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Kaufmann M, Han Z. RPE melanin and its influence on the progression of AMD. Ageing Res Rev 2024; 99:102358. [PMID: 38830546 PMCID: PMC11260545 DOI: 10.1016/j.arr.2024.102358] [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: 02/29/2024] [Accepted: 05/27/2024] [Indexed: 06/05/2024]
Abstract
OBJECTIVE The aim of this review article is to summarize the latest findings and current understanding of the origin of melanin in the retinal pigment epithelium (RPE), its function within the RPE, its role in the pathogenesis of age-related macular degeneration (AMD), its effect on retinal development, and its potential therapeutic benefit in the treatment of AMD. METHODS A comprehensive search of peer-reviewed journals was conducted using various combinations of key terms such as "melanin," "retinal pigment epithelium" or "RPE," "age-related macular degeneration" or AMD," "lipofuscin," "oxidative stress," and "albinism." Databases searched include PubMed, Scopus, Science Direct, and Google Scholar. 147 papers published between the years of 1957 and 2023 were considered with an emphasis on recent findings. SUMMARY OF FINDINGS AMD is thought to result from chronic oxidative stress within the RPE that results in cellular dysfunction, metabolic dysregulation, inflammation, and lipofuscin accumulation. Melanin functions as a photoscreener, free radical scavenger, and metal cation binding reservoir within the RPE. RPE melanin does not regenerate, and it undergoes degradation over time in response to chronic light exposure and oxidative stress. RPE melanin is important for retinal development and RPE function, and in the aging eye, melanin loss is associated with increased lipid peroxidation, inflammation, and the accumulation of toxic oxidized cellular products. Therefore, melanin-based treatments may serve to preserve RPE and retinal function in AMD. CONCLUSIONS The pathogenesis of AMD is not fully understood, but RPE dysfunction and melanin loss in response to chronic oxidative stress and inflammation are thought to be primary drivers of the disease. Due to melanin's antioxidative effects, melanin-based nanotechnology represents a promising avenue for the treatment of AMD.
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Affiliation(s)
- Mary Kaufmann
- University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Zongchao Han
- Department of Ophthalmology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Division of Pharmacoengineering & Molecular Pharmaceutics, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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2
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Ayten M, Díaz-Lezama N, Ghanawi H, Haffelder FC, Kajtna J, Straub T, Borso M, Imhof A, Hauck SM, Koch SF. Metabolic plasticity in a Pde6b STOP/STOP retinitis pigmentosa mouse model following rescue. Mol Metab 2024; 88:101994. [PMID: 39032643 DOI: 10.1016/j.molmet.2024.101994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Revised: 06/18/2024] [Accepted: 07/13/2024] [Indexed: 07/23/2024] Open
Abstract
OBJECTIVE Retinitis pigmentosa (RP) is a hereditary retinal disease characterized by progressive photoreceptor degeneration, leading to vision loss. The best hope for a cure for RP lies in gene therapy. However, given that RP patients are most often diagnosed in the midst of ongoing photoreceptor degeneration, it is unknown how the retinal proteome changes as RP disease progresses, and which changes can be prevented, halted, or reversed by gene therapy. METHODS Here, we used a Pde6b-deficient RP gene therapy mouse model and performed untargeted proteomic analysis to identify changes in protein expression during degeneration and after treatment. RESULTS We demonstrated that Pde6b gene restoration led to a novel form of homeostatic plasticity in rod phototransduction which functionally compensates for the decreased number of rods. By profiling protein levels of metabolic genes and measuring metabolites, we observed an upregulation of proteins associated with oxidative phosphorylation in mutant and treated photoreceptors. CONCLUSION In conclusion, the metabolic demands of the retina differ in our Pde6b-deficient RP mouse model and are not rescued by gene therapy treatment. These findings provide novel insights into features of both RP disease progression and long-term rescue with gene therapy.
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Affiliation(s)
- Monika Ayten
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Nundehui Díaz-Lezama
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Hanaa Ghanawi
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Felia C Haffelder
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Jacqueline Kajtna
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Tobias Straub
- Bioinformatics Unit, Biomedical Center Munich, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Marco Borso
- Molecular Biology, Biomedical Center Munich, Faculty of Medicine, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Axel Imhof
- Molecular Biology, Biomedical Center Munich, Faculty of Medicine, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Stefanie M Hauck
- Metabolomics and Proteomics Core, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Susanne F Koch
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany.
