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Norrie JL, Lupo M, Shirinifard A, Djekidel N, Ramirez C, Xu B, Dundee JM, Dyer MA. Latent Epigenetic Programs in Müller Glia Contribute to Stress, Injury, and Disease Response in the Retina. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.15.562396. [PMID: 37905050 PMCID: PMC10614790 DOI: 10.1101/2023.10.15.562396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Previous studies have demonstrated the dynamic changes in chromatin structure during retinal development that correlate with changes in gene expression. However, a major limitation of those prior studies was the lack of cellular resolution. Here, we integrate single-cell (sc) RNA-seq and scATAC-seq with bulk retinal data sets to identify cell type-specific changes in the chromatin structure during development. Although most genes' promoter activity is strongly correlated with chromatin accessibility, we discovered several hundred genes that were transcriptionally silent but had accessible chromatin at their promoters. Most of those silent/accessible gene promoters were in the Müller glial cells. The Müller cells are radial glia of the retina and perform a variety of essential functions to maintain retinal homeostasis and respond to stress, injury, or disease. The silent/accessible genes in Müller glia are enriched in pathways related to inflammation, angiogenesis, and other types of cell-cell signaling and were rapidly activated when we tested 15 different physiologically relevant conditions to mimic retinal stress, injury, or disease in human and murine retinae. We refer to these as "pliancy genes" because they allow the Müller glia to rapidly change their gene expression and cellular state in response to different types of retinal insults. The Müller glial cell pliancy program is established during development, and we demonstrate that pliancy genes are necessary and sufficient for regulating inflammation in the murine retina in vivo. In zebrafish, Müller glia can de-differentiate and form retinal progenitor cells that replace lost neurons. The pro-inflammatory pliancy gene cascade is not activated in zebrafish Müller glia following injury, and we propose a model in which species-specific pliancy programs underly the differential response to retinal damage in species that can regenerate retinal neurons (zebrafish) versus those that cannot (humans and mice).
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2
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Wong NK, Yip SP, Huang CL. Establishing Functional Retina in a Dish: Progress and Promises of Induced Pluripotent Stem Cell-Based Retinal Neuron Differentiation. Int J Mol Sci 2023; 24:13652. [PMID: 37686457 PMCID: PMC10487913 DOI: 10.3390/ijms241713652] [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: 08/03/2023] [Revised: 08/28/2023] [Accepted: 08/30/2023] [Indexed: 09/10/2023] Open
Abstract
The human eye plays a critical role in vision perception, but various retinal degenerative diseases such as retinitis pigmentosa (RP), glaucoma, and age-related macular degeneration (AMD) can lead to vision loss or blindness. Although progress has been made in understanding retinal development and in clinical research, current treatments remain inadequate for curing or reversing these degenerative conditions. Animal models have limited relevance to humans, and obtaining human eye tissue samples is challenging due to ethical and legal considerations. Consequently, researchers have turned to stem cell-based approaches, specifically induced pluripotent stem cells (iPSCs), to generate distinct retinal cell populations and develop cell replacement therapies. iPSCs offer a novel platform for studying the key stages of human retinogenesis and disease-specific mechanisms. Stem cell technology has facilitated the production of diverse retinal cell types, including retinal ganglion cells (RGCs) and photoreceptors, and the development of retinal organoids has emerged as a valuable in vitro tool for investigating retinal neuron differentiation and modeling retinal diseases. This review focuses on the protocols, culture conditions, and techniques employed in differentiating retinal neurons from iPSCs. Furthermore, it emphasizes the significance of molecular and functional validation of the differentiated cells.
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Affiliation(s)
- Nonthaphat Kent Wong
- Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong, China;
- Centre for Eye and Vision Research (CEVR), Hong Kong Science Park, Hong Kong, China
| | - Shea Ping Yip
- Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong, China;
- Centre for Eye and Vision Research (CEVR), Hong Kong Science Park, Hong Kong, China
| | - Chien-Ling Huang
- Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong, China;
- Centre for Eye and Vision Research (CEVR), Hong Kong Science Park, Hong Kong, China
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3
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Gongal D, Thakur S, Panse A, Shankarrao P, Stark JA, Hetling JR, Ozgen B, Foster CD. Thermal finite element analysis of localized hypothermia treatment of the human eye. Med Eng Phys 2023; 111:103928. [PMID: 36792243 DOI: 10.1016/j.medengphy.2022.103928] [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: 02/08/2022] [Revised: 11/11/2022] [Accepted: 11/20/2022] [Indexed: 11/26/2022]
Abstract
Localized hypothermia treatment can reduce the risk of vision loss due to ocular trauma. Hypothermia reduces inflammation and metabolic rate, and improves blood flow to prevent nerve and tissue damage. This paper presents a finite element thermal analysis to determine the efficacy of local hypothermia treatment administered using a scleral eye contact ring that acts as a heat sink. A realistic model of the human eye orbit, including fat and muscle, is created using MRI scans. A simplified CAD-based model is also created based on the first model. A transient analysis is performed by lowering the contact surface between the device and the eye to 4∘C. The study shows that the device lowers the temperature of the optic nerve head to a therapeutic range of 32-34∘C in less than 10 min of treatment, hence supporting the efficacy of such a device.
