile metrics of oxygen partial pressure in the retinal tissue (tPO2) but not the outer retinal oxygen consumption rate (QO2). In 17 rats, tPO2 depth profiles were derived by phosphorescence lifetime imaging after intravitreal injection of an oxyphor. tPO2 profile metrics, including mean inner retinal tPO2, maximum outer retinal tPO2 and minimum outer retinal tPO2 were determined. QO2 was calculated using a one-dimensional oxygen diffusion model. Data were acquired at baseline (constant light illumination) and during light flicker stimulation at 10 Hz under the same mean illumination levels, and differences between values obtained during flicker and baseline were calculated. None of the tPO2 profile metrics or QO2 differences depended on the duration of light flicker stimulation (R2 ≤ 0.03). No significant change in any of the tPO2 profile metrics was detected with light flicker compared with constant light (P ≥ 0.08). Light flicker decreased QO2 from 0.53 ± 0.29 to 0.38 ± 0.30 mL O2/(min*100 gm), a reduction of 28% (P = 0.02). The retinal compensatory responses to the physiologic challenge of light flicker stimulation were effective in maintaining the levels of oxygen at or near baseline in the inner retina. Oxygen availability to the inner retina during light flicker may also have been enhanced by the decrease in QO2.
Collapse
Affiliation(s)
- Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Michael R Tan
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Anthony E Felder
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Pang-Yu Teng
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Justin Wanek
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Mahnaz Shahidi
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| |
Collapse
|
23
|
Nesper PL, Fawzi AA. Human Parafoveal Capillary Vascular Anatomy and Connectivity Revealed by Optical Coherence Tomography Angiography. Invest Ophthalmol Vis Sci 2018; 59:3858-3867. [PMID: 30073360 PMCID: PMC6071478 DOI: 10.1167/iovs.18-24710] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 07/07/2018] [Indexed: 11/24/2022] Open
Abstract
Purpose To assess the connection among arterioles, venules, and capillaries in three retinal capillary plexuses using optical coherence tomography angiography (OCTA). Methods This was a prospective, cross-sectional, observational study including 20 eyes of 10 healthy subjects. En face and cross-sectional OCTA images were segmented to study the superficial (SCP), middle (MCP), and deep capillary plexuses (DCP). Using thin slabs and manual segmentation within the three plexuses, we examined the connections between the large-caliber superficial vessels within a 3 × 3 mm2 OCTA scan (arterioles and venules) and the smaller capillaries in each plexus. Results Twenty eyes of 10 healthy subjects (5 females; average age of 30.8 ± 6.3 years) were included in the analysis. We identified vascular interconnections linking the superficial arterioles and venules with capillaries in each plexus (SCP, MCP, and DCP). We found capillaries in the DCP crossed the horizontal raphe. Conclusions Our findings show that each of the three capillary plexuses in the parafovea has its own feeding arteriolar supply and draining venules, supporting a physiologic model in which each plexus controls its own oxygenated blood supply to match the metabolic needs of each distinct retinal neurovascular unit.
Collapse
Affiliation(s)
- Peter L. Nesper
- The Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
| | - Amani A. Fawzi
- The Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
| |
Collapse
|
24
|
Soetikno BT, Beckmann L, Zhang X, Fawzi AA, Zhang HF. Visible-light optical coherence tomography oximetry based on circumpapillary scan and graph-search segmentation. BIOMEDICAL OPTICS EXPRESS 2018; 9:3640-3652. [PMID: 30338145 PMCID: PMC6191632 DOI: 10.1364/boe.9.003640] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 06/25/2018] [Accepted: 06/25/2018] [Indexed: 05/18/2023]
Abstract
Visible-light optical coherence tomography (vis-OCT) enables retinal oximetry by measuring the oxygen saturation of hemoglobin (sO2) from within individual retinal blood vessels. The sO2 calculation requires reliable estimation of the true spectrum of backscattered light from the posterior vessel wall. Unfortunately, subject motion and image noise make averaging from multiple A-lines at the same depth position challenging, and lead to inaccurate sO2 estimation. In this study, we developed an algorithm to reliably extract the backscattered light's spectrum. We used circumpapillary scanning to sample the vessels repeatedly at the same location. A combination of cross-correlation and graph-search based segmentation extracted the posterior wall locations. Using measurements from 100 B-scans as a gold standard, we demonstrated that our method achieved highly accurate measures of sO2 with minimal bias. In addition, we also investigated how the number of repeated measurements affects the accuracy of sO2 measurement. Our method sets the stage for large-scale studies of retinal oxygenation in animals and humans.
Collapse
Affiliation(s)
- Brian T. Soetikno
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
- Department of Ophthalmology, Northwestern University, Chicago, IL, USA
- Medical Scientist Training Program, Northwestern University, Chicago, IL, USA
| | - Lisa Beckmann
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Xian Zhang
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
| | - Amani A. Fawzi
- Department of Ophthalmology, Northwestern University, Chicago, IL, USA
| | - Hao F. Zhang
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA
- Department of Ophthalmology, Northwestern University, Chicago, IL, USA
| |
Collapse
|
25
|
OCT Angiography Changes in the 3 Parafoveal Retinal Plexuses in Response to Hyperoxia. Ophthalmol Retina 2017; 2:329-336. [PMID: 29888339 DOI: 10.1016/j.oret.2017.07.022] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Purpose Use projection-resolved OCT angiography to investigate the autoregulatory response in the 3 parafoveal retinal plexuses under hyperoxia. Design Prospective cohort study. Participants Nine eyes from 9 healthy participants. Methods One eye from each participant was scanned using a commercial spectral-domain OCT system. Two repeated macular scans (3 × 3 mm2) were acquired at baseline and during oxygen breathing. The split-spectrum amplitude-decorrelation algorithm was used to detect blood flow. The projection-resolved algorithm was used to suppress projection artifacts and resolve blood flow in 3 distinct parafoveal plexuses. The Wilcoxon signed-rank test was used to compare baseline and hyperoxic parameters. The coefficient of variation, intraclass correlation coefficient, and pooled standard deviation were used to assess the reliability of OCT angiography measurements. Main Outcome Measures Flow index and vessel density were calculated from the en face angiograms of each of the 3 plexuses, as well as from the all-plexus inner retinal slab. Results Hyperoxia induced significant reduction in the flow index (-11%) and vessel density (-7.8%) of only the deep capillary plexus (P < 0.001) and in the flow index of the all-plexus slab (P = 0.015). The flow index also decreased in the intermediate capillary plexus and the superficial vascular complex, but these changes were small and not statistically significant. The projection-resolved OCT angiography showed good within-session baseline repeatability (coefficient of variation, 0.8%-5.2%; intraclass correlation coefficient, 0.93-0.98) in all parameters. Relatively large between-day response reproducibility was observed (pooled standard deviation, 1.7%-9.4%). Conclusions Projection-resolved OCT angiography was able to show that the retinal autoregulatory response to hyperoxia affects only the deep capillary plexus, but not the intermediate capillary plexus or superficial vascular complex.
Collapse
|
26
|
Felder AE, Wanek J, Teng PY, Blair NP, Shahidi M. A method for volumetric retinal tissue oxygen tension imaging. Curr Eye Res 2017; 43:122-127. [PMID: 28956656 DOI: 10.1080/02713683.2017.1373823] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
PURPOSE Inadequate retinal oxygenation occurs in many vision-threatening retinal diseases, including diabetic retinopathy, retinal vascular occlusions, and age-related macular degeneration. Therefore, techniques that assess retinal oxygenation are necessary to understand retinal physiology in health and disease. The purpose of the current study is to report a method for the three-dimensional (3D) imaging of retinal tissue oxygen tension (tPO2) in rats. METHODS Imaging was performed in Long Evans pigmented rats under systemic normoxia (N = 6) or hypoxia (N = 3). A vertical laser line was horizontally scanned on the retina and a series of optical section phase-delayed phosphorescence images were acquired. From these images, phosphorescence volumes at each phase delay were constructed and a 3D retinal tPO2 volume was generated. Retinal tPO2 volumes were quantitatively analyzed by generating retinal depth profiles of mean tPO2 (MtPO2) and the spatial variation of tPO2 (SVtPO2). The effects of systemic condition (normoxia/hypoxia) and retinal depth on MtPO2 and SVtPO2 were determined by mixed linear model. RESULTS Each 3D retinal tPO2 volume was approximately 500 × 750 × 200 μm (horizontal × vertical × depth) and consisted of 45 en face tPO2 images through the retinal depth. MtPO2 at the chorioretinal interface was significantly correlated with systemic arterial oxygen tension (P = 0.007; N = 9). There were significant effects of both systemic condition and retinal depth on MtPO2 and SVtPO2, such that both were lower under hypoxia than normoxia and higher in the outer retina than inner retina (P < 0.001). CONCLUSION For the first time, 3D imaging of retinal tPO2 was demonstrated, with potential future application for assessment of physiological alterations in animal models of retinal diseases.
