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Zhou SW, Zhang Y, Noam N, Rabinovitch D, Bar D, Yousif BS, O'Brien R, Hiya FE, Lin Y, Berni A, Gregori G, Wang RK, Rosenfeld PJ, Trivizki O. The Impact of Carotid Endarterectomy on Choriocapillaris Perfusion. Invest Ophthalmol Vis Sci 2023; 64:42. [PMID: 38153750 PMCID: PMC10756242 DOI: 10.1167/iovs.64.15.42] [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: 05/30/2023] [Accepted: 12/03/2023] [Indexed: 12/29/2023] Open
Abstract
Purpose The impact of carotid endarterectomy (CEA) on choriocapillaris (CC) perfusion was investigated using swept-source optical coherence tomography angiography (SS-OCTA) imaging before and after surgery in patients with clinically significant carotid artery stenosis (CAS). Methods In this prospective observational study, patients with clinically significant CAS undergoing unilateral CEA had SS-OCTA imaging performed in both eyes before and within 1 week after surgery. The percent CC flow deficits (CC FD%) and CC thickness were assessed using previously validated algorithms. Multivariable regression analysis was conducted to evaluate the impact of variables on the change in CC measurements. Results A total of 112 eyes from 56 patients with an average age of 72.6 ± 6.9 years were enrolled. At baseline, significantly higher CC FD% and thinner CC thickness were observed on the surgical side (eyes ipsilateral to the side of CEA) versus the nonsurgical side (eyes contralateral to the side of CEA) (P = 0.001 and P = 0.03, respectively). Following CEA, a significant reduction in CC FD% and a significant increase in CC thickness were detected on the surgical as compared with the nonsurgical side (P = 0.008 and P = 0.01, respectively). Smoking status positively affected CC FD% change (coefficient of variation [CV] = 0.84, P = 0.01) on the surgical side and negatively affected CC thickness change on both the surgical side (CV = -0.382, P = 0.009) and the nonsurgical side (CV = -0.321, P = 0.04). The degree of stenosis demonstrated a positive influence on CC FD% change (CV = 0.040, P = 0.02) on the surgical side. Conclusions Unilateral CEA on the side of clinically significant CAS increases carotid blood flow, which further results in improved CC perfusion.
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Affiliation(s)
- Sandy W. Zhou
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States
- Department of Ophthalmology, Tan Tock Seng Hospital, National Health Group Eye Institute, Singapore
| | - Yi Zhang
- Department of Bioengineering, University of Washington, Seattle, Washington, United States
| | - Natalie Noam
- Department of Vascular Surgery, Tel Aviv Medical Center, University of Tel Aviv, Tel Aviv, Israel
| | - David Rabinovitch
- Department of Ophthalmology, Tel Aviv Medical Center, University of Tel Aviv, Tel Aviv, Israel
| | - Davidov Bar
- Department of Ophthalmology, Tel Aviv Medical Center, University of Tel Aviv, Tel Aviv, Israel
| | - Basheer S. Yousif
- Department of Vascular Surgery, Tel Aviv Medical Center, University of Tel Aviv, Tel Aviv, Israel
| | - Robert O'Brien
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States
| | - Farhan E. Hiya
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States
| | - Yufen Lin
- Department of Bioengineering, University of Washington, Seattle, Washington, United States
| | - Alessandro Berni
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States
| | - Giovanni Gregori
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States
| | - Ruikang K. Wang
- Department of Bioengineering, University of Washington, Seattle, Washington, United States
- Department of Ophthalmology, University of Washington, Seattle, Washington, United States
| | - Philip J. Rosenfeld
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States
| | - Omer Trivizki
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States
- Department of Ophthalmology, Tel Aviv Medical Center, University of Tel Aviv, Tel Aviv, Israel
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Kaur G, Harris NR. Endothelial glycocalyx in retina, hyperglycemia, and diabetic retinopathy. Am J Physiol Cell Physiol 2023; 324:C1061-C1077. [PMID: 36939202 PMCID: PMC10125029 DOI: 10.1152/ajpcell.00188.2022] [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: 05/05/2022] [Revised: 02/28/2023] [Accepted: 03/16/2023] [Indexed: 03/21/2023]
Abstract
The endothelial glycocalyx (EG) is a meshlike network present on the apical surface of the endothelium. Membrane-bound proteoglycans, the major backbone molecules of the EG, consist of glycosaminoglycans attached to core proteins. In addition to maintaining the integrity of the endothelial barrier, the EG regulates inflammation and perfusion and acts as a mechanosensor. The loss of the EG can cause endothelial dysfunction and drive the progression of vascular diseases including diabetic retinopathy. Therefore, the EG presents a novel therapeutic target for treatment of vascular complications. In this review article, we provide an overview of the structure and function of the EG in the retina. Our particular focus is on hyperglycemia-induced perturbations in the glycocalyx structure in the retina, potential underlying mechanisms, and clinical trials studying protective treatments against degradation of the EG.