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3
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Chen M, Wang Y, Dalal R, Du J, Vollrath D. Alternative oxidase blunts pseudohypoxia and photoreceptor degeneration due to RPE mitochondrial dysfunction. Proc Natl Acad Sci U S A 2024; 121:e2402384121. [PMID: 38865272 PMCID: PMC11194566 DOI: 10.1073/pnas.2402384121] [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: 02/05/2024] [Accepted: 05/15/2024] [Indexed: 06/14/2024] Open
Abstract
Loss of mitochondrial electron transport complex (ETC) function in the retinal pigment epithelium (RPE) in vivo results in RPE dedifferentiation and progressive photoreceptor degeneration, and has been implicated in the pathogenesis of age-related macular degeneration. Xenogenic expression of alternative oxidases in mammalian cells and tissues mitigates phenotypes arising from some mitochondrial electron transport defects, but can exacerbate others. We expressed an alternative oxidase from Ciona intestinalis (AOX) in ETC-deficient murine RPE in vivo to assess the retinal consequences of stimulating coenzyme Q oxidation and respiration without ATP generation. RPE-restricted expression of AOX in this context is surprisingly beneficial. This focused intervention mitigates RPE mTORC1 activation, dedifferentiation, hypertrophy, stress marker expression, pseudohypoxia, and aerobic glycolysis. These RPE cell autonomous changes are accompanied by increased glucose delivery to photoreceptors with attendant improvements in photoreceptor structure and function. RPE-restricted AOX expression normalizes accumulated levels of succinate and 2-hydroxyglutarate in ETC-deficient RPE, and counteracts deficiencies in numerous neural retinal metabolites. These features can be attributed to the activation of mitochondrial inner membrane flavoproteins such as succinate dehydrogenase and proline dehydrogenase, and alleviation of inhibition of 2-oxyglutarate-dependent dioxygenases such as prolyl hydroxylases and epigenetic modifiers. Our work underscores the importance to outer retinal health of coenzyme Q oxidation in the RPE and identifies a metabolic network critical for photoreceptor survival in the context of RPE mitochondrial dysfunction.
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Affiliation(s)
- Ming Chen
- Department of Genetics, Stanford University School of Medicine, Palo Alto, CA94305
| | - Yekai Wang
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV26506
| | - Roopa Dalal
- Department of Ophthalmology, Stanford University School of Medicine, Palo Alto, CA94305
| | - Jianhai Du
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV26506
| | - Douglas Vollrath
- Department of Genetics, Stanford University School of Medicine, Palo Alto, CA94305
- Department of Ophthalmology, Stanford University School of Medicine, Palo Alto, CA94305
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4
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Xue Y, Cepko CL. Gene Therapies for Retinitis Pigmentosa that Target Glucose Metabolism. Cold Spring Harb Perspect Med 2024; 14:a041289. [PMID: 37460158 PMCID: PMC11065158 DOI: 10.1101/cshperspect.a041289] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2024]
Abstract
Retinitis pigmentosa is a blinding disease wherein rod photoreceptors are affected first, due to the expression of a disease gene, leading to the loss of dim light vision. In many cases, cones do not express the disease gene, yet they are also affected and eventually die, typically after most of the rods in their neighborhood have died. The cause of secondary cone death is unclear. Photoreceptors are one of the most energy-demanding cell types in the body and consume a high amount of glucose. At an early stage of degeneration, the cones appear to have a shortage of glucose to fuel their metabolism. This review focuses on gene therapy approaches that address this potential metabolic shortcoming.
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Affiliation(s)
- Yunlu Xue
- Lingang Laboratory, Shanghai 200031, China
| | - Constance L Cepko
- Departments of Genetics and Ophthalmology, Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
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5
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Menger KE, Logan A, Luhmann UF, Smith AJ, Wright AF, Ali RR, Murphy MP. In vivo measurement of mitochondrial ROS production in mouse models of photoreceptor degeneration. REDOX BIOCHEMISTRY AND CHEMISTRY 2023; 5-6:None. [PMID: 38046619 PMCID: PMC10686909 DOI: 10.1016/j.rbc.2023.100007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 07/18/2023] [Accepted: 07/24/2023] [Indexed: 12/05/2023]
Abstract
Retinitis pigmentosa (RP) is a disease characterised by photoreceptor cell death. It can be initiated by mutations in a number of different genes, primarily affecting rods, which will die first, resulting in loss of night vision. The secondary death of cones then leads to loss of visual acuity and blindness. We set out to investigate whether increased mitochondrial reactive oxygen species (ROS) formation, plays a role in this sequential photoreceptor degeneration. To do this we measured mitochondrial H2O2 production within mouse eyes in vivo using the mass spectrometric probe MitoB. We found higher levels of mitochondrial ROS that preceded photoreceptor loss in four mouse models of RP: Pde6brd1/rd1; Prhp2rds/rds; RPGR-/-; Cln6nclf. In contrast, there was no increase in mitochondrial ROS in loss of function models of vision loss (GNAT-/-, OGC), or where vision loss was not due to photoreceptor death (Cln3). Upregulation of Nrf2 transcriptional activity with dimethylfumarate (DMF) lowered mitochondrial ROS in RPGR-/- mice. These findings have important implications for the mechanism and treatment of RP.