Collapse
Affiliation(s)
- Anthony E Felder
- a Department of Bioengineering , University of Illinois at Chicago , Chicago IL, USA.,b Department of Ophthalmology and Visual Science , University of Illinois at Chicago , Chicago IL, USA
| | - Justin Wanek
- b Department of Ophthalmology and Visual Science , University of Illinois at Chicago , Chicago IL, USA
| | - Pang-Yu Teng
- b Department of Ophthalmology and Visual Science , University of Illinois at Chicago , Chicago IL, USA
| | - Norman P Blair
- b Department of Ophthalmology and Visual Science , University of Illinois at Chicago , Chicago IL, USA
| | - Mahnaz Shahidi
- c Department of Ophthalmology , University of Southern California , Los Angeles CA, USA
| |
Collapse
|
27
|
A Method for Combined Retinal Vascular and Tissue Oxygen Tension Imaging. Sci Rep 2017; 7:10622. [PMID: 28878307 PMCID: PMC5587610 DOI: 10.1038/s41598-017-10955-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 08/17/2017] [Indexed: 11/17/2022] Open
Abstract
The retina requires adequate oxygenation to maintain cellular metabolism and visual function. Inner retinal oxygen metabolism is directly related to retinal vascular oxygen tension (PO2) and inner retinal oxygen extraction fraction (OEF), whereas outer retinal oxygen consumption (QO2) relies on oxygen availability by the choroid and is contingent upon retinal tissue oxygen tension (tPO2) gradients across the retinal depth. Thus far, these oxygenation and metabolic parameters have been measured independently by different techniques in separate animals, precluding a comprehensive and correlative assessment of retinal oxygenation and metabolism dynamics. The purpose of the current study is to report an innovative optical system for dual oxyphor phosphorescence lifetime imaging to near-simultaneously measure retinal vascular PO2 and tPO2 in rats. The use of a new oxyphor with different spectral characteristics allowed differentiation of phosphorescence signals from the retinal vasculature and tissue. Concurrent measurements of retinal arterial and venous PO2, tPO2 through the retinal depth, inner retinal OEF, and outer retinal QO2 were demonstrated, permitting a correlative assessment of retinal oxygenation and metabolism. Future application of this method can be used to investigate the relations among retinal oxygen content, extraction and metabolism under pathologic conditions and thus advance knowledge of retinal hypoxia pathophysiology.
Collapse
|
28
|
Fondi K, Wozniak PA, Howorka K, Bata AM, Aschinger GC, Popa-Cherecheanu A, Witkowska KJ, Hommer A, Schmidl D, Werkmeister RM, Garhöfer G, Schmetterer L. Retinal oxygen extraction in individuals with type 1 diabetes with no or mild diabetic retinopathy. Diabetologia 2017; 60:1534-1540. [PMID: 28547132 PMCID: PMC5491565 DOI: 10.1007/s00125-017-4309-0] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 04/20/2017] [Indexed: 12/25/2022]
Abstract
AIMS/HYPOTHESIS The aim of this study was to compare retinal oxygen extraction in individuals with diabetes with no or mild non-proliferative diabetic retinopathy and healthy age- and sex-matched volunteers. METHODS A total of 24 participants with type 1 diabetes and 24 healthy age- and sex-matched volunteers were included in this cross-sectional study. Retinal oxygen extraction was measured by combining total retinal blood flow measurements using a custom-built bi-directional Doppler optical coherence tomography system with measurements of oxygen saturation using spectroscopic reflectometry. Based on previously published mathematical modelling, the oxygen content in retinal vessels and total retinal oxygen extraction were calculated. RESULTS Total retinal blood flow was higher in diabetic participants (46.4 ± 7.4 μl/min) than in healthy volunteers (40.4 ± 5.3 μl/min, p = 0.002 between groups). Oxygen content in retinal arteries was comparable between the two groups, but oxygen content in retinal veins was higher in participants with diabetes (0.15 ± 0.02 ml O2/ml) compared with healthy control participants (0.13 ± 0.02 ml O2/ml, p < 0.001). As such, the arteriovenous oxygen difference and total retinal oxygen extraction were reduced in participants with diabetes compared with healthy volunteers (total retinal oxygen extraction 1.40 ± 0.44 vs 1.70 ± 0.47 μl O2/min, respectively, p = 0.03). CONCLUSIONS/INTERPRETATION Our data indicate early retinal hypoxia in individuals with type 1 diabetes with no or mild diabetic retinopathy as compared with healthy control individuals. Further studies are required to fully understand the potential of the technique in risk stratification and treatment monitoring. TRIAL REGISTRATION ClinicalTrials.gov NCT01843114.
Collapse
Affiliation(s)
- Klemens Fondi
- Department of Clinical Pharmacology, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria
| | - Piotr A Wozniak
- Department of Clinical Pharmacology, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria
- Department of Ophthalmology, Medical University of Warsaw, Warsaw, Poland
| | - Kinga Howorka
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
| | - Ahmed M Bata
- Department of Clinical Pharmacology, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria
| | - Gerold C Aschinger
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
| | - Alina Popa-Cherecheanu
- Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
- Department of Ophthalmology, Emergency University Hospital, Bucharest, Romania
| | - Katarzyna J Witkowska
- Department of Clinical Pharmacology, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria
| | - Anton Hommer
- Department of Clinical Pharmacology, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria
- Department of Ophthalmology, Sanatorium Hera, Vienna, Austria
| | - Doreen Schmidl
- Department of Clinical Pharmacology, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria
| | - René M Werkmeister
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
| | - Gerhard Garhöfer
- Department of Clinical Pharmacology, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria
| | - Leopold Schmetterer
- Department of Clinical Pharmacology, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria.
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
- Singapore Eye Research Institute, Singapore, Republic of Singapore.
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Republic of Singapore.
- Imperial College, London, UK.
| |
Collapse
|
29
|
Effect of Rhodopsin Phosphorylation on Dark Adaptation in Mouse Rods. J Neurosci 2017; 36:6973-87. [PMID: 27358455 DOI: 10.1523/jneurosci.3544-15.2016] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 05/17/2016] [Indexed: 12/23/2022] Open
Abstract
UNLABELLED Rhodopsin is a prototypical G-protein-coupled receptor (GPCR) that is activated when its 11-cis-retinal moiety is photoisomerized to all-trans retinal. This step initiates a cascade of reactions by which rods signal changes in light intensity. Like other GPCRs, rhodopsin is deactivated through receptor phosphorylation and arrestin binding. Full recovery of receptor sensitivity is then achieved when rhodopsin is regenerated through a series of steps that return the receptor to its ground state. Here, we show that dephosphorylation of the opsin moiety of rhodopsin is an extremely slow but requisite step in the restoration of the visual pigment to its ground state. We make use of a novel observation: isolated mouse retinae kept in standard media for routine physiologic recordings display blunted dephosphorylation of rhodopsin. Isoelectric focusing followed by Western blot analysis of bleached isolated retinae showed little dephosphorylation of rhodopsin for up to 4 h in darkness, even under conditions when rhodopsin was completely regenerated. Microspectrophotometeric determinations of rhodopsin spectra show that regenerated phospho-rhodopsin has the same molecular photosensitivity as unphosphorylated rhodopsin and that flash responses measured by trans-retinal electroretinogram or single-cell suction electrode recording displayed dark-adapted kinetics. Single quantal responses displayed normal dark-adapted kinetics, but rods were only half as sensitive as those containing exclusively unphosphorylated rhodopsin. We propose a model in which light-exposed retinae contain a mixed population of phosphorylated and unphosphorylated rhodopsin. Moreover, complete dark adaptation can only occur when all rhodopsin has been dephosphorylated, a process that requires >3 h in complete darkness. SIGNIFICANCE STATEMENT G-protein-coupled receptors (GPCRs) constitute the largest superfamily of proteins that compose ∼4% of the mammalian genome whose members share a common membrane topology. Signaling by GPCRs regulate a wide variety of physiological processes, including taste, smell, hearing, vision, and cardiovascular, endocrine, and reproductive homeostasis. An important feature of GPCR signaling is its timely termination. This normally occurs when, after their activation, GPCRs are rapidly phosphorylated by specific receptor kinases and subsequently bound by cognate arrestins. Recovery of receptor sensitivity to the ground state then requires dephosphorylation of the receptor and unbinding of arrestin, processes that are poorly understood. Here we investigate in mouse rod photoreceptors the relationship between rhodopsin dephosphorylation and recovery of visual sensitivity.