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Affiliation(s)
- Gaganpreet Kaur
- Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center-Shreveport, Shreveport, Louisiana, United States
| | - Norman R Harris
- Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center-Shreveport, Shreveport, Louisiana, United States
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Böhm EW, Pfeiffer N, Wagner FM, Gericke A. Methods to measure blood flow and vascular reactivity in the retina. Front Med (Lausanne) 2023; 9:1069449. [PMID: 36714119 PMCID: PMC9877427 DOI: 10.3389/fmed.2022.1069449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 12/23/2022] [Indexed: 01/14/2023] Open
Abstract
Disturbances of retinal perfusion are involved in the onset and maintenance of several ocular diseases, including diabetic retinopathy, glaucoma, and retinal vascular occlusion. Hence, knowledge on ocular vascular anatomy and function is highly relevant for basic research studies and for clinical judgment and treatment. The retinal vasculature is composed of the superficial, intermediate, and deep vascular layer. Detection of changes in blood flow and vascular diameter especially in smaller vessels is essential to understand and to analyze vascular diseases. Several methods to evaluate blood flow regulation in the retina have been described so far, but no gold standard has been established. For highly reliable assessment of retinal blood flow, exact determination of vessel diameter is necessary. Several measurement methods have already been reported in humans. But for further analysis of retinal vascular diseases, studies in laboratory animals, including genetically modified mice, are important. As for mice, the small vessel size is challenging requiring devices with high optic resolution. In this review, we recapitulate different methods for retinal blood flow and vessel diameter measurement. Moreover, studies in humans and in experimental animals are described.
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The Endothelial Glycocalyx and Retinal Hemodynamics. PATHOPHYSIOLOGY : THE OFFICIAL JOURNAL OF THE INTERNATIONAL SOCIETY FOR PATHOPHYSIOLOGY 2022; 29:663-677. [PMID: 36548208 PMCID: PMC9785437 DOI: 10.3390/pathophysiology29040052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 10/20/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022]
Abstract
PURPOSE Previous studies suggest that the endothelial glycocalyx adds to vascular resistance, inhibits thrombosis, and is critical for regulating homogeneous blood flow and ensuring uniform red blood cell (RBC) distribution. However, these functions and consequences of the glycocalyx have not been examined in the retina. We hypothesize that the endothelial glycocalyx is a critical regulator of retinal hemodynamics and perfusion and decreases the propensity for retinal thrombus formation. METHODS Hyaluronidase and heparinase, which are endothelial glycocalyx-degrading enzymes, were infused into mice. Fluorescein isothiocyanate-dextran (2000 kDa) was injected to measure lumen diameter, while RBC velocity and distribution were measured using fluorescently labeled RBCs. The diameters and velocities were used to calculate retinal blood flow and shear rates. Mean circulation time was calculated by measuring the difference between arteriolar and venular mean transit times. Rose Bengal dye was infused, followed by illumination with a green light to induce thrombosis. RESULTS The acute infusion of hyaluronidase and heparinase led to significant increases in both arteriolar (7%) and venular (16%) diameters in the retina, with a tendency towards increased arteriolar velocity. In addition, the degradation caused a significant decrease in the venular shear rate (14%). The enzyme infusion resulted in substantial increases in total retinal blood flow (26%) and retinal microhematocrit but no changes in the mean circulation time through the retina. We also observed an enhanced propensity for retinal thrombus formation with the removal of the glycocalyx. CONCLUSIONS Our data suggest that acute degradation of the glycocalyx can cause significant changes in retinal hemodynamics, with increases in vessel diameter, blood flow, microhematocrit, pro-thrombotic conditions, and decreases in venular shear rate.
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Kaur G, Song Y, Xia K, McCarthy K, Zhang F, Linhardt RJ, Harris NR. Effect of high glucose on glycosaminoglycans in cultured retinal endothelial cells and rat retina. Glycobiology 2022; 32:720-734. [PMID: 35552402 PMCID: PMC9280546 DOI: 10.1093/glycob/cwac029] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 04/07/2022] [Accepted: 04/29/2022] [Indexed: 02/07/2023] Open
Abstract
INTRODUCTION The endothelial glycocalyx regulates vascular permeability, inflammation, and coagulation, and acts as a mechanosensor. The loss of glycocalyx can cause endothelial injury and contribute to several microvascular complications and, therefore, may promote diabetic retinopathy. Studies have shown a partial loss of retinal glycocalyx in diabetes, but with few molecular details of the changes in glycosaminoglycan (GAG) composition. Therefore, the purpose of our study was to investigate the effect of hyperglycemia on GAGs of the retinal endothelial glycocalyx. METHODS GAGs were isolated from rat retinal microvascular endothelial cells (RRMECs), media, and retinas, followed by liquid chromatography-mass spectrometry assays. Quantitative real-time polymerase chain reaction was used to study mRNA transcripts of the enzymes involved in GAG biosynthesis. RESULTS AND CONCLUSIONS Hyperglycemia significantly increased the shedding of heparan sulfate (HS), chondroitin sulfate (CS), and hyaluronic acid (HA). There were no changes to the levels of HS in RRMEC monolayers grown in high-glucose media, but the levels of CS and HA decreased dramatically. Similarly, while HA decreased in the retinas of diabetic rats, the total GAG and CS levels increased. Hyperglycemia in RRMECs caused a significant increase in the mRNA levels of the enzymes involved in GAG biosynthesis (including EXTL-1,2,3, EXT-1,2, ChSY-1,3, and HAS-2,3), with these increases potentially being compensatory responses to overall glycocalyx loss. Both RRMECs and retinas of diabetic rats exhibited glucose-induced alterations in the disaccharide compositions and sulfation of HS and CS, with the changes in sulfation including N,6-O-sulfation on HS and 4-O-sulfation on CS.