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Affiliation(s)
- Katja E. Menger
- UCL Institute of Ophthalmology, Bath St, London, EC1V 9EL, UK
| | - Angela Logan
- MRC-Mitochondrial Biology Unit, The Keith Peters Building, University of Cambridge, Cambridge, CB2 0XY, UK
| | | | | | - Alan F. Wright
- MRC Human Genetics Unit, Western General Hospital, University of Edinburgh, Edinburgh, EH4 2XU, UK
| | - Robin R. Ali
- UCL Institute of Ophthalmology, Bath St, London, EC1V 9EL, UK
| | - Michael P. Murphy
- MRC-Mitochondrial Biology Unit, The Keith Peters Building, University of Cambridge, Cambridge, CB2 0XY, UK
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6
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Beaver D, Limnios IJ. A treatment within sight: challenges in the development of stem cell-derived photoreceptor therapies for retinal degenerative diseases. FRONTIERS IN TRANSPLANTATION 2023; 2:1130086. [PMID: 38993872 PMCID: PMC11235385 DOI: 10.3389/frtra.2023.1130086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 09/07/2023] [Indexed: 07/13/2024]
Abstract
Stem cell therapies can potentially treat various retinal degenerative diseases, including age-related macular degeneration (AMD) and inherited retinal diseases like retinitis pigmentosa. For these diseases, transplanted cells may include stem cell-derived retinal pigmented epithelial (RPE) cells, photoreceptors, or a combination of both. Although stem cell-derived RPE cells have progressed to human clinical trials, therapies using photoreceptors and other retinal cell types are lagging. In this review, we discuss the potential use of human pluripotent stem cell (hPSC)-derived photoreceptors for the treatment of retinal degeneration and highlight the progress and challenges for their efficient production and clinical application in regenerative medicine.
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Affiliation(s)
- Davinia Beaver
- Clem Jones Centre for Regenerative Medicine, Bond University, Gold Coast, QL, Australia
| | - Ioannis Jason Limnios
- Clem Jones Centre for Regenerative Medicine, Bond University, Gold Coast, QL, Australia
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7
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Lee SJ, Emery D, Vukmanic E, Wang Y, Lu X, Wang W, Fortuny E, James R, Kaplan HJ, Liu Y, Du J, Dean DC. Metabolic transcriptomics dictate responses of cone photoreceptors to retinitis pigmentosa. Cell Rep 2023; 42:113054. [PMID: 37656622 PMCID: PMC10591869 DOI: 10.1016/j.celrep.2023.113054] [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: 05/08/2023] [Revised: 06/21/2023] [Accepted: 08/15/2023] [Indexed: 09/03/2023] Open
Abstract
Most mutations in retinitis pigmentosa (RP) arise in rod photoreceptors, but cone photoreceptors, responsible for high-resolution daylight and color vision, are subsequently affected, causing the most debilitating features of the disease. We used mass spectroscopy to follow 13C metabolites delivered to the outer retina and single-cell RNA sequencing to assess photoreceptor transcriptomes. The S cone metabolic transcriptome suggests engagement of the TCA cycle and ongoing response to ROS characteristic of oxidative phosphorylation, which we link to their histone modification transcriptome. Tumor necrosis factor (TNF) and its downstream effector RIP3, which drive ROS generation via mitochondrial dysfunction, are induced and activated as S cones undergo early apoptosis in RP. The long/medium-wavelength (L/M) cone transcriptome shows enhanced glycolytic capacity, which maintains their function as RP progresses. Then, as extracellular glucose eventually diminishes, L/M cones are sustained in long-term dormancy by lactate metabolism.
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Affiliation(s)
- Sang Joon Lee
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA; Department of Ophthalmology, Kosin University College of Medicine, #262 Gamcheon-ro, Seo-gu, Busan 49267, Korea
| | - Douglas Emery
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Eric Vukmanic
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Yekai Wang
- Departments of Ophthalmology and Visual Sciences and Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506, USA
| | - Xiaoqin Lu
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Wei Wang
- Department of Ophthalmology and Visual Sciences, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Enzo Fortuny
- Department of Neurosurgery, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Robert James
- Department of Neurosurgery, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Henry J Kaplan
- Department of Ophthalmology, St. Louis University School of Medicine, St. Louis MO 63110, USA
| | - Yongqing Liu
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Jianhai Du
- Departments of Ophthalmology and Visual Sciences and Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506, USA.
| | - Douglas C Dean
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA.