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Affiliation(s)
- D Gongal
- Department of Civil and Materials Engineering, University of Illinois at Chicago, Chicago, IL, USA
| | - S Thakur
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL, USA
| | - A Panse
- Department of Civil and Materials Engineering, University of Illinois at Chicago, Chicago, IL, USA
| | - P Shankarrao
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL, USA
| | - J A Stark
- Department of Civil and Materials Engineering, University of Illinois at Chicago, Chicago, IL, USA
| | - J R Hetling
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA; Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - B Ozgen
- Department of Radiology, Division of Neuroradiology, University of Illinois at Chicago, Chicago, IL, USA
| | - C D Foster
- Department of Civil and Materials Engineering, University of Illinois at Chicago, Chicago, IL, USA.
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Schnichels S, Schultheiss M, Klemm P, Blak M, Herrmann T, Melchinger M, Bartz-Schmidt KU, Löscher M, Zeck G, Spitzer MS, Hurst J. Cyclosporine A Protects Retinal Explants against Hypoxia. Int J Mol Sci 2021; 22:ijms221910196. [PMID: 34638537 PMCID: PMC8508578 DOI: 10.3390/ijms221910196] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 09/14/2021] [Accepted: 09/15/2021] [Indexed: 11/16/2022] Open
Abstract
The retina is a complex neurological tissue and is extremely sensitive to an insufficient supply of oxygen. Hypoxia plays a major role in several retinal diseases, and often results in the loss of cells that are essential for vision. Cyclosporine A (CsA) is a widely used immunosuppressive drug. Furthermore, treatment with CsA has neuroprotective effects in several neurologic disorders. No data are currently available on the tolerated concentration of CsA when applied to the retina. To reveal the most effective dose, retinal explants from rat eyes were exposed to different CsA concentrations (1-9 µg/mL). Immunohistochemistry with brain-specific homeobox/POU domain protein 3a (Brn3a) and TUNEL staining was performed to determine the percentage of total and apoptotic retinal ganglion cells (RGCs), as well as the responses of micro- and macroglial cells. Furthermore, optical coherence tomography (OCT) scans were performed to measure the changes in retinal thickness, and recordings with multielectrode array (MEA) were performed to evaluate spontaneous RGC spiking. To examine the neuroprotective effects, retinas were subjected to a hypoxic insult by placing them in a nitrogen-streamed hypoxic chamber prior to CsA treatment. In the biocompatibility tests, the different CsA concentrations had no negative effect on RGCs and microglia. Neuroprotective effects after a hypoxic insult on RGCs was demonstrated at a concentration of 9 µg/mL CsA. CsA counteracted the hypoxia-induced loss of RGCs, reduced the percentage of TUNEL+ RGCs, and prevented a decrease in retinal thickness. Taken together, the results of this study suggest that CsA can effectively protect RGCs from hypoxia, and the administered concentrations were well tolerated. Further in vivo studies are needed to determine whether local CsA treatment may be a suitable option for hypoxic retinal diseases.
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Affiliation(s)
- Sven Schnichels
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, 72076 Tübingen, Germany; (S.S.); (P.K.); (M.B.); (M.M.); (K.-U.B.-S.); (M.L.); (M.S.S.)
| | - Maximilian Schultheiss
- Clinic for Ophthalmology, University Medical Center Hamburg-Eppendorf (UKE), 20246 Hamburg, Germany;
| | - Patricia Klemm
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, 72076 Tübingen, Germany; (S.S.); (P.K.); (M.B.); (M.M.); (K.-U.B.-S.); (M.L.); (M.S.S.)
| | - Matthias Blak
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, 72076 Tübingen, Germany; (S.S.); (P.K.); (M.B.); (M.M.); (K.-U.B.-S.); (M.L.); (M.S.S.)
- Department of Ophthalmology, Klinikum Stuttgart, 70174 Stuttgart, Germany
| | - Thoralf Herrmann
- NMI Natural and Medical Sciences Institute, University of Tübingen, 72770 Reutlingen, Germany;
| | - Marion Melchinger
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, 72076 Tübingen, Germany; (S.S.); (P.K.); (M.B.); (M.M.); (K.-U.B.-S.); (M.L.); (M.S.S.)
| | - Karl-Ulrich Bartz-Schmidt
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, 72076 Tübingen, Germany; (S.S.); (P.K.); (M.B.); (M.M.); (K.-U.B.-S.); (M.L.); (M.S.S.)
| | - Marina Löscher
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, 72076 Tübingen, Germany; (S.S.); (P.K.); (M.B.); (M.M.); (K.-U.B.-S.); (M.L.); (M.S.S.)
| | - Günther Zeck
- Institute of Electrodynamics, Microwave and Circuit Engineering, TU Wien, 1040 Vienna, Austria;
| | - Martin Stehphan Spitzer
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, 72076 Tübingen, Germany; (S.S.); (P.K.); (M.B.); (M.M.); (K.-U.B.-S.); (M.L.); (M.S.S.)
- Clinic for Ophthalmology, University Medical Center Hamburg-Eppendorf (UKE), 20246 Hamburg, Germany;
| | - José Hurst
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, 72076 Tübingen, Germany; (S.S.); (P.K.); (M.B.); (M.M.); (K.-U.B.-S.); (M.L.); (M.S.S.)