Collapse
|
30
|
Narayan DS, Chidlow G, Wood JP, Casson RJ. Glucose metabolism in mammalian photoreceptor inner and outer segments. Clin Exp Ophthalmol 2017; 45:730-741. [PMID: 28334493 DOI: 10.1111/ceo.12952] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 02/25/2017] [Accepted: 03/20/2017] [Indexed: 12/22/2022]
Abstract
Photoreceptors are the first-order neurons of the visual pathway, converting light into electrical signals. Rods and cones are the two main types of photoreceptors in the mammalian retina. Rods are specialized for sensitivity at the expense of resolution and are responsible for vision in dimly lit conditions. Cones are responsible for high acuity central vision and colour vision. Many human retinal diseases are characterized by a progressive loss of photoreceptors. Photoreceptors consist of four primary regions: outer segments, inner segments, cell bodies and synaptic terminals. Photoreceptors consume large amounts of energy, and therefore, energy metabolism may be a critical juncture that links photoreceptor function and survival. Cones require more energy than rods, and cone degeneration is the main cause of clinically significant vision loss in retinal diseases. Photoreceptor segments are capable of utilizing various energy substrates, including glucose, to meet their large energy demands. The pathways by which photoreceptor segments meet their energy demands remain incompletely understood. Improvements in the understanding of glucose metabolism in photoreceptor segments may provide insight into the reasons why photoreceptors degenerate due to energy failure. This may, in turn, assist in developing bio-energetic therapies aimed at protecting photoreceptors.
Collapse
Affiliation(s)
- Daniel S Narayan
- Ophthalmic Research Laboratories, Hanson Institute Centre for Neurological Diseases, Adelaide, South Austalia, Australia.,South Australian Institute of Ophthalmology, University of Adelaide, Adelaide, South Austalia, Australia
| | - Glyn Chidlow
- Ophthalmic Research Laboratories, Hanson Institute Centre for Neurological Diseases, Adelaide, South Austalia, Australia.,South Australian Institute of Ophthalmology, University of Adelaide, Adelaide, South Austalia, Australia
| | - John Pm Wood
- Ophthalmic Research Laboratories, Hanson Institute Centre for Neurological Diseases, Adelaide, South Austalia, Australia.,South Australian Institute of Ophthalmology, University of Adelaide, Adelaide, South Austalia, Australia
| | - Robert J Casson
- Ophthalmic Research Laboratories, Hanson Institute Centre for Neurological Diseases, Adelaide, South Austalia, Australia.,South Australian Institute of Ophthalmology, University of Adelaide, Adelaide, South Austalia, Australia
| |
Collapse
|
31
|
Son T, Wang B, Lu Y, Chen Y, Cao D, Yao X. Concurrent OCT imaging of stimulus evoked retinal neural activation and hemodynamic responses. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2017; 10045. [PMID: 29225397 DOI: 10.1117/12.2252480] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
It is well established that major retinal diseases involve distortions of the retinal neural physiology and blood vascular structures. However, the details of distortions in retinal neurovascular coupling associated with major eye diseases are not well understood. In this study, a multi-modal optical coherence tomography (OCT) imaging system was developed to enable concurrent imaging of retinal neural activity and vascular hemodynamics. Flicker light stimulation was applied to mouse retinas to evoke retinal neural responses and hemodynamic changes. The OCT images were acquired continuously during the pre-stimulation, light-stimulation, and post-stimulation phases. Stimulus-evoked intrinsic optical signals (IOSs) and hemodynamic changes were observed over time in blood-free and blood regions, respectively. Rapid IOSs change occurred almost immediately after stimulation. Both positive and negative signals were observed in adjacent retinal areas. The hemodynamic changes showed time delays after stimulation. The signal magnitudes induced by light stimulation were observed in blood regions and did not show significant changes in blood-free regions. These differences may arise from different mechanisms in blood vessels and neural tissues in response to light stimulation. These characteristics agreed well with our previous observations in mouse retinas. Further development of the multi-modal OCT may provide a new imaging method for studying how retinal structures and metabolic and neural functions are affected by age-related macular degeneration (AMD), glaucoma, diabetic retinopathy (DR), and other diseases, which promises novel noninvasive biomarkers for early disease detection and reliable treatment evaluations of eye diseases.
Collapse
Affiliation(s)
- Taeyoon Son
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Benquan Wang
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Yiming Lu
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Yanjun Chen
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Dingcai Cao
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Xincheng Yao
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA.,Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL 60612, USA
| |
Collapse
|
32
|
Linsenmeier RA, Zhang HF. Retinal oxygen: from animals to humans. Prog Retin Eye Res 2017; 58:115-151. [PMID: 28109737 DOI: 10.1016/j.preteyeres.2017.01.003] [Citation(s) in RCA: 143] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 01/13/2017] [Accepted: 01/17/2017] [Indexed: 10/20/2022]
Abstract
This article discusses retinal oxygenation and retinal metabolism by focusing on measurements made with two of the principal methods used to study O2 in the retina: measurements of PO2 with oxygen-sensitive microelectrodes in vivo in animals with a retinal circulation similar to that of humans, and oximetry, which can be used non-invasively in both animals and humans to measure O2 concentration in retinal vessels. Microelectrodes uniquely have high spatial resolution, allowing the mapping of PO2 in detail, and when combined with mathematical models of diffusion and consumption, they provide information about retinal metabolism. Mathematical models, grounded in experiments, can also be used to simulate situations that are not amenable to experimental study. New methods of oximetry, particularly photoacoustic ophthalmoscopy and visible light optical coherence tomography, provide depth-resolved methods that can separate signals from blood vessels and surrounding tissues, and can be combined with blood flow measures to determine metabolic rate. We discuss the effects on retinal oxygenation of illumination, hypoxia and hyperoxia, and describe retinal oxygenation in diabetes, retinal detachment, arterial occlusion, and macular degeneration. We explain how the metabolic measurements obtained from microelectrodes and imaging are different, and how they need to be brought together in the future. Finally, we argue for revisiting the clinical use of hyperoxia in ophthalmology, particularly in retinal arterial occlusions and retinal detachment, based on animal research and diffusion theory.
Collapse
Affiliation(s)
- Robert A Linsenmeier
- Biomedical Engineering Department, Northwestern University, 2145 Sheridan Road, Evanston 60208-3107, IL, USA; Neurobiology Department, Northwestern University, 2205 Tech Drive, Evanston 60208-3520, IL, USA; Ophthalmology Department, Northwestern University, 645 N. Michigan Ave, Suite 440, Chicago 60611, IL, USA.
| | - Hao F Zhang
- Biomedical Engineering Department, Northwestern University, 2145 Sheridan Road, Evanston 60208-3107, IL, USA; Ophthalmology Department, Northwestern University, 645 N. Michigan Ave, Suite 440, Chicago 60611, IL, USA.
| |
Collapse
|
33
|
Hansen RM, Moskowitz A, Akula JD, Fulton AB. The neural retina in retinopathy of prematurity. Prog Retin Eye Res 2017; 56:32-57. [PMID: 27671171 PMCID: PMC5237602 DOI: 10.1016/j.preteyeres.2016.09.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 09/15/2016] [Accepted: 09/20/2016] [Indexed: 12/26/2022]
Abstract
Retinopathy of prematurity (ROP) is a neurovascular disease that affects prematurely born infants and is known to have significant long term effects on vision. We conducted the studies described herein not only to learn more about vision but also about the pathogenesis of ROP. The coincidence of ROP onset and rapid developmental elongation of the rod photoreceptor outer segments motivated us to consider the role of the rods in this disease. We used noninvasive electroretinographic (ERG), psychophysical, and retinal imaging procedures to study the function and structure of the neurosensory retina. Rod photoreceptor and post-receptor responses are significantly altered years after the preterm days during which ROP is an active disease. The alterations include persistent rod dysfunction, and evidence of compensatory remodeling of the post-receptor retina is found in ERG responses to full-field stimuli and in psychophysical thresholds that probe small retinal regions. In the central retina, both Mild and Severe ROP delay maturation of parafoveal scotopic thresholds and are associated with attenuation of cone mediated multifocal ERG responses, significant thickening of post-receptor retinal laminae, and dysmorphic cone photoreceptors. These results have implications for vision and control of eye growth and refractive development and suggest future research directions. These results also lead to a proposal for noninvasive management using light that may add to the currently invasive therapeutic armamentarium against ROP.