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8
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Özkan B, Yılmaz Tuğan B, Hemşinlioğlu C, Sır Karakuş G, Şahin Ö, Ovalı E. Suprachoroidal spheroidal mesenchymal stem cell implantation in retinitis pigmentosa: clinical results of 6 months follow-up. Stem Cell Res Ther 2023; 14:252. [PMID: 37705097 PMCID: PMC10500760 DOI: 10.1186/s13287-023-03489-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Accepted: 09/04/2023] [Indexed: 09/15/2023] Open
Abstract
PURPOSE This prospective clinical case series aimed to evaluate the effect of suprachoroidal implantation of mesenchymal stem cells (MSCs) in the form of spheroids as a stem cell therapy for retinitis pigmentosa (RP) patients with relatively good visual acuity. METHODS Fifteen eyes of 15 patients with RP who received suprachoroidal implantation of MSCs in the form of spheroids were included. Best-corrected visual acuity (BCVA), 10-2 and 30-2 visual field examination and multifocal electroretinography (mfERG) recordings were recorded at baseline, postoperative 1st, 3rd and 6th months during follow-up. RESULTS Baseline median BCVA of RP patients was 1.30 (1.00-2.00) logMAR. BCVA has improved to 1.00 (0.50-1.30), 0.80 (0.40-1.30) and 0.80 (0.40-1.30) at the postoperative 1st, 3rd and 6th months, respectively. The improvements from baseline to the 3rd and 6th months were statistically significant (p = 0.03 and p < 0.001, respectively). In the 30-2 VF test, median MD was significantly improved at the 6th month compared to baseline (p = 0.030). In the 10-2 VF test, the median MD value was significantly different at the 6th month compared to the baseline (p = 0.043). The PSD value of the 10-2 VF test was significantly different at the 6th month compared to the 3rd month (p = 0.043). The amplitudes of P1 waves in < 2°, 5°-10° and 10°-15° rings improved significantly at the postoperative 6th month (p = 0.014, p = 0.018 and p = 0.017, respectively). There was also a statistically significant improvement in implicit times of P1 waves in 10°-15° ring at the postoperative 6th month (p = 0.004). CONCLUSION Suprachoroidal implantation of MSCs in the form of spheroids as a stem cell therapy for RP patients with relatively good visual acuity has an improving effect on BCVA, VF and mfERG recordings during the 6-month follow-up period. Spheroidal MSCs with enhanced effects may be more successful in preventing apoptosis and improving retinal tissue healing in RP patients.
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Affiliation(s)
- Berna Özkan
- Department of Ophthalmology, Acıbadem Mehmet Ali Aydınlar University, Istanbul, Turkey.
| | | | | | | | - Özlem Şahin
- Department of Ophthalmology, Marmara University, Istanbul, Turkey
| | - Ercüment Ovalı
- Acıbadem Labcell Cellular Therapy Center, Istanbul, Turkey
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9
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Weh E, Goswami M, Chaudhury S, Fernando R, Miller N, Hager H, Sheskey S, Sharma V, Wubben TJ, Besirli CG. Metabolic Alterations Caused by Simultaneous Loss of HK2 and PKM2 Leads to Photoreceptor Dysfunction and Degeneration. Cells 2023; 12:2043. [PMID: 37626853 PMCID: PMC10453858 DOI: 10.3390/cells12162043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 08/04/2023] [Accepted: 08/08/2023] [Indexed: 08/27/2023] Open
Abstract
HK2 and PKM2 are two main regulators of aerobic glycolysis. Photoreceptors (PRs) use aerobic glycolysis to produce the biomass necessary for the daily renewal of their outer segments. Previous work has shown that HK2 and PKM2 are important for the normal function and long-term survival of PRs but are dispensable for PR maturation, and their individual loss has opposing effects on PR survival during acute nutrient deprivation. We generated double conditional (dcKO) mice lacking HK2 and PKM2 expression in rod PRs. Western blotting, immunofluorescence, optical coherence tomography, and electroretinography were used to characterize the phenotype of dcKO animals. Targeted and stable isotope tracing metabolomics, qRT-PCR, and retinal oxygen consumption were performed. We show that dcKO animals displayed early shortening of PR inner/outer segments, followed by loss of PRs with aging, much more rapidly than either knockout alone without functional loss as measured by ERG. Significant alterations to central glucose metabolism were observed without any apparent changes to mitochondrial function, prior to PR degeneration. Finally, PR survival following experimental retinal detachment was unchanged in dcKO animals as compared to wild-type animals. These data suggest that HK2 and PKM2 have differing roles in promoting PR neuroprotection and identifying them has important implications for developing therapeutic options for combating PR loss during retinal disease.
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Affiliation(s)
- Eric Weh
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA; (M.G.); (S.C.); (R.F.); (N.M.); (H.H.); (S.S.); (V.S.); (T.J.W.)
| | | | | | | | | | | | | | | | | | - Cagri G. Besirli
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA; (M.G.); (S.C.); (R.F.); (N.M.); (H.H.); (S.S.); (V.S.); (T.J.W.)