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Affiliation(s)
- Gaganpreet Kaur
- Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center-Shreveport, Shreveport, LA 71103, USA
| | - Yuefan Song
- Department of Chemistry and Chemical Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Ke Xia
- Department of Chemistry and Chemical Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Kevin McCarthy
- Department of Cellular Biology and Anatomy, Louisiana State University Health Sciences Center-Shreveport, Shreveport, LA 71103, USA
| | - Fuming Zhang
- Department of Chemistry and Chemical Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Robert J Linhardt
- Department of Chemistry and Chemical Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Norman R Harris
- Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center-Shreveport, Shreveport, LA 71103, USA
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Kaur G, Rogers J, Rashdan NA, Cruz-Topete D, Pattillo CB, Hartson SD, Harris NR. Hyperglycemia-induced effects on glycocalyx components in the retina. Exp Eye Res 2021; 213:108846. [PMID: 34801534 PMCID: PMC8665121 DOI: 10.1016/j.exer.2021.108846] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 11/10/2021] [Accepted: 11/12/2021] [Indexed: 11/19/2022]
Abstract
PURPOSE Diabetic retinopathy is a vision-threatening complication of diabetes characterized by endothelial injury and vascular dysfunction. The loss of the endothelial glycocalyx, a dynamic layer lining all endothelial cells, contributes to several microvascular pathologies, including an increase in vascular permeability, leukocyte plugging, and capillary occlusion, and may drive the progression of retinopathy. Previously, a significant decrease in glycocalyx thickness has been observed in diabetic retinas. However, the effects of diabetes on specific components of the retinal glycocalyx have not yet been studied. Therefore, the aim of our study was to investigate changes in synthesis, expression, and shedding of retinal glycocalyx components induced by hyperglycemia, which could provide a novel therapeutic target for diabetic retinopathy. METHODS Primary rat retinal microvascular endothelial cells (RRMECs) were grown under normal glucose (5 mM) or high-glucose (25 mM) conditions for 6 days. The mRNA and protein levels of the glycocalyx components were examined using qRT-PCR and Western blot analysis, respectively. Further, mass spectrometry was used to analyze protein intensities of core proteins. In addition, the streptozotocin-induced Type 1 diabetic rat model was used to study changes in the expression of the retinal glycocalyx in vivo. The shedding of the glycocalyx was studied in both culture medium and in plasma using Western blot analysis. RESULTS A significant increase in the shedding of syndecan-1 and CD44 was observed both in vitro and in vivo under high-glucose conditions. The mRNA levels of syndecan-3 were significantly lower in the RRMECs grown under high glucose conditions, whereas those of syndecan-1, syndecan-2, syndecan-4, glypican-1, glypican-3, and CD44 were significantly higher. The protein expression of syndecan-3 and glypican-1 in RRMECs was reduced considerably following exposure to high glucose, whereas that of syndecan-1 and CD44 increased significantly. In addition, mass spectrometry data also suggests a significant increase in syndecan-4 and a significant decrease in glypican-3 protein levels with high glucose stimulation. In vivo, our data also suggest a significant decrease in the mRNA transcripts of syndecan-3 and an increase in mRNA levels of glypican-1 and CD44 in the retinas of diabetic rats. The diabetic rats exhibited a significant reduction in the retinal expression of syndecan-3 and CD44. However, the expression of syndecan-1 and glypican-1 increased significantly in the diabetic retina. CONCLUSIONS One of the main findings of our study was the considerable diversity of glucose-induced changes in expression and shedding of various components of endothelial glycocalyx, for example, increased endothelial and retinal syndecan-1, but decreased endothelial and retinal syndecan-3. This indicates that the reported decrease in the retinal glycocalyx in diabetes in not a result of a non-specific shedding mechanism. Moreover, mRNA measurements indicated a similar diversity, with increases in endothelial and/or retinal levels of syndecan-1, glypican-1, and CD44, but a decrease for syndecan-3, with these increases in mRNA potentially a compensatory reaction to the overall loss of glycocalyx.
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Affiliation(s)
- Gaganpreet Kaur
- Louisiana State University Health Science Center-Shreveport, LA, Department of Molecular and Cellular Physiology, USA
| | - Janet Rogers
- Oklahoma State University, OK, Department of Biochemistry and Molecular Biology, USA
| | - Nabil A Rashdan
- Louisiana State University Health Science Center-Shreveport, LA, Department of Molecular and Cellular Physiology, USA
| | - Diana Cruz-Topete
- Louisiana State University Health Science Center-Shreveport, LA, Department of Molecular and Cellular Physiology, USA
| | - Christopher B Pattillo
- Louisiana State University Health Science Center-Shreveport, LA, Department of Molecular and Cellular Physiology, USA
| | - Steven D Hartson
- Oklahoma State University, OK, Department of Biochemistry and Molecular Biology, USA
| | - Norman R Harris
- Louisiana State University Health Science Center-Shreveport, LA, Department of Molecular and Cellular Physiology, USA.