Collapse
Affiliation(s)
- Ronald M Hansen
- Department of Ophthalmology, Children's Hospital and Harvard Medical School, 300 Longwood Ave., Boston, MA 02115-5737, USA.
| | - Anne Moskowitz
- Department of Ophthalmology, Children's Hospital and Harvard Medical School, 300 Longwood Ave., Boston, MA 02115-5737, USA.
| | - James D Akula
- Department of Ophthalmology, Children's Hospital and Harvard Medical School, 300 Longwood Ave., Boston, MA 02115-5737, USA.
| | - Anne B Fulton
- Department of Ophthalmology, Children's Hospital and Harvard Medical School, 300 Longwood Ave., Boston, MA 02115-5737, USA.
| |
Collapse
|
34
|
Uddin MI, Evans SM, Craft JR, Capozzi ME, McCollum GW, Yang R, Marnett LJ, Uddin MJ, Jayagopal A, Penn JS. In Vivo Imaging of Retinal Hypoxia in a Model of Oxygen-Induced Retinopathy. Sci Rep 2016; 6:31011. [PMID: 27491345 PMCID: PMC4974503 DOI: 10.1038/srep31011] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 07/11/2016] [Indexed: 01/16/2023] Open
Abstract
Ischemia-induced hypoxia elicits retinal neovascularization and is a major component of several blinding retinopathies such as retinopathy of prematurity (ROP), diabetic retinopathy (DR) and retinal vein occlusion (RVO). Currently, noninvasive imaging techniques capable of detecting and monitoring retinal hypoxia in living systems do not exist. Such techniques would greatly clarify the role of hypoxia in experimental and human retinal neovascular pathogenesis. In this study, we developed and characterized HYPOX-4, a fluorescence-imaging probe capable of detecting retinal-hypoxia in living animals. HYPOX-4 dependent in vivo and ex vivo imaging of hypoxia was tested in a mouse model of oxygen-induced retinopathy (OIR). Predicted patterns of retinal hypoxia were imaged by HYPOX-4 dependent fluorescence activity in this animal model. In retinal cells and mouse retinal tissue, pimonidazole-adduct immunostaining confirmed the hypoxia selectivity of HYPOX-4. HYPOX-4 had no effect on retinal cell proliferation as indicated by BrdU assay and exhibited no acute toxicity in retinal tissue as indicated by TUNEL assay and electroretinography (ERG) analysis. Therefore, HYPOX-4 could potentially serve as the basis for in vivo fluorescence-based hypoxia-imaging techniques, providing a tool for investigators to understand the pathogenesis of ischemic retinopathies and for physicians to address unmet clinical needs.
Collapse
Affiliation(s)
- Md. Imam Uddin
- Department of Ophthalmology and Visual Sciences, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Stephanie M. Evans
- Department of Ophthalmology and Visual Sciences, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Jason R. Craft
- Department of Ophthalmology and Visual Sciences, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Megan E. Capozzi
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Gary W. McCollum
- Department of Ophthalmology and Visual Sciences, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Rong Yang
- Department of Ophthalmology and Visual Sciences, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Lawrence J. Marnett
- A. B. Hancock, Jr., Memorial Laboratory for Cancer Research, Departments of Biochemistry, Chemistry and Pharmacology, Vanderbilt Institute of Chemical Biology, Center for Molecular Toxicology and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Md. Jashim Uddin
- A. B. Hancock, Jr., Memorial Laboratory for Cancer Research, Departments of Biochemistry, Chemistry and Pharmacology, Vanderbilt Institute of Chemical Biology, Center for Molecular Toxicology and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Ashwath Jayagopal
- Pharma Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche, Ltd., Basel, Switzerland
| | - John S. Penn
- Department of Ophthalmology and Visual Sciences, Vanderbilt University School of Medicine, Nashville, TN, USA
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, USA
| |
Collapse
|
35
|
Son T, Wang B, Thapa D, Lu Y, Chen Y, Cao D, Yao X. Optical coherence tomography angiography of stimulus evoked hemodynamic responses in individual retinal layers. BIOMEDICAL OPTICS EXPRESS 2016; 7:3151-62. [PMID: 27570706 PMCID: PMC4986822 DOI: 10.1364/boe.7.003151] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 06/08/2016] [Accepted: 06/10/2016] [Indexed: 05/05/2023]
Abstract
Blood flow changes are highly related to neural activities in the retina. It has been reported that neural activity increases when flickering light stimulation of the retina is used. It is known that blood flow changes with flickering light stimulation can be altered in patients with vascular disease and that measurement of flicker-induced vasodilatation is an easily applied tool for monitoring functional microvascular alterations. However, details of distortions in retinal neurovascular coupling associated with major eye diseases are not well understood due to the limitation of existing techniques. In this study, flickering light stimulation was applied to mouse retinas to investigate stimulus evoked hemodynamic responses in individual retinal layers. A spectral domain optical coherence tomography (OCT) angiography imaging system was developed to provide dynamic mapping of hemodynamic responses in the ganglion cell layer, inner plexiform layer, outer plexiform layer and choroid layer before, during and after flickering light stimulation. Experimental results showed hemodynamic responses with different magnitudes and time courses in individual retinal layers. We anticipate that the dynamic OCT angiography of stimulus evoked hemodynamic responses can greatly foster the study of neurovascular coupling mechanisms in the retina, promising new biomarkers for retinal disease detection and diagnosis.