- Correspondence: ; Tel.: +49-7071/29-87-883
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Svare F, Åkerström B, Ghosh F. It's About Time: Time-Dependent Tissue Damage in the Adult Porcine Retina After Enucleation. Cells Tissues Organs 2021; 210:58-65. [PMID: 34038912 DOI: 10.1159/000514795] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 01/22/2021] [Indexed: 11/19/2022] Open
Abstract
The ex vivo large animal retina is extensively used in research ranging from discovery of disease mechanisms to future treatment paradigms. Due to limited standardization when harvesting the tissue, the time after enucleation is often extended for several hours, a factor that so far has not yet been fully characterized. The purpose of this study was to investigate the relationship between time after enucleation and retinal tissue damage. Adult, porcine retinal explants were dissected and fixed 90 or 240 min after enucleation. In a separate experiment, explants were cultured for 48 h, following dissection either 90 or 240 min after enucleation. Retinas were analyzed morphologically using hematoxylin and eosin for overall tissue damage, TUNEL staining for detection of apoptosis, and RBPMS immunohistochemistry for evaluation of ganglion cell survival. In addition, medium from the cultured explants was sampled after 2, 24, and 48 h of culture and assessed for the cell damage marker lactate dehydrogenase (LDH). Retinas examined 240 min after enucleation displayed a significant increase in overall tissue damage, increased apoptosis, and decreased ganglion cell survival compared with 90-min counterparts. In the culture experiment, no significant difference in overall tissue damage was found between the 2 groups, however, apoptosis was significantly increased, and ganglion cell survival decreased in the cultured 240-min group. In addition, a significantly increased LDH medium activity was found in the 240-min group compared with the 90-min counterpart at all time points. The adult porcine retina is relatively resistant to tissue damage 90 min after enucleation but displays distinct signs of injury after 240 min. The importance of these time points is further highlighted when retinal explants are cultured. Our results strongly suggest that time after enucleation is a crucial factor that should be considered in experiments involving the ex vivo adult porcine retina.
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Affiliation(s)
- Frida Svare
- Department of Ophthalmology, Lund University, Lund, Sweden
| | - Bo Åkerström
- Section for Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden
| | - Fredrik Ghosh
- Department of Ophthalmology, Lund University, Lund, Sweden
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Hurst J, Fietz A, Tsai T, Joachim SC, Schnichels S. Organ Cultures for Retinal Diseases. Front Neurosci 2020; 14:583392. [PMID: 33324149 PMCID: PMC7724035 DOI: 10.3389/fnins.2020.583392] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 10/13/2020] [Indexed: 12/18/2022] Open
Abstract
The successful development of novel therapies is closely linked with understanding the underlying pathomechanisms of a disease. To do so, model systems that reflect human diseases and allow for the evaluation of new therapeutic approaches are needed. Yet, preclinical animal studies often have limited success in predicting human physiology, pathology, and therapeutic responses. Moreover, animal testing is facing increasing ethical and bureaucratic hurdles, while human cell cultures are limited in their ability to represent in vivo situations due to the lack of the tissue microenvironment, which may alter cellular responses. To overcome these struggles, organ cultures, especially those of complex organs such as the retina, can be used to study physiological reactions to substances or stressors. Human and animal organ cultures are now well established and recognized. This mini-review discusses how retinal organ cultures can be used to preserve tissue architecture more realistically and therefore better represent disease-related changes. It also shows how molecular biological, biochemical, and histological techniques can be combined to investigate how anatomical localization may alter cellular responses. Examples for the use of retinal organ cultures, including models to study age-related macular degeneration (AMD), retinitis pigmentosa (RP), central artery occlusion (CRAO), and glaucoma are presented, and their advantages and disadvantages are discussed. We conclude that organ cultures significantly improve our understanding of complex retinal diseases and may advance treatment testing without the need for animal testing.
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Affiliation(s)
- José Hurst
- Center for Ophthalmology, University Eye Hospital, University of Tübingen, Tübingen, Germany
| | - Agnes Fietz
- Center for Ophthalmology, University Eye Hospital, University of Tübingen, Tübingen, Germany
| | - Teresa Tsai
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Stephanie C Joachim
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Sven Schnichels
- Center for Ophthalmology, University Eye Hospital, University of Tübingen, Tübingen, Germany
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7
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Schnichels S, Paquet-Durand F, Löscher M, Tsai T, Hurst J, Joachim SC, Klettner A. Retina in a dish: Cell cultures, retinal explants and animal models for common diseases of the retina. Prog Retin Eye Res 2020; 81:100880. [PMID: 32721458 DOI: 10.1016/j.preteyeres.2020.100880] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Revised: 06/23/2020] [Accepted: 06/26/2020] [Indexed: 12/11/2022]
Abstract
For many retinal diseases, including age-related macular degeneration (AMD), glaucoma, and diabetic retinopathy (DR), the exact pathogenesis is still unclear. Moreover, the currently available therapeutic options are often unsatisfactory. Research designed to remedy this situation heavily relies on experimental animals. However, animal models often do not faithfully reproduce human disease and, currently, there is strong pressure from society to reduce animal research. Overall, this creates a need for improved disease models to understand pathologies and develop treatment options that, at the same time, require fewer or no experimental animals. Here, we review recent advances in the field of in vitro and ex vivo models for AMD, glaucoma, and DR. We highlight the difficulties associated with studies on complex diseases, in which both the initial trigger and the ensuing pathomechanisms are unclear, and then delineate which model systems are optimal for disease modelling. To this end, we present a variety of model systems, ranging from primary cell cultures, over organotypic cultures and whole eye cultures, to animal models. Specific advantages and disadvantages of such models are discussed, with a special focus on their relevance to putative in vivo disease mechanisms. In many cases, a replacement of in vivo research will mean that several different in vitro models are used in conjunction, for instance to analyze and validate causative molecular pathways. Finally, we argue that the analytical decomposition into appropriate cell and tissue model systems will allow making significant progress in our understanding of complex retinal diseases and may furthermore advance the treatment testing.