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10
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Ellis EM, Paniagua AE, Scalabrino ML, Thapa M, Rathinavelu J, Jiao Y, Williams DS, Field GD, Fain GL, Sampath AP. Cones and cone pathways remain functional in advanced retinal degeneration. Curr Biol 2023; 33:1513-1522.e4. [PMID: 36977418 PMCID: PMC10133175 DOI: 10.1016/j.cub.2023.03.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 12/14/2022] [Accepted: 03/03/2023] [Indexed: 03/29/2023]
Abstract
Most defects causing retinal degeneration in retinitis pigmentosa (RP) are rod-specific mutations, but the subsequent degeneration of cones, which produces loss of daylight vision and high-acuity perception, is the most debilitating feature of the disease. To understand better why cones degenerate and how cone vision might be restored, we have made the first single-cell recordings of light responses from degenerating cones and retinal interneurons after most rods have died and cones have lost their outer-segment disk membranes and synaptic pedicles. We show that degenerating cones have functional cyclic-nucleotide-gated channels and can continue to give light responses, apparently produced by opsin localized either to small areas of organized membrane near the ciliary axoneme or distributed throughout the inner segment. Light responses of second-order horizontal and bipolar cells are less sensitive but otherwise resemble those of normal retina. Furthermore, retinal output as reflected in responses of ganglion cells is less sensitive but maintains spatiotemporal receptive fields at cone-mediated light levels. Together, these findings show that cones and their retinal pathways can remain functional even as degeneration is progressing, an encouraging result for future research aimed at enhancing the light sensitivity of residual cones to restore vision in patients with genetically inherited retinal degeneration.
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Affiliation(s)
- Erika M Ellis
- Department of Ophthalmology and Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA 90095-7000, USA
| | - Antonio E Paniagua
- Department of Ophthalmology and Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA 90095-7000, USA
| | - Miranda L Scalabrino
- Department of Ophthalmology and Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA 90095-7000, USA; Department of Neurobiology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Mishek Thapa
- Department of Ophthalmology and Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA 90095-7000, USA; Department of Neurobiology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Jay Rathinavelu
- Department of Neurobiology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Yuekan Jiao
- Department of Ophthalmology and Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA 90095-7000, USA
| | - David S Williams
- Department of Ophthalmology and Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA 90095-7000, USA.
| | - Greg D Field
- Department of Ophthalmology and Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA 90095-7000, USA; Department of Neurobiology, Duke University School of Medicine, Durham, NC 27710, USA.
| | - Gordon L Fain
- Department of Ophthalmology and Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA 90095-7000, USA.
| | - Alapakkam P Sampath
- Department of Ophthalmology and Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA 90095-7000, USA.
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11
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Song DJ, Bao XL, Fan B, Li GY. Mechanism of Cone Degeneration in Retinitis Pigmentosa. Cell Mol Neurobiol 2023; 43:1037-1048. [PMID: 35792991 DOI: 10.1007/s10571-022-01243-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 06/13/2022] [Indexed: 11/27/2022]
Abstract
Retinitis pigmentosa (RP) is a group of genetic disorders resulting in inherited blindness due to the degeneration of rod and cone photoreceptors. The various mechanisms underlying rod degeneration primarily rely on genetic mutations, leading to night blindness initially. Cones gradually degenerate after rods are almost eliminated, resulting in varying degrees of visual disability and blindness. The mechanism of cone degeneration remains unclear. An understanding of the mechanisms underlying cone degeneration in RP, a highly heterogeneous disease, is essential to develop novel treatments of RP. Herein, we review recent advancements in the five hypotheses of cone degeneration, including oxidative stress, trophic factors, metabolic stress, light damage, and inflammation activation. We also discuss the connection among these theories to provide a better understanding of secondary cone degeneration in RP. Five current mechanisms of cone degenerations in RP Interactions among different pathways are involved in RP.
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Affiliation(s)
- De-Juan Song
- Department of Ophthalmology, The Second Hospital of Jilin University, Changchun, 130000, China
| | - Xiao-Li Bao
- Department of Ophthalmology, The Second Hospital of Jilin University, Changchun, 130000, China
| | - Bin Fan
- Department of Ophthalmology, The Second Hospital of Jilin University, Changchun, 130000, China
| | - Guang-Yu Li
- Department of Ophthalmology, The Second Hospital of Jilin University, Changchun, 130000, China.
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12
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Huynh KT, Walters S, Foley EK, Hunter JJ. Separate lifetime signatures of macaque S cones, M/L cones, and rods observed with adaptive optics fluorescence lifetime ophthalmoscopy. Sci Rep 2023; 13:2456. [PMID: 36774443 PMCID: PMC9922306 DOI: 10.1038/s41598-023-28877-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 01/25/2023] [Indexed: 02/13/2023] Open
Abstract
In the retina, several molecules involved in metabolism, the visual cycle, and other roles exhibit intrinsic fluorescence. The overall properties of retinal fluorescence depend on changes to the composition of these molecules and their environmental interactions due to transient functional shifts, especially in disease. This behooves the understanding of the origins and deviations of these properties within the multilayered retina at high lateral and axial resolution. Of particular interest is the fluorescence lifetime, a potential biomarker of function and disease independent of fluorescence intensity that can be measured in the retina with adaptive optics fluorescence lifetime ophthalmoscopy (AOFLIO). This work demonstrates the utility of the phasor method of analysis, an alternate approach to traditional multiexponential fitting, to evaluate photoreceptor two-photon excited AOFLIO data and separate them based on functional differences. Phasor analysis on fluorescence lifetime decay data allowed the repeatable segregation of S from M/L cones, likely from differences in functional or metabolic demands. Furthermore, it is possible to track the lifetime changes in S cones after photodamage. Phasor analysis increases the sensitivity of AOFLIO to functional differences between cells and has the potential to improve our understanding of pathways involved in normal and diseased conditions at the cellular scale throughout the retina.