Collapse
Affiliation(s)
- Taeyoon Son
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Benquan Wang
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Damber Thapa
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Yiming Lu
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Yanjun Chen
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Dingcai Cao
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Xincheng Yao
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL 60612, USA
| |
Collapse
|
36
|
Rueda EM, Johnson JE, Giddabasappa A, Swaroop A, Brooks MJ, Sigel I, Chaney SY, Fox DA. The cellular and compartmental profile of mouse retinal glycolysis, tricarboxylic acid cycle, oxidative phosphorylation, and ~P transferring kinases. Mol Vis 2016; 22:847-85. [PMID: 27499608 PMCID: PMC4961465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2016] [Accepted: 07/21/2016] [Indexed: 10/26/2022] Open
Abstract
PURPOSE The homeostatic regulation of cellular ATP is achieved by the coordinated activity of ATP utilization, synthesis, and buffering. Glucose is the major substrate for ATP synthesis through glycolysis and oxidative phosphorylation (OXPHOS), whereas intermediary metabolism through the tricarboxylic acid (TCA) cycle utilizes non-glucose-derived monocarboxylates, amino acids, and alpha ketoacids to support mitochondrial ATP and GTP synthesis. Cellular ATP is buffered by specialized equilibrium-driven high-energy phosphate (~P) transferring kinases. Our goals were twofold: 1) to characterize the gene expression, protein expression, and activity of key synthesizing and regulating enzymes of energy metabolism in the whole mouse retina, retinal compartments, and/or cells and 2) to provide an integrative analysis of the results related to function. METHODS mRNA expression data of energy-related genes were extracted from our whole retinal Affymetrix microarray data. Fixed-frozen retinas from adult C57BL/6N mice were used for immunohistochemistry, laser scanning confocal microscopy, and enzymatic histochemistry. The immunoreactivity levels of well-characterized antibodies, for all major retinal cells and their compartments, were obtained using our established semiquantitative confocal and imaging techniques. Quantitative cytochrome oxidase (COX) and lactate dehydrogenase (LDH) activity was determined histochemically. RESULTS The Affymetrix data revealed varied gene expression patterns of the ATP synthesizing and regulating enzymes found in the muscle, liver, and brain. Confocal studies showed differential cellular and compartmental distribution of isozymes involved in glucose, glutamate, glutamine, lactate, and creatine metabolism. The pattern and intensity of the antibodies and of the COX and LDH activity showed the high capacity of photoreceptors for aerobic glycolysis and OXPHOS. Competition assays with pyruvate revealed that LDH-5 was localized in the photoreceptor inner segments. The combined results indicate that glycolysis is regulated by the compartmental expression of hexokinase 2, pyruvate kinase M1, and pyruvate kinase M2 in photoreceptors, whereas the inner retinal neurons exhibit a lower capacity for glycolysis and aerobic glycolysis. Expression of nucleoside diphosphate kinase, mitochondria-associated adenylate kinase, and several mitochondria-associated creatine kinase isozymes was highest in the outer retina, whereas expression of cytosolic adenylate kinase and brain creatine kinase was higher in the cones, horizontal cells, and amacrine cells indicating the diversity of ATP-buffering strategies among retinal neurons. Based on the antibody intensities and the COX and LDH activity, Müller glial cells (MGCs) had the lowest capacity for glycolysis, aerobic glycolysis, and OXPHOS. However, they showed high expression of glutamate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate thiokinase, GABA transaminase, and ~P transferring kinases. This suggests that MGCs utilize TCA cycle anaplerosis and cataplerosis to generate GTP and ~P transferring kinases to produce ATP that supports MGC energy requirements. CONCLUSIONS Our comprehensive and integrated results reveal that the adult mouse retina expresses numerous isoforms of ATP synthesizing, regulating, and buffering genes; expresses differential cellular and compartmental levels of glycolytic, OXPHOS, TCA cycle, and ~P transferring kinase proteins; and exhibits differential layer-by-layer LDH and COX activity. New insights into cell-specific and compartmental ATP and GTP production, as well as utilization and buffering strategies and their relationship with known retinal and cellular functions, are discussed. Developing therapeutic strategies for neuroprotection and treating retinal deficits and degeneration in a cell-specific manner will require such knowledge. This work provides a platform for future research directed at identifying the molecular targets and proteins that regulate these processes.
Collapse
Affiliation(s)
- Elda M. Rueda
- College of Optometry, University of Houston, Houston TX
| | - Jerry E. Johnson
- Department of Natural Sciences, University of Houston-Downtown, Houston TX
- Department of Biology and Biochemistry, University of Houston, Houston TX
| | - Anand Giddabasappa
- Department of Biology and Biochemistry, University of Houston, Houston TX
| | | | | | - Irena Sigel
- College of Optometry, University of Houston, Houston TX
| | - Shawnta Y. Chaney
- Department of Biology and Biochemistry, University of Houston, Houston TX
| | - Donald A. Fox
- College of Optometry, University of Houston, Houston TX
- Department of Biology and Biochemistry, University of Houston, Houston TX
- Department of Pharmacology and Pharmaceutical Sciences, University of Houston, Houston TX
| |
Collapse
|
37
|
Dmitriev AV, Henderson D, Linsenmeier RA. Development of diabetes-induced acidosis in the rat retina. Exp Eye Res 2016; 149:16-25. [PMID: 27262608 DOI: 10.1016/j.exer.2016.05.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 05/18/2016] [Accepted: 05/31/2016] [Indexed: 02/02/2023]
Abstract
We hypothesized that the retina of diabetic animals would be unusually acidic due to increased glycolytic metabolism. Acidosis in tumors and isolated retina has been shown to lead to increased VEGF. To test the hypothesis we have measured the transretinal distribution of extracellular H(+) concentration (H(+)-profiles) in retinae of control and diabetic dark-adapted intact Long-Evans rats with ion-selective electrodes. Diabetes was induced by intraperitoneal injection of streptozotocin. Intact rat retinae are normally more acidic than blood with a peak of [H(+)]o in the outer nuclear layer (ONL) that averages 30 nM higher than H(+) in the choroid. Profiles in diabetic animals were similar in shape, but diabetic retinae began to be considerably more acidic after 5 weeks of diabetes. In retinae of 1-3 month diabetics the difference between the ONL and choroid was almost twice as great as in controls. At later times, up to 6 months, some diabetics still demonstrated abnormally high levels of [H(+)]o, but others were even less acidic than controls, so that the average level of acidosis was not different. Greater variability in H(+)-profiles (both between animals and between profiles recorded in one animal) distinguished the diabetic retinae from controls. Within animals, this variability was not random, but exhibited regions of higher and lower H(+). We conclude that retinal acidosis begins to develop at an early stage of diabetes (1-3 months) in rats. However, it does not progress, and the acidity of diabetic rat retina was diminished at later stages (3-6 months). Also the diabetes-induced acidosis has a strongly expressed local character. As result, the diabetic retinas show much wider variability in [H(+)] distribution than controls. pH influences metabolic and neural processes, and these results suggest that local acidosis could play a role in the pathogenesis of diabetic retinopathy.
Collapse
Affiliation(s)
- Andrey V Dmitriev
- Department of Biomedical Engineering, 2145 Sheridan Road, Northwestern University, Evanston, IL 60208-3107, United States.
| | - Desmond Henderson
- Department of Biomedical Engineering, 2145 Sheridan Road, Northwestern University, Evanston, IL 60208-3107, United States.
| | - Robert A Linsenmeier
- Department of Biomedical Engineering, 2145 Sheridan Road, Northwestern University, Evanston, IL 60208-3107, United States; Department of Neurobiology, 2205 Tech Drive, Northwestern University, Evanston, IL 60208, United States; Department of Ophthalmology, Northwestern University, 645 North Michigan Avenue, Suite 440, Chicago, IL 60611, United States.
| |
Collapse
|
38
|
Dmitriev AV, Henderson D, Linsenmeier RA. Light-induced pH changes in the intact retinae of normal and early diabetic rats. Exp Eye Res 2016; 145:148-157. [PMID: 26639389 PMCID: PMC4842083 DOI: 10.1016/j.exer.2015.11.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 11/22/2015] [Accepted: 11/23/2015] [Indexed: 12/26/2022]
Abstract
Double-barreled H(+)-selective microelectrodes were used to measure local extracellular concentration of H(+) ([H(+)]o) in the retina of dark-adapted anesthetized Long-Evans rats. The microelectrode advanced in steps of 30 μm throughout the retina from the vitreal surface to retinal pigment epithelium and then to the choroid, recording changes in [H(+)]o evoked by light stimulation. Recordings were performed in diabetic rats 1-3 months after intraperitoneal injection of streptozotocin and the results were compared with data obtained in age-matched control animals. Brief light stimulation (2.5 s) evoked changes of [H(+)]o with amplitudes of a few nM. Throughout the retina, there was a transient initial acidification for ∼200 ms followed by steady alkalinization, although amplitudes and kinetics of these components were slightly variable in different retinal layers. No significant difference was found when the light-induced [H(+)]o changes recorded in various retinal layers of early diabetic rats were compared with the [H(+)]o changes from corresponding layers of control animals. Also, when H(+)-selective microelectrodes were located in the retinal pigment epithelium (RPE) layer, an increase in H(+) was recorded, whose time course and amplitude were similar in control and diabetic rats. However, a striking difference between light-induced [H(+)]o changes in controls and diabetics was observed in the choriocapillaris, in the thin layer (10-20 μm) distal to the basal membrane of the RPE. In control rats, choroidal [H(+)]o decreased in a few cases, but much more often practically did not change. In contrast, diabetic rats demonstrated either an increase (in half of the cases) or no change in choroidal [H(+)]o. The data suggest that the active participation of the choroidal blood supply in stabilization of [H(+)]o could be partially compromised already at early stages of diabetes in rats. Interestingly, it appeared that the acid removal by the choroidal circulation was compromised most after 1 month of diabetes and tended to improve later.