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Affiliation(s)
- Sven Schnichels
- University Eye Hospital, Centre for Ophthalmology, University of Tübingen, Germany.
| | - François Paquet-Durand
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Germany
| | - Marina Löscher
- University Eye Hospital, Centre for Ophthalmology, University of Tübingen, Germany
| | - Teresa Tsai
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Germany
| | - José Hurst
- University Eye Hospital, Centre for Ophthalmology, University of Tübingen, Germany
| | - Stephanie C Joachim
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Germany
| | - Alexa Klettner
- Department of Ophthalmology, University Medical Center, University of Kiel, Kiel, Germany
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Rouzbahani A, Khodadadi E, Fooladi M. Impact of Mild Hypothermia on Final Outcome of Patients with Acute Stroke: A Randomized Clinical Trial. INDIAN JOURNAL OF NEUROTRAUMA 2020. [DOI: 10.1055/s-0040-1713462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Abstract
Background and Aim Stroke is a sudden neurological disorder caused by disturbances in the brain blood flow and loss of normal brain function. Stroke is also the second leading cause of death worldwide. In the last two decades, among the various treatment options for stroke, hypothermia has shown the promise of improving the final outcome. This study aimed to investigate the effect of noninvasive hypothermia on the final outcome of patients with an acute stroke in Iran.
Methods In a randomized clinical trial, 60 Iranian patients diagnosed with acute stroke were enrolled in 2018. Patients were selected by convenience sampling method and then randomized in two groups as experimental (n = 30) and control (n = 30). Mild hypothermia was applied using a cooling device for 72 hours on the patients’ heads and intervention results were compared with the control group. Data were collected by using Acute Physiology and Chronic Health Evaluation III (APACHE III), Full Outline of Un-Responsiveness (FOUR), and National Institutes of Health Stroke Scale (NIHSS), and later analyzed by Statistical Package for the Social Sciences (SPSS) software version 22.
Results No significant difference was found in the mean scores of all three scales before and after the intervention in control group (p > 0.05) but statistically significant difference was found in the mean scores of all three scales for the intervention group (p < 0.05). The intervention group had an increased mean score in FOUR, while APACHE and NIHSS values dropped. Researchers found statistically significant difference between the mean scores after the intervention in the experimental group compared with the control group in all three scales (p < 0.05).
Conclusion The findings of this study indicate that hypothermia has a significant statistical and clinical effect on the acute stroke outcome and it can be argued that hypothermia therapy can increase the level of consciousness and reduce the risk of death in stroke patients.
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Affiliation(s)
- Abbas Rouzbahani
- Nursing and Midwifery School, Islamic Azad University, Urmia, Iran
| | | | - Marjaneh Fooladi
- World Wide Nursing Service Network, PLLC, El Paso, Texas, United States
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9
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Mueller-Buehl AM, Doepper H, Grauthoff S, Kiebler T, Peters L, Hurst J, Kuehn S, Bartz-Schmidt KU, Dick HB, Joachim SC, Schnichels S. Oxidative stress-induced retinal damage is prevented by mild hypothermia in an ex vivo model of cultivated porcine retinas. Clin Exp Ophthalmol 2020; 48:666-681. [PMID: 32077190 DOI: 10.1111/ceo.13731] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 01/15/2020] [Accepted: 02/17/2020] [Indexed: 12/25/2022]
Abstract
BACKGROUND Hydrogen peroxide (H2 O2 ) can be used in vitro to simulate oxidative stress. In retinal organ cultures, H2 O2 induces strong neurodegeneration of the retina. It is known that oxidative stress plays a role in the development of several retinal diseases including glaucoma and ischemia. Thus, we investigated whether processes underlying oxidative stress can be prevented by hypothermia using an ex vivo organ culture model of porcine retinas. METHODS Porcine retinal explants were cultivated for 5 and 8 days. Oxidative stress was induced via 300 μM H2 O2 on day 1 for 3 hours. Hypothermia treatment at 30°C was applied simultaneously with H2 O2 , for 3 hours. Retinal ganglion cells (RGCs), apoptosis, bipolar and cholinergic amacrine cells, microglia and macroglia were evaluated immunohistologically. Apoptosis rate was additionally analysed via western blot. RESULTS Reduced apoptosis rates through hypothermia led to a preservation of RGCs (P < .001). Amacrine cells were rescued after hypothermia treatment (P = .17), whereas bipolar cells were only protected partly. Additionally, at 8 days, microglial response due to oxidative stress was completely counteracted via hypothermia (P < .001). CONCLUSIONS H2 O2 induced strong degenerative processes in porcine retinas. The role of oxidative stress in the progression of retinal diseases makes this ex vivo organ culture model suitable to investigate new therapeutic approaches. In the present study, the damaging effect of H2 O2 to several retinal cell types was counteracted or strongly alleviated through hypothermia treatment. Especially RGCs, which are affected in glaucoma disease, were protected due to a reduced apoptosis rate through hypothermia.