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Eshaq RS, Harris NR. The role of tumor necrosis factor-α and interferon-γ in the hyperglycemia-induced ubiquitination and loss of platelet endothelial cell adhesion molecule-1 in rat retinal endothelial cells. Microcirculation 2021; 28:e12717. [PMID: 34008903 PMCID: PMC10078990 DOI: 10.1111/micc.12717] [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: 10/26/2020] [Revised: 05/03/2021] [Accepted: 05/11/2021] [Indexed: 11/25/2022]
Abstract
OBJECTIVE This study aimed to investigate the role of the hyperglycemia-induced increase in tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) in the ubiquitination and degradation of platelet endothelial cell adhesion molecule-1 (PECAM-1) in the diabetic retina. METHODS Type I diabetes was induced in rats by the injection of streptozotocin, with age-matched non-diabetic rats as controls. Primary rat retinal microvascular endothelial cells were grown in normal or high glucose media for 6 days or in normal glucose media for 24 h with addition of TNF-α and/or IFN-γ. PECAM-1, TNF-α, IFN-γ, and ubiquitin levels were assessed using Western blotting, immunofluorescence, and immunoprecipitation assays. Additionally, proteasome activity was assessed both in vivo and in vitro. RESULTS Under hyperglycemic conditions, total ubiquitination levels in the retina and RRMECs, and PECAM-1 ubiquitination levels in RRMECs, were significantly increased. Additionally, TNF-α and IFN-γ levels were significantly increased under hyperglycemic conditions. PECAM-1 levels in RRMECs treated with TNF-α and/or IFN-γ were significantly decreased. Moreover, there was a significant decrease in proteasome activity in the diabetic retina, hyperglycemic RRMECs, and RRMECs treated with TNF-α or IFN-γ. CONCLUSION Tumor necrosis factor-α and IFN-γ may contribute to the hyperglycemia-induced loss of PECAM-1 in retinal endothelial cells, possibly by upregulating PECAM-1 ubiquitination.
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Affiliation(s)
- Randa S Eshaq
- Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center-Shreveport, Shreveport, LA, USA
| | - Norman R Harris
- Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center-Shreveport, Shreveport, LA, USA
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Eshaq RS, Watts MN, Carter PR, Leskova W, Aw TY, Alexander JS, Harris NR. Candesartan Normalizes Changes in Retinal Blood Flow and p22phox in the Diabetic Rat Retina. PATHOPHYSIOLOGY 2021; 28:86-97. [PMID: 35366272 PMCID: PMC8830460 DOI: 10.3390/pathophysiology28010008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 02/25/2021] [Accepted: 02/25/2021] [Indexed: 11/23/2022] Open
Abstract
Angiotensin II has been implicated in the progression of diabetic retinopathy, which is characterized by altered microvasculature, oxidative stress, and neuronal dysfunction. The signaling induced by angiotensin II can occur not only via receptor-mediated calcium release that causes vascular constriction, but also through a pathway whereby angiotensin II activates NADPH oxidase to elicit the formation of reactive oxygen species (ROS). In the current study, we administered the angiotensin II receptor antagonist candesartan (or vehicle, in untreated animals) in a rat model of type 1 diabetes in which hyperglycemia was induced by injection of streptozotocin (STZ). Eight weeks after the STZ injection, untreated diabetic rats were found to have a significant increase in tissue levels of angiotensin converting enzyme (ACE; p < 0.05) compared to non-diabetic controls, a 33% decrease in retinal blood flow rate (p < 0.001), and a dramatic increase in p22phox (a subunit of the NADPH oxidase). The decrease in retinal blood flow, and the increases in retinal ACE and p22phox in the diabetic rats, were all significantly attenuated (p < 0.05) by the administration of candesartan in drinking water within one week. Neither STZ nor candesartan induced any changes in tissue levels of superoxide dismutase (SOD-1), 4-hydroxynonenal (4-HNE), or nitrotyrosine. We conclude that one additional benefit of candesartan (and other angiotensin II antagonists) may be to normalize retinal blood flow, which may have clinical benefits in diabetic retinopathy.
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Abstract
Based on clinical findings, diabetic retinopathy (DR) has traditionally been defined as a retinal microvasculopathy. Retinal neuronal dysfunction is now recognized as an early event in the diabetic retina before development of overt DR. While detrimental effects of diabetes on the survival and function of inner retinal cells, such as retinal ganglion cells and amacrine cells, are widely recognized, evidence that photoreceptors in the outer retina undergo early alterations in diabetes has emerged more recently. We review data from preclinical and clinical studies demonstrating a conserved reduction of electrophysiological function in diabetic retinas, as well as evidence for photoreceptor loss. Complementing in vivo studies, we discuss the ex vivo electroretinography technique as a useful method to investigate photoreceptor function in isolated retinas from diabetic animal models. Finally, we consider the possibility that early photoreceptor pathology contributes to the progression of DR, and discuss possible mechanisms of photoreceptor damage in the diabetic retina, such as enhanced production of reactive oxygen species and other inflammatory factors whose detrimental effects may be augmented by phototransduction.
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Leskova W, Warar R, Harris NR. Altered Retinal Hemodynamics and Mean Circulation Time in Spontaneously Hypertensive Rats. Invest Ophthalmol Vis Sci 2020; 61:12. [PMID: 32761138 PMCID: PMC7441299 DOI: 10.1167/iovs.61.10.12] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Purpose Although it is known that the retinal arteriolar vasculature is constricted in hypertension, the details of retinal hemodynamics and perfusion of the retinal circulation have yet to be adequately characterized. Methods Male and female spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) controls were anesthetized before measurements of mean arterial blood pressure and preparation for intravital microscopy of the retinal microcirculation. Retinal vascular velocities were measured with the use of fluorescent microspheres, and diameters and mean circulation times were measured after the infusion of fluorescent dextran. Arteriolar and venular shear rates were calculated from the ratio of velocity to diameter. Results In the retinas of SHR, velocities were elevated (compared with control WKY) in arterioles, but not in venules. Both arteriolar and venular diameters were significantly smaller in SHR versus WKY, with substantial increases in shear rates. Despite a tendency toward lower retinal blood flow rates, the mean circulation time through the SHR retina was much faster than can be explained by the measured arteriolar and venular velocities. Conclusions The pattern of hypertension-induced increases in blood velocity, dissipating from the arteriolar to venular side of the retinal circulation, indicates a potential transfer of the extra kinetic energy through the vasculature. The combination of elevated velocities through narrower retinal arterioles resulted in a markedly higher level of wall shear rate that may induce changes in the vessel wall. Finally, significantly more rapid transits through the hypertensive retina could be a result of altered blood flow distribution.