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Affiliation(s)
- Khang T Huynh
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA.
- Center for Visual Science, University of Rochester, Rochester, NY, 14642, USA.
| | - Sarah Walters
- Currently with IDEX Health & Science, West Henrietta, NY, 14586, USA
- The Institute of Optics, University of Rochester, Rochester, NY, 14627, USA
| | - Emma K Foley
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA
| | - Jennifer J Hunter
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA
- Center for Visual Science, University of Rochester, Rochester, NY, 14642, USA
- The Institute of Optics, University of Rochester, Rochester, NY, 14627, USA
- Flaum Eye Institute, University of Rochester, Rochester, NY, 14642, USA
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13
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Iker Etchegaray J, Kelley S, Penberthy K, Karvelyte L, Nagasaka Y, Gasperino S, Paul S, Seshadri V, Raymond M, Marco AR, Pinney J, Stremska M, Barron B, Lucas C, Wase N, Fan Y, Unanue E, Kundu B, Burstyn-Cohen T, Perry J, Ambati J, Ravichandran KS. Phagocytosis in the retina promotes local insulin production in the eye. Nat Metab 2023; 5:207-218. [PMID: 36732622 PMCID: PMC10457724 DOI: 10.1038/s42255-022-00728-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 12/16/2022] [Indexed: 02/04/2023]
Abstract
The retina is highly metabolically active, relying on glucose uptake and aerobic glycolysis. Situated in close contact to photoreceptors, a key function of cells in the retinal pigment epithelium (RPE) is phagocytosis of damaged photoreceptor outer segments (POS). Here we identify RPE as a local source of insulin in the eye that is stimulated by POS phagocytosis. We show that Ins2 messenger RNA and insulin protein are produced by RPE cells and that this production correlates with RPE phagocytosis of POS. Genetic deletion of phagocytic receptors ('loss of function') reduces Ins2, whereas increasing the levels of the phagocytic receptor MerTK ('gain of function') increases Ins2 production in male mice. Contrary to pancreas-derived systemic insulin, RPE-derived local insulin is stimulated during starvation, which also increases RPE phagocytosis. Global or RPE-specific Ins2 gene deletion decreases retinal glucose uptake in starved male mice, dysregulates retinal physiology, causes defects in phototransduction and exacerbates photoreceptor loss in a mouse model of retinitis pigmentosa. Collectively, these data identify RPE cells as a phagocytosis-induced local source of insulin in the retina, with the potential to influence retinal physiology and disease.
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Affiliation(s)
- J Iker Etchegaray
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Shannon Kelley
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Kristen Penberthy
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
| | - Laura Karvelyte
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Yosuke Nagasaka
- Center for Advanced Vision Science, University of Virginia, Charlottesville, VA, USA
| | - Sofia Gasperino
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Soumen Paul
- Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, VA, USA
| | - Vikram Seshadri
- Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, VA, USA
| | - Michael Raymond
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
| | - Ana Royo Marco
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
| | - Jonathan Pinney
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
| | - Marta Stremska
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Brady Barron
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Christopher Lucas
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
- University of Edinburgh, Edinburgh, UK
| | - Nishikant Wase
- Biomolecular Analysis Facility, University of Virginia, Charlottesville, VA, USA
| | - Yong Fan
- Drexel University, Philadelphia, PA, USA
| | - Emil Unanue
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Bijoy Kundu
- Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, VA, USA
| | - Tal Burstyn-Cohen
- Hadassah Medical School, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Justin Perry
- Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Jayakrishna Ambati
- Center for Advanced Vision Science, University of Virginia, Charlottesville, VA, USA
- Ophthalmology, University of Virginia, Charlottesville, VA, USA
| | - Kodi S Ravichandran
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA.
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA.
- Hadassah Medical School, Hebrew University of Jerusalem, Jerusalem, Israel.
- VIB/UGent Inflammation Research Centre, and Biomedical Molecular Biology, Ghent University, Ghent, Belgium.