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Affiliation(s)
- Ana M Mueller-Buehl
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Hannah Doepper
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Sven Grauthoff
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Tobias Kiebler
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, Tübingen, Germany
| | - Laura Peters
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - José Hurst
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, Tübingen, Germany
| | - Sandra Kuehn
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Karl U Bartz-Schmidt
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, Tübingen, Germany
| | - H Burkard Dick
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Stephanie C Joachim
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Sven Schnichels
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, Tübingen, Germany
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Species Differences in the Nutrition of Retinal Ganglion Cells among Mammals Frequently Used as Animal Models. Cells 2019; 8:cells8101254. [PMID: 31615137 PMCID: PMC6829614 DOI: 10.3390/cells8101254] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 09/26/2019] [Accepted: 10/13/2019] [Indexed: 12/23/2022] Open
Abstract
The diffusion rate for proper nutrition of the inner retina depends mainly on four factors which are discussed in this review: 1. The diffusion distance between blood and retinal ganglion cells shows morphological variants in different mammalian species, namely a choroidal nutrition type, a retinal nutrition type, and a mixture of both types. 2. Low oxygen concentration levels in the inner retina force the diffusion of oxygen especially in the choroidal nutrition type. Other nutrients might be supplied by surrounding cells, mainly Müller cells. 3. Diffusion in the eye is influenced by the intraocular pressure, which is vital for the retinal ganglion cells but might also influence their proper function. Again, the nutrition types established might explain the differences in normal intraocular pressure levels among different species. 4. Temperature is a critical feature in the eye which has to be buffered to avoid neuronal damage. The most effective buffer system is the increased blood turnover in the choroid which has to be established in all species.
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11
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Januschowski K, Szurman P, Willekens K, Bojdys MJ, Boden K. [Toxicity of heavy liquids]. Ophthalmologe 2019; 116:925-929. [PMID: 31535190 DOI: 10.1007/s00347-019-00962-0] [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: 11/30/2022]
Abstract
BACKGROUND Acute toxicity of perfluorocarbon liquids (PFCL) is a relevant problem in retinal surgery due to impurities in the medicinal product. OBJECTIVE This article gives an overview of the current problems, possible explanations, interactions with other medicinal products and approaches to improved patient safety. RESULTS Toxicity is caused by impurities in the raw material but can also be caused by interactions with other medicinal products or drugs. The current test procedures do not ideally represent the ophthalmological application but there are promising activities to set the course for the future. CONCLUSION The use of PFCL in retinal surgery is generally considered safe. Users should pay attention to the quality of medicinal products.
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Affiliation(s)
- Kai Januschowski
- Augenklinik Sulzbach, Knappschaftsklinikum Saar GmbH, An der Klinik 10, 66280, Sulzbach/Saar, Deutschland. .,Department für Augenheilkunde, Universitätsaugenklinik Tübingen, Schleichstr. 12, 72076, Tübingen, Deutschland. .,Klaus Heimann Eye Research Institute, An der Klinik 10, 66280, Sulzbach/Saar, Deutschland.
| | - Peter Szurman
- Augenklinik Sulzbach, Knappschaftsklinikum Saar GmbH, An der Klinik 10, 66280, Sulzbach/Saar, Deutschland.,Klaus Heimann Eye Research Institute, An der Klinik 10, 66280, Sulzbach/Saar, Deutschland
| | - Koen Willekens
- Department für Augenheilkunde, Universitätsaugenklinikum Löwen, Herestraat 49, 3000, Löwen, Belgien
| | - Michael J Bojdys
- Department für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489, Berlin, Deutschland
| | - Karl Boden
- Augenklinik Sulzbach, Knappschaftsklinikum Saar GmbH, An der Klinik 10, 66280, Sulzbach/Saar, Deutschland
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12
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Klemm P, Hurst J, Dias Blak M, Herrmann T, Melchinger M, Bartz-Schmidt KU, Zeck G, Schultheiss M, Spitzer MS, Schnichels S. Hypothermia protects retinal ganglion cells against hypoxia-induced cell death in a retina organ culture model. Clin Exp Ophthalmol 2019; 47:1043-1054. [PMID: 31152487 DOI: 10.1111/ceo.13565] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 05/23/2019] [Accepted: 05/28/2019] [Indexed: 12/01/2022]
Abstract
BACKGROUND Hypoxia contributes to retinal damage in several retinal diseases, including central retinal artery occlusion, with detrimental consequences like painless, monocular loss of vision. Currently, the treatment options are severely limited due to the short therapy window, as the neuronal cells, especially the retinal ganglion cells (RGCs), are irreversibly damaged within the first few hours. Hypothermia might be a possible treatment option or at least might increase the therapy window. METHODS To investigate the neuroprotective effect of hypothermia after retinal hypoxia, an easy-to-use ex vivo retinal hypoxia organ culture model developed in our laboratory was used that reliably induced retinal damage on a structural, molecular and functional level. The neuroprotective effect of hypothermia after retinal hypoxia was analysed using optical coherence tomography scans, histological stainings, quantitative real-time polymerase chain reaction, western blotting and microelectrode array recordings. RESULTS Two different hypothermic temperatures (30°C and 20°C) were evaluated, both exhibited strong neuroprotective effects. Most importantly, hypothermia increased RGC survival after retinal hypoxia. Furthermore, hypothermia counteracted the hypoxia-induced RGC death, reduced macroglia activation, attenuated retinal thinning and protected from loss of spontaneous RGC activity. CONCLUSIONS These results indicate that already a mild reduction in temperature protects the RGCs against damage and could function as a promising therapeutic option for hypoxic diseases.