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Wright WS, Eshaq RS, Lee M, Kaur G, Harris NR. Retinal Physiology and Circulation: Effect of Diabetes. Compr Physiol 2020; 10:933-974. [PMID: 32941691 PMCID: PMC10088460 DOI: 10.1002/cphy.c190021] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
In this article, we present a discussion of diabetes and its complications, including the macrovascular and microvascular effects, with the latter of consequence to the retina. We will discuss the anatomy and physiology of the retina, including aspects of metabolism and mechanisms of oxygenation, with the latter accomplished via a combination of the retinal and choroidal blood circulations. Both of these vasculatures are altered in diabetes, with the retinal circulation intimately involved in the pathology of diabetic retinopathy. The later stages of diabetic retinopathy involve poorly controlled angiogenesis that is of great concern, but in our discussion, we will focus more on several alterations in the retinal circulation occurring earlier in the progression of disease, including reductions in blood flow and a possible redistribution of perfusion that may leave some areas of the retina ischemic and hypoxic. Finally, we include in this article a more recent area of investigation regarding the diabetic retinal vasculature, that is, the alterations to the endothelial surface layer that normally plays a vital role in maintaining physiological functions. © 2020 American Physiological Society. Compr Physiol 10:933-974, 2020.
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Affiliation(s)
- William S Wright
- Department of Biomedical Sciences, University of South Carolina School of Medicine Greenville, Greenville, South Carolina, USA
| | - Randa S Eshaq
- Department of Molecular and Cellular Physiology, Louisiana State University Health Shreveport, Shreveport, Louisiana, USA
| | - Minsup Lee
- Department of Molecular and Cellular Physiology, Louisiana State University Health Shreveport, Shreveport, Louisiana, USA
| | - Gaganpreet Kaur
- Department of Molecular and Cellular Physiology, Louisiana State University Health Shreveport, Shreveport, Louisiana, USA
| | - Norman R Harris
- Department of Molecular and Cellular Physiology, Louisiana State University Health Shreveport, Shreveport, Louisiana, USA
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Harris NR, Leskova W, Kaur G, Eshaq RS, Carter PR. Blood flow distribution and the endothelial surface layer in the diabetic retina. Biorheology 2020; 56:181-189. [PMID: 30958328 PMCID: PMC10082436 DOI: 10.3233/bir-180200] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Diabetic retinopathy is known as a microvascular complication of hyperglycemia, with a breakdown of the blood-retinal barrier, loss of pericytes, formation of microhemorrhages, early decreases in perfusion and areas of ischemia, with the latter speculated to induce the eventual proliferative, angiogenic phase of the disease. Our animal models of diabetic retinopathy demonstrate similar decreases in retinal blood flow as seen in the early stages of diabetes in humans. Our studies also show an alteration in the retinal distribution of red blood cells, with the deep capillary layer receiving a reduced fraction, and with flow being diverted more towards the superficial vascular layer. Normal red blood cell distribution is dependent on the presence of the endothelial surface layer, specifically the glycocalyx, which has been reported to be partially lost in the diabetic retina of both humans and animals. This review addresses these two phenomena in diabetes: altered perfusion patterns and loss of the glycocalyx, with a possible connection between the two.
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Affiliation(s)
- Norman R Harris
- Department of Molecular & Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA, USA
| | - Wendy Leskova
- Department of Molecular & Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA, USA
| | - Gaganpreet Kaur
- Department of Molecular & Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA, USA
| | - Randa S Eshaq
- Department of Molecular & Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA, USA
| | - Patsy R Carter
- Department of Molecular & Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA, USA
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Eshaq RS, Harris NR. Loss of Platelet Endothelial Cell Adhesion Molecule-1 (PECAM-1) in the Diabetic Retina: Role of Matrix Metalloproteinases. Invest Ophthalmol Vis Sci 2019; 60:748-760. [PMID: 30793207 PMCID: PMC6385619 DOI: 10.1167/iovs.18-25068] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To test the hypothesis that high glucose and matrix metalloproteinases (MMPs) contribute to the diabetes-induced loss of platelet endothelial cell adhesion molecule-1 (PECAM-1) in the retinal microvasculature. Methods PECAM-1 and MMP protein, activity, and interactions with PECAM-1 were assessed using western blotting, zymography, immunofluorescence, or coimmunoprecipitation assays. These assays were conducted using primary rat retinal microvascular endothelial cells (RRMECs) grown either in normal glucose (5 mM) or high glucose (25 mM) conditions and using retinas collected from streptozotocin-induced diabetic or control rats. The broad-spectrum MMP inhibitor GM6001 was administered in vivo and in vitro to ascertain the role of MMPs in the hyperglycemia-induced loss of PECAM-1. Results A dramatic decrease in PECAM-1 (western blotting, immunofluorescence) was observed in both the diabetic retina and in hyperglycemic RRMECs. The decrease in PECAM-1 was accompanied by a significant increase in the presence and activity of matrix metalloproteinase-2 (MMP-2) (but not matrix metalloproteinase-9 [MMP-9]) in the diabetic plasma (P < 0.05) and in hyperglycemic RRMECs (P < 0.05). Moreover, RRMEC PECAM-1 significantly decreased when treated with plasma collected from diabetic rats. Several MMP-2 cleavage sites on PECAM-1 were identified using in silico analysis. Moreover, PECAM-1/MMP-2 interactions were confirmed using coimmunoprecipitation. PECAM-1 was significantly decreased in RRMECs treated with MMP-2 (P < 0.05), but became comparable to controls with the MMP inhibitor GM6001 in both the diabetic retina and hyperglycemic RRMECs. Conclusions These results indicate a possible role of MMP-2 in hyperglycemia-induced PECAM-1 loss in retinal endothelial cells.