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14
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John MC, Quinn J, Hu ML, Cehajic-Kapetanovic J, Xue K. Gene-agnostic therapeutic approaches for inherited retinal degenerations. Front Mol Neurosci 2023; 15:1068185. [PMID: 36710928 PMCID: PMC9881597 DOI: 10.3389/fnmol.2022.1068185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Accepted: 12/12/2022] [Indexed: 01/11/2023] Open
Abstract
Inherited retinal diseases (IRDs) are associated with mutations in over 250 genes and represent a major cause of irreversible blindness worldwide. While gene augmentation or gene editing therapies could address the underlying genetic mutations in a small subset of patients, their utility remains limited by the great genetic heterogeneity of IRDs and the costs of developing individualised therapies. Gene-agnostic therapeutic approaches target common pathogenic pathways that drive retinal degeneration or provide functional rescue of vision independent of the genetic cause, thus offering potential clinical benefits to all IRD patients. Here, we review the key gene-agnostic approaches, including retinal cell reprogramming and replacement, neurotrophic support, immune modulation and optogenetics. The relative benefits and limitations of these strategies and the timing of clinical interventions are discussed.
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Affiliation(s)
- Molly C. John
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Joel Quinn
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Monica L. Hu
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Jasmina Cehajic-Kapetanovic
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom
| | - Kanmin Xue
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom
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15
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Xue Y. Txnip Gene Therapy of Retinitis Pigmentosa Improves Cone Health. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1415:143-146. [PMID: 37440027 DOI: 10.1007/978-3-031-27681-1_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
Retinitis pigmentosa (RP) is a hereditary retinal degenerative disease that can lead to blindness. In RP, rod photoreceptors die first, followed by cone photoreceptors death due to unknown mechanisms. However, one clue for cone death concerns their metabolism. Early changes suggest that they do not have enough glucose, which normally fuels their metabolism. We sought to design adeno-associated virus (AAV)-based gene therapy to address their metabolic challenges and found that overexpressing Txnip is an effective gene therapy that extends cone survival and vision in three strains of RP mice. The Txnip-mediated rescue was found to be dependent upon lactate dehydrogenase b (Ldhb), which is required for lactate catabolism. Txnip also was found to improve mitochondrial health. Herein, we propose a model in which Txnip shifts cones from their normal reliance on glucose to enhanced utilization of lactate to benefit cones in a condition where the glucose supply is limiting.
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Affiliation(s)
- Yunlu Xue
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
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16
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Das A, Imanishi Y. Drug Discovery Strategies for Inherited Retinal Degenerations. BIOLOGY 2022; 11:1338. [PMID: 36138817 PMCID: PMC9495580 DOI: 10.3390/biology11091338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 08/31/2022] [Accepted: 09/07/2022] [Indexed: 12/03/2022]
Abstract
Inherited retinal degeneration is a group of blinding disorders afflicting more than 1 in 4000 worldwide. These disorders frequently cause the death of photoreceptor cells or retinal ganglion cells. In a subset of these disorders, photoreceptor cell death is a secondary consequence of retinal pigment epithelial cell dysfunction or degeneration. This manuscript reviews current efforts in identifying targets and developing small molecule-based therapies for these devastating neuronal degenerations, for which no cures exist. Photoreceptors and retinal ganglion cells are metabolically demanding owing to their unique structures and functional properties. Modulations of metabolic pathways, which are disrupted in most inherited retinal degenerations, serve as promising therapeutic strategies. In monogenic disorders, great insights were previously obtained regarding targets associated with the defective pathways, including phototransduction, visual cycle, and mitophagy. In addition to these target-based drug discoveries, we will discuss how phenotypic screening can be harnessed to discover beneficial molecules without prior knowledge of their mechanisms of action. Because of major anatomical and biological differences, it has frequently been challenging to model human inherited retinal degeneration conditions using small animals such as rodents. Recent advances in stem cell-based techniques are opening new avenues to obtain pure populations of human retinal ganglion cells and retinal organoids with photoreceptor cells. We will discuss concurrent ideas of utilizing stem-cell-based disease models for drug discovery and preclinical development.