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Affiliation(s)
- Patricia Klemm
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, Tübingen, Germany
| | - José Hurst
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, Tübingen, Germany
| | - Matthias Dias Blak
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, Tübingen, Germany.,Department of Ophthalmology, Klinikum Stuttgart, Stuttgart, Germany
| | - Thoralf Herrmann
- Department of Neurophysics, NMI Natural and Medical Sciences Institute, University of Tübingen, Reutlingen, Germany
| | - Marion Melchinger
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, Tübingen, Germany
| | - Karl U Bartz-Schmidt
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, Tübingen, Germany
| | - Günther Zeck
- Department of Neurophysics, NMI Natural and Medical Sciences Institute, University of Tübingen, Reutlingen, Germany
| | - Maximilian Schultheiss
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, Tübingen, Germany.,Clinic for Ophthalmology, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany
| | - Martin S Spitzer
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, Tübingen, Germany.,Clinic for Ophthalmology, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany
| | - Sven Schnichels
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, Tübingen, Germany
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13
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Maliha AM, Kuehn S, Hurst J, Herms F, Fehr M, Bartz-Schmidt KU, Dick HB, Joachim SC, Schnichels S. Diminished apoptosis in hypoxic porcine retina explant cultures through hypothermia. Sci Rep 2019; 9:4898. [PMID: 30894574 PMCID: PMC6427006 DOI: 10.1038/s41598-019-41113-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 02/13/2019] [Indexed: 12/22/2022] Open
Abstract
Simulation of hypoxic processes in vitro can be achieved through cobalt chloride (CoCl2), which induces strong neurodegeneration. Hypoxia plays an important role in the progression of several retinal diseases. Thus, we investigated whether hypoxia can be reduced by hypothermia. Porcine retinal explants were cultivated for four and eight days and hypoxia was mimicked by adding 300 µM CoCl2 from day one to day three. Hypothermia treatment (30 °C) was applied simultaneously. Retinal ganglion, bipolar and amacrine cells, as well as microglia were evaluated via immunohistological and western blot analysis. Furthermore, quantitative real-time PCR was performed to analyze cellular stress and apoptosis. In addition, the expression of specific marker for the previously described cell types were investigated. A reduction of ROS and stress markers HSP70, iNOS, HIF-1α was achieved via hypothermia. In accordance, an inhibition of apoptotic proteins (caspase 3, caspase 8) and the cell cycle arrest gene p21 was found in hypothermia treated retinae. Furthermore, neurons of the inner retina were protected by hypothermia. In this study, we demonstrate that hypothermia lowers hypoxic processes and cellular stress. Additionally, hypothermia inhibits apoptosis and protects neurons. Hence, this seems to be a promising treatment for retinal neurodegeneration.
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Affiliation(s)
- Ana M Maliha
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Sandra Kuehn
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - José Hurst
- University Eye Hospital Tübingen, Centre for Ophthalmology Tübingen, Tübingen, Germany
| | - Fenja Herms
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
- Clinic for Small Animals, University of Veterinary Medicine, Hannover, Germany
| | - Michael Fehr
- Clinic for Small Animals, University of Veterinary Medicine, Hannover, Germany
| | - Karl U Bartz-Schmidt
- University Eye Hospital Tübingen, Centre for Ophthalmology Tübingen, Tübingen, Germany
| | - H Burkhard Dick
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Stephanie C Joachim
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany.
| | - Sven Schnichels
- University Eye Hospital Tübingen, Centre for Ophthalmology Tübingen, Tübingen, Germany.
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14
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Ou J, Ball JM, Luan Y, Zhao T, Miyagishima KJ, Xu Y, Zhou H, Chen J, Merriman DK, Xie Z, Mallon BS, Li W. iPSCs from a Hibernator Provide a Platform for Studying Cold Adaptation and Its Potential Medical Applications. Cell 2018; 173:851-863.e16. [PMID: 29576452 DOI: 10.1016/j.cell.2018.03.010] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 12/12/2017] [Accepted: 03/02/2018] [Indexed: 12/22/2022]
Abstract
Hibernating mammals survive hypothermia (<10°C) without injury, a remarkable feat of cellular preservation that bears significance for potential medical applications. However, mechanisms imparting cold resistance, such as cytoskeleton stability, remain elusive. Using the first iPSC line from a hibernating mammal (13-lined ground squirrel), we uncovered cellular pathways critical for cold tolerance. Comparison between human and ground squirrel iPSC-derived neurons revealed differential mitochondrial and protein quality control responses to cold. In human iPSC-neurons, cold triggered mitochondrial stress, resulting in reactive oxygen species overproduction and lysosomal membrane permeabilization, contributing to microtubule destruction. Manipulations of these pathways endowed microtubule cold stability upon human iPSC-neurons and rat (a non-hibernator) retina, preserving its light responsiveness after prolonged cold exposure. Furthermore, these treatments significantly improved microtubule integrity in cold-stored kidneys, demonstrating the potential for prolonging shelf-life of organ transplants. Thus, ground squirrel iPSCs offer a unique platform for bringing cold-adaptive strategies from hibernators to humans in clinical applications. VIDEO ABSTRACT.