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Affiliation(s)
- Randa S Eshaq
- Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States
| | - Norman R Harris
- Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States
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Clinical Outcomes and Intraocular Pressure Control After Scleral-glued Intraocular Lens Insertion in Eyes With Pseudoexfoliation. J Glaucoma 2018; 27:164-169. [DOI: 10.1097/ijg.0000000000000839] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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15
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Hui F, Nguyen CTO, He Z, Vingrys AJ, Gurrell R, Fish RL, Bui BV. Retinal and Cortical Blood Flow Dynamics Following Systemic Blood-Neural Barrier Disruption. Front Neurosci 2017; 11:568. [PMID: 29075176 PMCID: PMC5643486 DOI: 10.3389/fnins.2017.00568] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 09/28/2017] [Indexed: 12/11/2022] Open
Abstract
To consider whether imaging retinal vasculature may be used as a marker for cortical vessels, we compared fluorescein angiography flow dynamics before and after pharmacological disruption of blood-neural barriers. Sodium fluorescein (1%, 200 μl/kg) was intravenously delivered in anesthetized adult Long Evans rats (n = 44, brain = 18, retina = 26). In the brain cohort, a cranial window was created to allow direct visualization of surface cortical vessels. Video fluorescein angiography was captured using a rodent retinal camera at 30 frames/second and fluorescence intensity profiles were evaluated for the time to reach 50% brightness (half-rise), 50% decay (half-fall), and the plateau level of remnant fluorescence (offset, %). Cortical vessels fluoresced earlier (artery half-rise: 5.6 ± 0.2 s) and decayed faster (half-fall: 10.3 ± 0.2 s) compared to retinal vasculature. Cortical vessels also had a considerably higher offset, particularly in the capillaries/extravascular space (41.4 ± 2.7%) whereas pigment in the retina reduces such residual fluorescence. In a sub-cohort of animals, sodium deoxycholate (DOC, 0.06 M dissolved in sterile saline, 1 mL) was delivered intravenously to cause simultaneous disruption of the blood-brain and blood-retinal barriers. A separate group received saline as vehicle control. Fluorescein angiography was re-measured at 6 and 24 h after drug infusion and evaluated by comparing flow dynamics to the upper quartile (75%) of the control group. Retinal vasculature was more sensitive to DOC-induced disruption with a higher fluorescence offset at 6 h (47.3 ± 10.6%). A delayed effect was seen in cortical vessels with a higher offset evident only at 24 h (65.6 ± 10.1%). Here we have developed a method to quantitatively compare fluorescein angiography dynamics in the retina and superficial cortical vessels. Our results show that systemic disruption of blood-neural barriers causes vascular leakage in both tissues but earlier in the retina suggesting that pharmacological blood-neural barrier disruption may be detected earlier in the eye than in cortical vasculature.
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Affiliation(s)
- Flora Hui
- Department of Optometry and Vision Sciences, University of Melbourne, Melbourne, VIC, Australia
| | - Christine T. O. Nguyen
- Department of Optometry and Vision Sciences, University of Melbourne, Melbourne, VIC, Australia
| | - Zheng He
- Department of Optometry and Vision Sciences, University of Melbourne, Melbourne, VIC, Australia
| | - Algis J. Vingrys
- Department of Optometry and Vision Sciences, University of Melbourne, Melbourne, VIC, Australia
| | - Rachel Gurrell
- Neuroscience and Pain Research Unit, Pfizer, Cambridge, United Kingdom
| | - Rebecca L. Fish
- Neuroscience and Pain Research Unit, Pfizer, Cambridge, United Kingdom
| | - Bang V. Bui
- Department of Optometry and Vision Sciences, University of Melbourne, Melbourne, VIC, Australia
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Chung YR, Choi JA, Koh JY, Yoon YH. Ursodeoxycholic Acid Attenuates Endoplasmic Reticulum Stress-Related Retinal Pericyte Loss in Streptozotocin-Induced Diabetic Mice. J Diabetes Res 2017; 2017:1763292. [PMID: 28127564 PMCID: PMC5239976 DOI: 10.1155/2017/1763292] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 11/30/2016] [Indexed: 12/05/2022] Open
Abstract
Loss of pericytes, an early hallmark of diabetic retinopathy (DR), results in breakdown of the blood-retinal barrier. Endoplasmic reticulum (ER) stress may be involved in this process. The purpose of this study was to examine the effects of ursodeoxycholic acid (UDCA), a known ameliorator of ER stress, on pericyte loss in DR of streptozotocin- (STZ-) induced diabetic mice. To assess the extent of DR, the integrity of retinal vessels and density of retinal capillaries in STZ-induced diabetic mice were evaluated. Additionally, induction of ER stress and the unfolded protein response (UPR) were assessed in diabetic mice and human retinal pericytes exposed to advanced glycation end products (AGE) or modified low-density lipoprotein (mLDL). Fluorescein dye leakage during angiography and retinal capillary density were improved in UDCA-treated diabetic mice, compared to the nontreated diabetic group. Among the UPR markers, those involved in the protein kinase-like ER kinase (PERK) pathway were increased, while UDCA attenuated UPR in STZ-induced diabetic mice as well as AGE- or mLDL-exposed retinal pericytes in culture. Consequently, vascular integrity was improved and pericyte loss reduced in the retina of STZ-induced diabetic mice. Our findings suggest that UDCA might be effective in protecting against DR.