Collapse
Affiliation(s)
- Andrey V Dmitriev
- Department of Biomedical Engineering, 2145 Sheridan Road, Northwestern University, Evanston, IL 60208-3107, United States.
| | - Desmond Henderson
- Department of Biomedical Engineering, 2145 Sheridan Road, Northwestern University, Evanston, IL 60208-3107, United States.
| | - Robert A Linsenmeier
- Department of Biomedical Engineering, 2145 Sheridan Road, Northwestern University, Evanston, IL 60208-3107, United States; Department of Neurobiology, 2205 Tech Drive, Northwestern University, Evanston, IL 60208, United States; Department of Ophthalmology, Northwestern University, 645 North Michigan Avenue, Suite 440, Chicago, IL 60611, United States.
| |
Collapse
|
39
|
Sivaprasad S, Arden G. Spare the rods and spoil the retina: revisited. Eye (Lond) 2016; 30:189-92. [PMID: 26656085 PMCID: PMC4763134 DOI: 10.1038/eye.2015.254] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 11/10/2015] [Indexed: 01/23/2023] Open
Abstract
Visual function improves with oxygen inhalation in people with diabetes even in the absence of visible retinopathy. Rods consume the most oxygen in the retina due to the high metabolic activity required to maintain the dark current. Therefore, Arden hypothesized that in diabetes where oxygen supply may also be affected due to the changes in retinal vasculature, prevention of dark adaptation may be a viable option to prevent or decrease the rate of progression of diabetic retinopathy. Animal experiments have proven that the absence of rods decreases the development of retinal neovascularisation. The same principle applies to panretinal photocoagulation, an established treatment for proliferative diabetic retinopathy. Recently, a few clinical studies have also shown that preventing dark adaptation by suppressing rods with 500-nm light source at night decreases the rate of progression of early diabetic retinopathy and maculopathy in the short-term. We await the results of a large two-year multi-centre trial (CLEOPATRA trial) to evaluate the long-term effects of decreasing dark adaptation by applying a 500nm light source as a mask over eyes with non-central diabetic macular oedema.
Collapse
Affiliation(s)
- S Sivaprasad
- NIHR Moorfields Biomedical Research Centre, London, UK
| | - G Arden
- NIHR Moorfields Biomedical Research Centre, London, UK
| |
Collapse
|
40
|
Du J, Rountree A, Cleghorn WM, Contreras L, Lindsay KJ, Sadilek M, Gu H, Djukovic D, Raftery D, Satrústegui J, Kanow M, Chan L, Tsang SH, Sweet IR, Hurley JB. Phototransduction Influences Metabolic Flux and Nucleotide Metabolism in Mouse Retina. J Biol Chem 2015; 291:4698-710. [PMID: 26677218 DOI: 10.1074/jbc.m115.698985] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Indexed: 01/20/2023] Open
Abstract
Production of energy in a cell must keep pace with demand. Photoreceptors use ATP to maintain ion gradients in darkness, whereas in light they use it to support phototransduction. Matching production with consumption can be accomplished by coupling production directly to consumption. Alternatively, production can be set by a signal that anticipates demand. In this report we investigate the hypothesis that signaling through phototransduction controls production of energy in mouse retinas. We found that respiration in mouse retinas is not coupled tightly to ATP consumption. By analyzing metabolic flux in mouse retinas, we also found that phototransduction slows metabolic flux through glycolysis and through intermediates of the citric acid cycle. We also evaluated the relative contributions of regulation of the activities of α-ketoglutarate dehydrogenase and the aspartate-glutamate carrier 1. In addition, a comprehensive analysis of the retinal metabolome showed that phototransduction also influences steady-state concentrations of 5'-GMP, ribose-5-phosphate, ketone bodies, and purines.
Collapse
Affiliation(s)
- Jianhai Du
- From the Department of Biochemistry, Department of Ophthalmology, University of Washington, Seattle, Washington 98109
| | | | | | - Laura Contreras
- Department of Molecular Biology, Centre for Molecular Biology Severo Ochoa, Universidad Autonoma de Madrid-Consejo Superior de Investigaciones Científicas, CIBER of Rare Diseases (CIBERER), and Health Research Institute Jimenez Diaz Foundation, Autonomous University of Madrid, 28049 Madrid, Spain
| | | | | | - Haiwei Gu
- Northwest Metabolomics Research Center, Department of Anesthesiology and Pain Medicine
| | - Danijel Djukovic
- Northwest Metabolomics Research Center, Department of Anesthesiology and Pain Medicine
| | - Dan Raftery
- Northwest Metabolomics Research Center, Department of Anesthesiology and Pain Medicine
| | - Jorgina Satrústegui
- Department of Molecular Biology, Centre for Molecular Biology Severo Ochoa, Universidad Autonoma de Madrid-Consejo Superior de Investigaciones Científicas, CIBER of Rare Diseases (CIBERER), and Health Research Institute Jimenez Diaz Foundation, Autonomous University of Madrid, 28049 Madrid, Spain
| | | | - Lawrence Chan
- Bernard and Shirlee Brown Glaucoma Laboratory and Barbara and Donald Jonas Stem Cell Laboratory, Department of Ophthalmology, Columbia University, New York, New York, and
| | - Stephen H Tsang
- Bernard and Shirlee Brown Glaucoma Laboratory and Barbara and Donald Jonas Stem Cell Laboratory, Department of Ophthalmology, Columbia University, New York, New York, and Department of Pathology and Cell Biology and Institute of Human Nutrition, Columbia University, New York, New York 10032
| | | | - James B Hurley
- From the Department of Biochemistry, Department of Ophthalmology, University of Washington, Seattle, Washington 98109,
| |
Collapse
|
41
|
Yang F, Yang CH, Wang FM, Cheng YT, Teng CC, Lee LJ, Yang CH, Fan LS. A high-density microelectrode-tissue-microelectrode sandwich platform for application of retinal circuit study. Biomed Eng Online 2015; 14:109. [PMID: 26611649 PMCID: PMC4662037 DOI: 10.1186/s12938-015-0106-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 11/23/2015] [Indexed: 01/05/2023] Open
Abstract
Background Microelectrode array (MEA) devices are frequently used in neural circuit studies, especially in retinal prosthesis. For a high throughput stimulation and recording paradigm, it is desirable to obtain the responses of multiple surface RGCs initiated from the electrical signals delivered to multiple photoreceptor cells. This can be achieved by an high density MEA-tissue-MEA (MTM) sandwich configuration. However, the retina is one of the most metabolically active tissues, consumes oxygen as rapidly as the brain. The major concern of the MTM configuration is the supply of oxygen. Methods We aimed to develop a high density MTM sandwich platform which consists of stacks of a stimulation MEA, retinal tissue and a recording MEA. Retina is a metabolically active tissue and the firing rate is very sensitive to oxygen level. We designed, simulated and microfabricated porous high density MEAs and an adjustable perfusion system that electrical signals can be delivered to and recorded from the clipped retinal tissue. Results The porous high-density MEAs linked with stimulation or recording devices within a perfusion system were manufactured and the MTM platform was assembled with a retina slice inside. The firing rate remained constant between 25 and 55 min before dramatically declined, indicating that within certain period of time (e.g. 30 min after habituation), the retina condition was kept by sufficient oxygen supply via the perfusion holes in the MEAs provided by the double perfusion system. Conclusions MTM sandwich structure is an efficient platform to study the retinal neural circuit. The material and arrangement of high density microelectrodes with porous design make this MEA appropriate for sub-retina prosthesis. Finding ways to prolong the recording time and reduce the signal-to-noise ratio are important to improve our MTM prototype.
Collapse
Affiliation(s)
- Frank Yang
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan
| | - Chung-Hua Yang
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan
| | - Fu-Min Wang
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan
| | - Ya-Ting Cheng
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan
| | - Chih-Ciao Teng
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan
| | - Li-Jen Lee
- Graduated Institute of Anatomy and Cell Biology, National Taiwan University, Taipei, Taiwan
| | - Chang-Hao Yang
- Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan
| | - Long-Sheng Fan
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsin-Chu, Taiwan.
| |
Collapse
|
42
|
Yi J, Liu W, Chen S, Backman V, Sheibani N, Sorenson CM, Fawzi AA, Linsenmeier RA, Zhang HF. Visible light optical coherence tomography measures retinal oxygen metabolic response to systemic oxygenation. LIGHT, SCIENCE & APPLICATIONS 2015; 4:e334. [PMID: 26658555 PMCID: PMC4674267 DOI: 10.1038/lsa.2015.107] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The lack of capability to quantify oxygen metabolism noninvasively impedes both fundamental investigation and clinical diagnosis of a wide spectrum of diseases including all the major blinding diseases such as age-related macular degeneration, diabetic retinopathy, and glaucoma. Using visible light optical coherence tomography (vis-OCT), we demonstrated accurate and robust measurement of retinal oxygen metabolic rate (rMRO2) noninvasively in rat eyes. We continuously monitored the regulatory response of oxygen consumption to a progressive hypoxic challenge. We found that both oxygen delivery, and rMRO2 increased from the highly regulated retinal circulation (RC) under hypoxia, by 0.28 ± 0.08 μL min-1 (p < 0.001), and 0.20 ± 0.04 μL min-1 (p < 0.001) per 100 mmHg systemic pO2 reduction, respectively. The increased oxygen extraction compensated for the deficient oxygen supply from the poorly regulated choroidal circulation. Results from an oxygen diffusion model based on previous oxygen electrode measurements corroborated our in vivo observations. We believe that vis-OCT has the potential to reveal the fundamental role of oxygen metabolism in various retinal diseases.