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Affiliation(s)
- Jingxing Ou
- Retinal Neurophysiology Section, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - John M Ball
- Retinal Neurophysiology Section, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Yizhao Luan
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Lab of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou 510060, China; School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China
| | - Tantai Zhao
- Retinal Neurophysiology Section, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA; Department of Ophthalmology, The Second Xiang-Ya Hospital, Central South University, Changsha 410011, China
| | - Kiyoharu J Miyagishima
- Retinal Neurophysiology Section, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Yufeng Xu
- Retinal Neurophysiology Section, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA; Department of Ophthalmology, The Second Affiliated Hospital of Zhejiang University, College of Medicine, Hangzhou 310009, China
| | - Huizhi Zhou
- Trans-NIH Center for Human Immunology, Autoimmunity, and Inflammation, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jinguo Chen
- Trans-NIH Center for Human Immunology, Autoimmunity, and Inflammation, National Institutes of Health, Bethesda, MD 20892, USA
| | - Dana K Merriman
- Department of Biology, University of Wisconsin, Oshkosh, WI 54901, USA
| | - Zhi Xie
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Lab of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou 510060, China
| | - Barbara S Mallon
- NIH Stem Cell Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Wei Li
- Retinal Neurophysiology Section, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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15
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Retinal cell death dependent reactive proliferative gliosis in the mouse retina. Sci Rep 2017; 7:9517. [PMID: 28842607 PMCID: PMC5572737 DOI: 10.1038/s41598-017-09743-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 07/31/2017] [Indexed: 12/14/2022] Open
Abstract
Neurodegeneration is a common starting point of reactive gliosis, which may have beneficial and detrimental consequences. It remains incompletely understood how distinctive pathologies and cell death processes differentially regulate glial responses. Müller glia (MG) in the retina are a prime model: Neurons are regenerated in some species, but in mammals there may be proliferative disorders and scarring. Here, we investigated the relationship between retinal damage and MG proliferation, which are both induced in a reproducible and temporal order in organotypic culture of EGF-treated mouse retina: Hypothermia pretreatment during eye dissection reduced neuronal cell death and MG proliferation; stab wounds increased both. Combined (but not separate) application of defined cell death signaling pathway inhibitors diminished neuronal cell death and maintained MG mitotically quiescent. The level of neuronal cell death determined MG activity, indicated by extracellular signal-regulated kinase (ERK) phosphorylation, and proliferation, both of which were abolished by EGFR inhibition. Our data suggest that retinal cell death, possibly either by programmed apoptosis or necrosis, primes MG to be able to transduce the EGFR–ERK activity required for cell proliferation. These results imply that cell death signaling pathways are potential targets for future therapies to prevent the proliferative gliosis frequently associated with certain neurodegenerative conditions.
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16
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Schnichels S, Blak M, Hurst J, Dorfi T, Bartz-Schmidt KU, Ziemssen F, Spitzer MS, Schultheiss M. Establishment of a retinal hypoxia organ culture model. Biol Open 2017; 6:1056-1064. [PMID: 28711869 PMCID: PMC5550914 DOI: 10.1242/bio.025429] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Hypoxia plays an important role in several retinal diseases, especially in central retinal artery occlusion (CRAO). Although CRAO has been known for over a hundred years, no cure or sufficient treatment is available. Potential therapies are being evaluated in several in vivo models or primary cultures. However, in vivo models or primary cultures are very time-consuming, expensive, and furthermore several therapies or agents cannot be tested. Therefore, we aimed to develop a standardized organotypic ex vivo retinal hypoxia model. A chamber was developed in which rat retinal explants were incubated for different hypoxia durations. Afterwards, the retinas were adjusted to normal air and incubated for 24, 48 or 72 h under standard conditions. To analyze the retinal explants, and in particular the retinal ganglion cells (RGC) immunohistology, western blot and optical coherence tomography (OCT) measurements were performed. To compare our model to a standardized degeneration model, additional retinal explants were treated with 0.5 and 1 mM glutamate. Depending on hypoxia duration and incubation time, the amount of RGCs decreased and accordingly, the amount of TUNEL-positive RGCs increased. Furthermore, β-III-tubulin expression and retinal thickness significantly decreased with longer-lasting hypoxia. The reduction of RGCs induced by 75 min of hypoxia was comparable to the one of 1 mM glutamate treatment after 24 h (20.27% versus 19.69%) and 48 h (13.41% versus 14.41%) of incubation. We successfully established a cheap, standardized, easy-to-use organotypic culture model for retinal hypoxia. We selected 75 min of hypoxia for further studies, as approximately 50% of the RGC died compared to the control group after 48 h. Summary: An easy-to-use ex vivo retinal hypoxia model is introduced that reliably induced retinal damage on a morphological (retinal thickness), and molecular (protein expression and apoptotic markers) level.