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Affiliation(s)
- Yoo-Ri Chung
- Department of Ophthalmology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
| | - Jeong A. Choi
- Neural Injury Research Center, Asan Institute for Life Sciences, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
| | - Jae-Young Koh
- Neural Injury Research Center, Asan Institute for Life Sciences, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
- Department of Neurology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
| | - Young Hee Yoon
- Department of Ophthalmology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
- *Young Hee Yoon:
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Choi JA, Chung YR, Byun HR, Park H, Koh JY, Yoon YH. The anti-ALS drug riluzole attenuates pericyte loss in the diabetic retinopathy of streptozotocin-treated mice. Toxicol Appl Pharmacol 2016; 315:80-89. [PMID: 27939241 DOI: 10.1016/j.taap.2016.12.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 11/24/2016] [Accepted: 12/05/2016] [Indexed: 01/16/2023]
Abstract
Loss of pericytes, considered an early hallmark of diabetic retinopathy, is thought to involve abnormal activation of protein kinase C (PKC). We previously showed that the anti-amyotrophic lateral sclerosis (ALS) drug riluzole functions as a PKC inhibitor. Here, we examined the effects of riluzole on pathological changes in diabetic retinopathy. Pathological endpoints examined in vivo included the number of pericytes and integrity of retinal vessels in streptozotocin (STZ)-induced diabetic mice. In addition, PKC activation and the induction of monocyte chemotactic protein (MCP1) were assessed in diabetic mice and in human retinal pericytes exposed to advanced glycation end product (AGE) or modified low-density lipoprotein (mLDL). The diameter of retinal vessels and the number of pericytes were severely reduced, and the levels of MCP1 and PKC were increased in STZ-induced diabetic mice. Administration of riluzole reversed all of these changes. Furthermore, the increased expression of MCP1 in AGE- or mLDL-treated cultured retinal pericytes was inhibited by treatment with riluzole or the PKC inhibitor GF109203X. In silico modeling showed that riluzole fits well within the catalytic pocket of PKC. Taken together, our results demonstrate that riluzole attenuates both MCP1 induction and pericyte loss in diabetic retinopathy, likely through its direct inhibitory effect on PKC.
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Affiliation(s)
- Jeong A Choi
- Neural Injury Research Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul, Republic of Korea
| | - Yoo-Ri Chung
- Department of Ophthalmology, University of Ulsan College of Medicine, Seoul, Republic of Korea
| | - Hyae-Ran Byun
- Neural Injury Research Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul, Republic of Korea
| | - Hwangseo Park
- Department of Bioscience and Biotechnology, Sejong University, Seoul, Republic of Korea
| | - Jae-Young Koh
- Neural Injury Research Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul, Republic of Korea; Department of Neurology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
| | - Young Hee Yoon
- Department of Ophthalmology, University of Ulsan College of Medicine, Seoul, Republic of Korea.
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Abstract
Blood flow is a useful indicator of the metabolic state of the retina. However, accurate measurement of retinal blood flow is difficult to achieve in practice. Most existing optical techniques used for measuring blood flow require complex assumptions and calculations. We describe here a simple and direct method for calculating absolute blood flow in vessels of all sizes in the rat retina. The method relies on ultrafast confocal line scans to track the passage of fluorescently labeled red blood cells (fRBCs). The accuracy of the blood flow measurements was verified by (1) comparing blood flow calculated independently using either flux or velocity combined with diameter measurements, (2) measuring total retinal blood flow in arterioles and venules, (3) measuring blood flow at vessel branch points, and (4) measuring changes in blood flow in response to hyperoxic and hypercapnic challenge. Confocal line scans oriented parallel and diagonal to vessels were used to compute fRBC velocity and to examine velocity profiles across the width of vessels. We demonstrate that these methods provide accurate measures of absolute blood flow and velocity in retinal vessels of all sizes.
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Hui F, Nguyen CTO, Bedggood PA, He Z, Fish RL, Gurrell R, Vingrys AJ, Bui BV. Quantitative spatial and temporal analysis of fluorescein angiography dynamics in the eye. PLoS One 2014; 9:e111330. [PMID: 25365578 PMCID: PMC4218721 DOI: 10.1371/journal.pone.0111330] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 09/22/2014] [Indexed: 12/25/2022] Open
Abstract
Purpose We describe a novel approach to analyze fluorescein angiography to investigate fluorescein flow dynamics in the rat posterior retina as well as identify abnormal areas following laser photocoagulation. Methods Experiments were undertaken in adult Long Evans rats. Using a rodent retinal camera, videos were acquired at 30 frames per second for 30 seconds following intravenous introduction of sodium fluorescein in a group of control animals (n = 14). Videos were image registered and analyzed using principle components analysis across all pixels in the field. This returns fluorescence intensity profiles from which, the half-rise (time to 50% brightness), half-fall (time for 50% decay) back to an offset (plateau level of fluorescence). We applied this analysis to video fluorescein angiography data collected 30 minutes following laser photocoagulation in a separate group of rats (n = 7). Results Pixel-by-pixel analysis of video angiography clearly delineates differences in the temporal profiles of arteries, veins and capillaries in the posterior retina. We find no difference in half-rise, half-fall or offset amongst the four quadrants (inferior, nasal, superior, temporal). We also found little difference with eccentricity. By expressing the parameters at each pixel as a function of the number of standard deviation from the average of the entire field, we could clearly identify the spatial extent of the laser injury. Conclusions This simple registration and analysis provides a way to monitor the size of vascular injury, to highlight areas of subtle vascular leakage and to quantify vascular dynamics not possible using current fluorescein angiography approaches. This can be applied in both laboratory and clinical settings for in vivo dynamic fluorescent imaging of vasculature.