Collapse
Affiliation(s)
- Ji Yi
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Wenzhong Liu
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Siyu Chen
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Vadim Backman
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Nader Sheibani
- McPherson Eye Research Institute, University of Wisconsin, Madison, WI 53705, USA
| | - Christine M Sorenson
- McPherson Eye Research Institute, University of Wisconsin, Madison, WI 53705, USA
| | - Amani A Fawzi
- Department of Ophthalmology, Northwestern University, Chicago Illinois 60611, USA
| | - Robert A Linsenmeier
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA ; Department of Ophthalmology, Northwestern University, Chicago Illinois 60611, USA ; Department of Neurobiology, Northwestern University, Evanston, IL 60208, USA
| | - Hao F Zhang
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA ; Department of Ophthalmology, Northwestern University, Chicago Illinois 60611, USA
| |
Collapse
|
43
|
Lin MK, Kim SH, Zhang L, Tsai YT, Tsang SH. Rod metabolic demand drives progression in retinopathies. Taiwan J Ophthalmol 2015; 5:105-108. [PMID: 29018679 PMCID: PMC5602704 DOI: 10.1016/j.tjo.2015.06.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2015] [Accepted: 06/30/2015] [Indexed: 12/21/2022] Open
Abstract
Various factors are thought to cause the development and progression of disease in macular degeneration, diabetic retinopathy, and retinitis pigmentosa. Some of the deleterious processes include oxidative stress, hypoxia, metabolic derangement, genetics, and vasculopathy. In this review, we present a unified theory for the pathophysiology of several retinopathies based on the unique and intense metabolism of rod photoreceptors.
Collapse
Affiliation(s)
- Michael K Lin
- College of Physicians & Surgeons, Columbia University, New York, NY, USA
| | - Soo Hyun Kim
- Columbia College, Columbia University, New York, NY, USA
| | - Lijuan Zhang
- Bernard & Shirlee Brown Glaucoma Laboratory and Barbara & Donald Jonas Stem Cell Laboratory, Department of Ophthalmology, Columbia University, New York, NY, USA
| | - Yi-Ting Tsai
- Bernard & Shirlee Brown Glaucoma Laboratory and Barbara & Donald Jonas Stem Cell Laboratory, Department of Ophthalmology, Columbia University, New York, NY, USA
| | - Stephen H Tsang
- Bernard & Shirlee Brown Glaucoma Laboratory and Barbara & Donald Jonas Stem Cell Laboratory, Department of Ophthalmology, Columbia University, New York, NY, USA.,Department of Pathology and Cell Biology and Institute of Human Nutrition, Columbia University, New York, NY, USA
| |
Collapse
|
44
|
Whitmore SS, Sohn EH, Chirco KR, Drack AV, Stone EM, Tucker BA, Mullins RF. Complement activation and choriocapillaris loss in early AMD: implications for pathophysiology and therapy. Prog Retin Eye Res 2015; 45:1-29. [PMID: 25486088 PMCID: PMC4339497 DOI: 10.1016/j.preteyeres.2014.11.005] [Citation(s) in RCA: 159] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Revised: 11/19/2014] [Accepted: 11/25/2014] [Indexed: 12/24/2022]
Abstract
Age-related macular degeneration (AMD) is a common and devastating disease that can result in severe visual dysfunction. Over the last decade, great progress has been made in identifying genetic variants that contribute to AMD, many of which lie in genes involved in the complement cascade. In this review we discuss the significance of complement activation in AMD, particularly with respect to the formation of the membrane attack complex in the aging choriocapillaris. We review the clinical, histological and biochemical data that indicate that vascular loss in the choroid occurs very early in the pathogenesis of AMD, and discuss the potential impact of vascular dropout on the retinal pigment epithelium, Bruch's membrane and the photoreceptor cells. Finally, we present a hypothesis for the pathogenesis of early AMD and consider the implications of this model on the development of new therapies.
Collapse
Affiliation(s)
- S Scott Whitmore
- The Stephen A. Wynn Institute for Vision Research, The University of Iowa, United States; Department of Ophthalmology and Visual Sciences, The University of Iowa, United States
| | - Elliott H Sohn
- The Stephen A. Wynn Institute for Vision Research, The University of Iowa, United States; Department of Ophthalmology and Visual Sciences, The University of Iowa, United States
| | - Kathleen R Chirco
- The Stephen A. Wynn Institute for Vision Research, The University of Iowa, United States; Department of Ophthalmology and Visual Sciences, The University of Iowa, United States
| | - Arlene V Drack
- The Stephen A. Wynn Institute for Vision Research, The University of Iowa, United States; Department of Ophthalmology and Visual Sciences, The University of Iowa, United States
| | - Edwin M Stone
- The Stephen A. Wynn Institute for Vision Research, The University of Iowa, United States; Department of Ophthalmology and Visual Sciences, The University of Iowa, United States
| | - Budd A Tucker
- The Stephen A. Wynn Institute for Vision Research, The University of Iowa, United States; Department of Ophthalmology and Visual Sciences, The University of Iowa, United States
| | - Robert F Mullins
- The Stephen A. Wynn Institute for Vision Research, The University of Iowa, United States; Department of Ophthalmology and Visual Sciences, The University of Iowa, United States
| |
Collapse
|
45
|
Abstract
Light stimulation evokes neuronal activity in the retina, resulting in the dilation of retinal blood vessels and increased blood flow. This response, named functional hyperemia, brings oxygen and nutrients to active neurons. However, it remains unclear which vessels mediate functional hyperemia. We have characterized blood flow regulation in the rat retina in vivo by measuring changes in retinal vessel diameter and red blood cell (RBC) flux evoked by a flickering light stimulus. We found that, in first- and second-order arterioles, flicker evoked large (7.5 and 5.0%), rapid (0.73 and 0.70 s), and consistent dilations. Flicker-evoked dilations in capillaries were smaller (2.0%) and tended to have a slower onset (0.97 s), whereas dilations in venules were smaller (1.0%) and slower (1.06 s) still. The proximity of pericyte somata did not predict capillary dilation amplitude. Expression of the contractile protein α-smooth muscle actin was high in arterioles and low in capillaries. Unexpectedly, we found that blood flow in the three vascular layers was differentially regulated. Flicker stimulation evoked far larger dilations and RBC flux increases in the intermediate layer capillaries than in the superficial and deep layer capillaries (2.6 vs 0.9 and 0.7% dilation; 25.7 vs 0.8 and 11.3% RBC flux increase). These results indicate that functional hyperemia in the retina is driven primarily by active dilation of arterioles. The dilation of intermediate layer capillaries is likely mediated by active mechanisms as well. The physiological consequences of differential regulation in the three vascular layers are discussed.
Collapse
|
46
|
Abstract
In diabetic retinopathy, neovascularization is hypothesized to develop due to hypoxia in the retina. However, evidence for retinal hypoxia is limited, and the progressive changes in oxygenation are unknown. The objective of this study was to determine if retinal hypoxia occurs early in the development of diabetes. Intraretinal oxygen (PO2) profiles were recorded with oxygen-sensitive microelectrodes in control and diabetic Long-Evans rats at 4 and 12 weeks after induction of diabetes. Diabetes did not affect oxygen consumption in the photoreceptors in either dark or light adaptation. Oxygenation of the inner retina was not affected after 4 weeks of diabetes, although vascular endothelial growth factor levels increased. At 12 weeks, average inner retinal PO2, normalized to choriocapillaris PO2, was higher in diabetic rats than in age-matched controls, which was opposite to what was expected. Thus retinal hypoxia is not a condition of early diabetes in rat retina. Increased inner retinal PO2 may occur because oxygen consumption decreases in the inner retina.