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Affiliation(s)
- S Schnichels
- Centre of Ophthalmology, University Eye Hospital Tübingen, Elfriede-Aulhorn-Str. 7, D-72076 Tübingen, Germany
| | - M Blak
- Centre of Ophthalmology, University Eye Hospital Tübingen, Elfriede-Aulhorn-Str. 7, D-72076 Tübingen, Germany.,Department of Ophthalmology, Katharinen-Hospital Klinikum Stuttgart, Kriegsbergstr. 60, 70174 Stuttgart, Germany
| | - J Hurst
- Centre of Ophthalmology, University Eye Hospital Tübingen, Elfriede-Aulhorn-Str. 7, D-72076 Tübingen, Germany
| | - T Dorfi
- Centre of Ophthalmology, University Eye Hospital Tübingen, Elfriede-Aulhorn-Str. 7, D-72076 Tübingen, Germany
| | - K U Bartz-Schmidt
- Centre of Ophthalmology, University Eye Hospital Tübingen, Elfriede-Aulhorn-Str. 7, D-72076 Tübingen, Germany
| | - F Ziemssen
- Centre of Ophthalmology, University Eye Hospital Tübingen, Elfriede-Aulhorn-Str. 7, D-72076 Tübingen, Germany
| | - M S Spitzer
- Centre of Ophthalmology, University Eye Hospital Tübingen, Elfriede-Aulhorn-Str. 7, D-72076 Tübingen, Germany.,Department of Ophthalmology, University Medical Center Hamburg-Eppendorf (UKE), Martinistraβe 52, Hamburg, Germany
| | - M Schultheiss
- Centre of Ophthalmology, University Eye Hospital Tübingen, Elfriede-Aulhorn-Str. 7, D-72076 Tübingen, Germany.,Department of Ophthalmology, University Medical Center Hamburg-Eppendorf (UKE), Martinistraβe 52, Hamburg, Germany
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17
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Schnichels S, Dorfi T, Schultheiss M, Arango-Gonzalez B, Bartz-Schmidt KU, Januschowski K, Spitzer MS, Ziemssen F. Ex-vivo-examination of ultrastructural changes in organotypic retina culture using near-infrared imaging and optical coherence tomography. Exp Eye Res 2016; 147:31-36. [PMID: 27109031 DOI: 10.1016/j.exer.2016.04.011] [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: 02/05/2016] [Revised: 04/08/2016] [Accepted: 04/18/2016] [Indexed: 12/27/2022]
Abstract
Optical coherence tomography (OCT) dramatically changed the way of diagnostic assessment in retinal diseases during the last years. Using this technique in-vivo in-depth analysis of the retina and its layers is possible. Since animal research is changing by intrinsic and extrinsic pressure to animal-(in-vivo)-free methods, we adapted OCT-measurements to organotypic cultures. An easy to use protocol was generated to assess standardized OCT assessments in organotypic culture. First, two custom-made devices need to be made to change any commercially available OCT for examinations in humans into a device allowing ex-vivo analyses of organotypic culture. The modification is feasible within seconds. After OCT measurement of the ex-vivo tissues, quantitative evaluation of the retinas were performed via ImageJ software. OCT pictures of ex-vivo retinas were obtained for time periods of seven days and the thickness of retinal tissue was evaluated. The reproducibility of the pictures and measurements was very high (SD < 15%). In conclusion, an easy to use protocol for the investigation of different effects on retinal cultures with commercially available OCT devices was successfully established.
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Affiliation(s)
- Sven Schnichels
- Centre of Ophthalmology, University Eye Hospital Tübingen, Schleichstr. 12/1, D-72076, Tübingen, Germany.
| | - Tanja Dorfi
- Centre of Ophthalmology, University Eye Hospital Tübingen, Schleichstr. 12/1, D-72076, Tübingen, Germany
| | - Maximilian Schultheiss
- Centre of Ophthalmology, University Eye Hospital Tübingen, Schleichstr. 12/1, D-72076, Tübingen, Germany
| | - Blanca Arango-Gonzalez
- Centre of Ophthalmology, Institute for Ophthalmic Research Tübingen, Röntgenweg 11, D-72076, Tübingen, Germany
| | - Karl-Ulrich Bartz-Schmidt
- Centre of Ophthalmology, University Eye Hospital Tübingen, Schleichstr. 12/1, D-72076, Tübingen, Germany
| | - Kai Januschowski
- Centre of Ophthalmology, University Eye Hospital Tübingen, Schleichstr. 12/1, D-72076, Tübingen, Germany; Eye Clinic Sulzbach-Saar, an der Klinik 10, 66111, Sulzbach-Saar, Germany
| | - Martin S Spitzer
- Centre of Ophthalmology, University Eye Hospital Tübingen, Schleichstr. 12/1, D-72076, Tübingen, Germany; Department of Ophthalmology, University Medical Center Hamburg-Eppendorf (UKE), Martinistraße 52, 20251, Hamburg, Germany
| | - Focke Ziemssen
- Centre of Ophthalmology, University Eye Hospital Tübingen, Schleichstr. 12/1, D-72076, Tübingen, Germany
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