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Affiliation(s)
- Flora Hui
- Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia
| | - Christine T. O. Nguyen
- Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia
| | - Phillip A. Bedggood
- Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia
| | - Zheng He
- Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia
| | - Rebecca L. Fish
- Neusentis, Pfizer Research and Development, Grant Park Science Park, Cambridge, United Kingdom
| | - Rachel Gurrell
- Neusentis, Pfizer Research and Development, Grant Park Science Park, Cambridge, United Kingdom
| | - Algis J. Vingrys
- Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia
| | - Bang V. Bui
- Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia
- * E-mail:
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Man REK, Sasongko MB, Xie J, Kawasaki R, Best WJ, Noonan JE, Luu CD, Wang JJ, Lamoureux EL. Associations of retinal oximetry in persons with diabetes. Clin Exp Ophthalmol 2014; 43:124-31. [PMID: 25041320 DOI: 10.1111/ceo.12387] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 06/23/2014] [Indexed: 01/25/2023]
Abstract
BACKGROUND There are limited data available on the variables that might affect retinal vessel oxygen saturation (SO₂) in diabetes. Therefore, the aim of this study is to assess factors associated with retinal oximetry values in persons with diabetes. DESIGN Clinic-based cross-sectional study. PARTICIPANTS Fifty-eight persons with diabetes aged 18+ years, recruited from the University of Melbourne, the Royal Victorian Eye and Ear Hospital, and St. Vincent's Hospital (Melbourne), Australia. METHODS Retinal oximetry was performed using the oximetry module of the Vesselmap system (Imedos UG, Jena, Germany) in 92 diabetic eyes. Generalized estimating equation models were used to estimate the associations between candidate variables (age; gender; retinal capillary flow; duration of diabetes; hypertension; smoking status; presence of diabetic retinopathy [DR]; glycated haemoglobin; triglyceride; total cholesterol; finger SO₂ and ocular perfusion pressure) with retinal oximetry measures. MAIN OUTCOME MEASURE Arteriolar SO₂, venular SO₂ and the arterio-venous (A-V) difference. RESULTS Of the candidate factors assessed, only the presence of DR was significantly associated with increased venular SO₂ and decreased A-V difference in unadjusted analyses. In models adjusting for age and gender and significant variables from unadjusted analyses, compared with no DR, the presence of DR was significantly associated with greater retinal venular SO₂ values (β = 3.65%, 95% confidence interval: 0.67-6.63%) and decreased A-V difference (β = -2.00%, 95% confidence interval: -3.46 to -0.53%). CONCLUSION In patients with diabetes, eyes with DR were associated with increased venular SO₂ and decreased A-V difference compared with eyes without DR, suggesting an altered metabolic state in DR.
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Affiliation(s)
- Ryan E K Man
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, University of Melbourne, Melbourne, Victoria
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Zhi Z, Chao JR, Wietecha T, Hudkins KL, Alpers CE, Wang RK. Noninvasive imaging of retinal morphology and microvasculature in obese mice using optical coherence tomography and optical microangiography. Invest Ophthalmol Vis Sci 2014; 55:1024-30. [PMID: 24458155 DOI: 10.1167/iovs.13-12864] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
PURPOSE To evaluate early diabetes-induced changes in retinal thickness and microvasculature in a type 2 diabetic mouse model by using optical coherence tomography (OCT)/optical microangiography (OMAG). METHODS Twenty-two-week-old obese (OB) BTBR mice (n = 10) and wild-type (WT) control mice (n = 10) were imaged. Three-dimensional (3D) data volumes were captured with spectral domain OCT using an ultrahigh-sensitive OMAG scanning protocol for 3D volumetric angiography of the retina and dense A-scan protocol for measurement of the total retinal blood flow (RBF) rate. The thicknesses of the nerve fiber layer (NFL) and that of the NFL to the inner plexiform layer (IPL) were measured and compared between OB and WT mice. The linear capillary densities within intermediate and deep capillary layers were determined by the number of capillaries crossing a 500-μm line. The RBF rate was evaluated using an en face Doppler approach. These quantitative measurements were compared between OB and WT mice. RESULTS The retinal thickness of the NFL to IPL was significantly reduced in OB mice (P < 0.01) compared to that in WT mice, whereas the NFL thickness between the two was unchanged. 3D depth-resolved OMAG angiography revealed the first in vivo 3D model of mouse retinal microcirculation. Although no obvious differences in capillary vessel densities of the intermediate and deep capillary layers were detected between normal and OB mice, the total RBF rate was significantly lower (P < 0.05) in OB mice than in WT mice. CONCLUSIONS We conclude that OB BTBR mice have significantly reduced NFL-IPL thicknesses and total RBF rates compared with those of WT mice, as imaged by OCT/OMAG. OMAG provides an unprecedented capability for high-resolution depth-resolved imaging of mouse retinal vessels and blood flow that may play a pivotal role in providing a noninvasive method for detecting early microvascular changes in patients with diabetic retinopathy.
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Affiliation(s)
- Zhongwei Zhi
- Department of Bioengineering, University of Washington, Seattle, Washington
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