Collapse
Affiliation(s)
- Jennifer C M Lau
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL
| | - Robert A Linsenmeier
- Department of Biomedical Engineering, Northwestern University, Evanston, IL Department of Neurobiology, Northwestern University, Evanston, IL Department of Ophthalmology, Northwestern University, Chicago, IL
| |
Collapse
|
47
|
Sun N, Ly A, Meding S, Witting M, Hauck SM, Ueffing M, Schmitt-Kopplin P, Aichler M, Walch A. High-resolution metabolite imaging of light and dark treated retina using MALDI-FTICR mass spectrometry. Proteomics 2014; 14:913-23. [PMID: 24459044 DOI: 10.1002/pmic.201300407] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 12/06/2013] [Accepted: 12/20/2013] [Indexed: 11/06/2022]
Abstract
MS imaging (MSI) is a valuable tool for diagnostics and systems biology studies, being a highly sensitive, label-free technique capable of providing comprehensive spatial distribution of different classes of biomolecules. The application of MSI to the study of endogenous compounds has received considerable attention because metabolites are the result of the interactions of a biosystem with its environment. MSI can therefore enhance understanding of disease mechanisms and elucidate mechanisms for biological variation. We present the in situ comparative metabolomics imaging data for analyses of light- and dark-treated retina using MALDI-FTICR. A wide variety of tissue metabolites were imaged at a high spatial resolution. These include nucleotides, central carbon metabolism pathway intermediates, 2-oxocarboxylic acid metabolism, oxidative phosphorylation, glycerophospholipid metabolism, and cysteine and methionine metabolites. The high lateral resolution enabled the differentiation of retinal layers, allowing determination of the spatial distributions of different endogenous compounds. A number of metabolites demonstrated differences between light and dark conditions. These findings add to the understanding of metabolic activity in the retina.
Collapse
Affiliation(s)
- Na Sun
- Research Unit Analytical Pathology, Institute of Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
| | | | | | | | | | | | | | | | | |
Collapse
|
48
|
Song W, Wei Q, Liu W, Liu T, Yi J, Sheibani N, Fawzi AA, Linsenmeier RA, Jiao S, Zhang HF. A combined method to quantify the retinal metabolic rate of oxygen using photoacoustic ophthalmoscopy and optical coherence tomography. Sci Rep 2014; 4:6525. [PMID: 25283870 PMCID: PMC4185377 DOI: 10.1038/srep06525] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Accepted: 09/15/2014] [Indexed: 11/25/2022] Open
Abstract
Quantitatively determining physiological parameters at a microscopic level in the retina furthers the understanding of the molecular pathways of blinding diseases, such as diabetic retinopathy and glaucoma. An essential parameter, which has yet to be quantified noninvasively, is the retinal oxygen metabolic rate (rMRO2). Quantifying rMRO2 is challenging because two parameters, the blood flow rate and hemoglobin oxygen saturation (sO2), must be measured together. We combined photoacoustic ophthalmoscopy (PAOM) with spectral domain-optical coherence tomography (SD-OCT) to tackle this challenge, in which PAOM measured the sO2 and SD-OCT mapped the blood flow rate. We tested the integrated system on normal wild-type rats, in which the measured rMRO2 was 297.86 ± 70.23 nl/minute. This quantitative method may shed new light on both fundamental research and clinical care in ophthalmology in the future.
Collapse
Affiliation(s)
- Wei Song
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
- Department of Physics, Harbin Institute of Technology, 92 West Da-Zhi Street Nangang District, Harbin, Heilongjiang 150080, China
- These authors contributed equally to this work
| | - Qing Wei
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
- These authors contributed equally to this work
| | - Wenzhong Liu
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
- These authors contributed equally to this work
| | - Tan Liu
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Ji Yi
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Nader Sheibani
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, WI 53792, USA
| | - Amani A. Fawzi
- Department of Ophthalmology, Northwestern University, Chicago, IL 60611, USA
| | - Robert A. Linsenmeier
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
- Department of Ophthalmology, Northwestern University, Chicago, IL 60611, USA
- Department of Neurobiology and Physiology, Northwestern University, Evanston, IL 60208, USA
| | - Shuliang Jiao
- Department of Biomedical Engineering, Florida International University, Miami, FL 33174, USA
| | - Hao F. Zhang
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA
- Department of Ophthalmology, Northwestern University, Chicago, IL 60611, USA
| |
Collapse
|
49
|
Teng PY, Wanek J, Blair NP, Shahidi M. Response of inner retinal oxygen extraction fraction to light flicker under normoxia and hypoxia in rat. Invest Ophthalmol Vis Sci 2014; 55:6055-8. [PMID: 25183761 DOI: 10.1167/iovs.13-13811] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Oxygen extraction fraction (OEF), defined by the ratio of oxygen metabolism (MO2) to delivery (DO2), determines the level of compensation of MO2 by DO2. In the current study, we tested the hypothesis that inner retinal OEF remains unchanged during light flicker under systemic normoxia and hypoxia in rats due to the matching of MO2 and DO2. METHODS Retinal vascular oxygen tension (PO2) measurements were obtained in 10 rats by phosphorescence lifetime imaging. Inner retinal OEF was derived from vascular PO2 based on Fick's principle. Measurements were obtained before and during light flicker under systemic normoxia and hypoxia. The effects of light flicker and systemic oxygenation on retinal vascular PO2 and OEF were determined by ANOVA. RESULTS During light flicker, retinal venous PO2 decreased (P < 0.01, N = 10), while inner retinal OEF increased (P = 0.02). Under hypoxia, retinal arterial and venous PO2 decreased (P < 0.01), while OEF increased (P < 0.01). The interaction effect was not significant on OEF (P = 0.52), indicating the responses of OEF to light flicker were similar under normoxia and hypoxia. During light flicker, OEF increased from 0.46 ± 0.13 to 0.50 ± 0.11 under normoxia, while under hypoxia, OEF increased from 0.67 ± 0.16 to 0.74 ± 0.14. CONCLUSIONS Inner retinal OEF increased during light flicker, indicating the relative change in DO2 is less than that in MO2 in rats under systemic normoxia and hypoxia. Inner retinal OEF is a potentially useful parameter for assessment of the relative changes of MO2 and DO2 under physiologic and pathologic conditions.
Collapse
Affiliation(s)
- Pang-yu Teng
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Justin Wanek
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Norman P Blair
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Mahnaz Shahidi
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| |
Collapse
|
50
|
Wanek J, Teng PY, Blair NP, Shahidi M. Inner retinal oxygen delivery and metabolism in streptozotocin diabetic rats. Invest Ophthalmol Vis Sci 2014; 55:1588-93. [PMID: 24550355 DOI: 10.1167/iovs.13-13537] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
PURPOSE The purpose of the study is to report global measurements of inner retinal oxygen delivery (DO2_IR) and oxygen metabolism (MO2_IR) in streptozotocin (STZ) diabetic rats. METHODS Phosphorescence lifetime and blood flow imaging were performed in rats 4 (STZ/4 wk; n = 10) and 6 (STZ/6 wk; n = 10) weeks following injection of STZ to measure retinal arterial (O2A) and venous (O2V) oxygen contents and total retinal blood flow (F). DO2_IR and MO2_IR were calculated from measurements of F and O2A and of F and the arteriovenous oxygen content difference, respectively. Data in STZ rats were compared to those in healthy control rats (n = 10). RESULTS Measurements of O2A and O2V were not significantly different among STZ/4 wk, STZ/6 wk, and control rats (P ≥ 0.28). Likewise, F was similar among all groups of rats (P = 0.81). DO2_IR measurements were 941 ± 231, 956 ± 232, and 973 ± 243 nL O2/min in control, STZ/4 wk, and STZ/6 wk rats, respectively (P = 0.95). MO2_IR measurements were 516 ± 175, 444 ± 103, and 496 ± 84 nL O2/min in control, STZ/4 wk, and STZ/6 wk rats, respectively (P = 0.37). CONCLUSIONS Global inner retinal oxygen delivery and metabolism were not significantly impaired in STZ rats in early diabetes.
Collapse
Affiliation(s)
- Justin Wanek
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois
| | | | | | | |
Collapse
|