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Affiliation(s)
- Arupratan Das
- Department of Ophthalmology, Eugene and Marilyn Glick Eye Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Yoshikazu Imanishi
- Department of Ophthalmology, Eugene and Marilyn Glick Eye Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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17
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Daniele LL, Han JYS, Samuels IS, Komirisetty R, Mehta N, McCord JL, Yu M, Wang Y, Boesze-Battaglia K, Bell BA, Du J, Peachey NS, Philp NJ. Glucose uptake by GLUT1 in photoreceptors is essential for outer segment renewal and rod photoreceptor survival. FASEB J 2022; 36:e22428. [PMID: 35766190 PMCID: PMC9438481 DOI: 10.1096/fj.202200369r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 05/27/2022] [Accepted: 06/10/2022] [Indexed: 02/07/2023]
Abstract
Photoreceptors consume glucose supplied by the choriocapillaris to support phototransduction and outer segment (OS) renewal. Reduced glucose supply underlies photoreceptor cell death in inherited retinal degeneration and age-related retinal disease. We have previously shown that restricting glucose transport into the outer retina by conditional deletion of Slc2a1 encoding GLUT1 resulted in photoreceptor loss and impaired OS renewal. However, retinal neurons, glia, and the retinal pigment epithelium play specialized, synergistic roles in metabolite supply and exchange, and the cell-specific map of glucose uptake and utilization in the retina is incomplete. In these studies, we conditionally deleted Slc2a1 in a pan-retinal or rod-specific manner to better understand how glucose is utilized in the retina. Using non-invasive ocular imaging, electroretinography, and histochemical and biochemical analyses we show that genetic deletion of Slc2a1 from retinal neurons and Müller glia results in reduced OS growth and progressive rod but not cone photoreceptor cell death. Rhodopsin levels were severely decreased even at postnatal day 20 when OS length was relatively normal. Arrestin levels were not changed suggesting that glucose uptake is required to synthesize membrane glycoproteins. Rod-specific deletion of Slc2a1 resulted in similar changes in OS length and rod photoreceptor cell death. These studies demonstrate that glucose is an essential carbon source for rod photoreceptor cell OS maintenance and viability.
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Affiliation(s)
- Lauren L Daniele
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - John Y S Han
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Ivy S Samuels
- Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA.,Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio, USA
| | - Ravikiran Komirisetty
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Nikhil Mehta
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Jessica L McCord
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Minzhong Yu
- Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA.,Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio, USA
| | - Yekai Wang
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA.,Department of Biochemistry, West Virginia University, Morgantown, West Virginia, USA
| | - Kathleen Boesze-Battaglia
- Department of Basic and Translational Sciences, Penn Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Brent A Bell
- Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Jianhai Du
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA.,Department of Biochemistry, West Virginia University, Morgantown, West Virginia, USA
| | - Neal S Peachey
- Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA.,Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio, USA.,Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio, USA
| | - Nancy J Philp
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
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18
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Gene-independent therapeutic interventions to maintain and restore light sensitivity in degenerating photoreceptors. Prog Retin Eye Res 2022; 90:101065. [PMID: 35562270 DOI: 10.1016/j.preteyeres.2022.101065] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 04/08/2022] [Accepted: 04/18/2022] [Indexed: 12/14/2022]
Abstract
Neurodegenerative retinal diseases are a prime cause of blindness in industrialized countries. In many cases, there are no therapeutic treatments, although they are essential to improve patients' quality of life. A set of disease-causing genes, which primarily affect photoreceptors, has already been identified and is of major interest for developing gene therapies. Nevertheless, depending on the nature and the state of the disease, gene-independent strategies are needed. Various strategies to halt disease progression or maintain function of the retina are under research. These therapeutic interventions include neuroprotection, direct reprogramming of affected photoreceptors, the application of non-coding RNAs, the generation of artificial photoreceptors by optogenetics and cell replacement strategies. During recent years, major breakthroughs have been made such as the first optogenetic application to a blind patient whose visual function partially recovered by targeting retinal ganglion cells. Also, RPE cell transplantation therapies are under clinical investigation and show great promise to improve visual function in blind patients. These cells are generated from human stem cells. Similar therapies for replacing photoreceptors are extensively tested in pre-clinical models. This marks just the start of promising new cures taking advantage of developments in the areas of genetic engineering, optogenetics, and stem-cell research. In this review, we present the recent therapeutic advances of gene-independent approaches that are currently under clinical evaluation. Our main focus is on photoreceptors as these sensory cells are highly vulnerable to degenerative diseases, and are crucial for light detection.
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19
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Kanan Y, Hackett SF, Taneja K, Khan M, Campochiaro PA. Oxidative stress-induced alterations in retinal glucose metabolism in Retinitis Pigmentosa. Free Radic Biol Med 2022; 181:143-153. [PMID: 35134532 PMCID: PMC8891093 DOI: 10.1016/j.freeradbiomed.2022.01.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2021] [Revised: 01/21/2022] [Accepted: 01/31/2022] [Indexed: 10/19/2022]
Abstract
Retinitis pigmentosa occurs due to mutations that cause rod photoreceptor degeneration. Once most rods are lost, gradual degeneration of cone photoreceptors occurs. Oxidative damage and abnormal glucose metabolism have been implicated as contributors to cone photoreceptor death. Herein, we show increased phosphorylation of key enzymes of glucose metabolism in the retinas of rd10 mice, a model of RP, and retinas of wild type mice with paraquat-induced oxidative stress, thereby inhibiting these key enzymes. Dietary supplementation with glucose and pyruvate failed to overcome the inhibition, but increased reducing equivalents in the retina and improved cone function and survival. Dichloroacetate reversed the increased phosphorylation of pyruvate dehydrogenase in rd10 retina and increased histone acetylation and levels of TP53-induced glycolysis and apoptosis regulator (TIGAR), which redirected glucose metabolism toward the pentose phosphate pathway. These data indicate that oxidative stress induced damage can be reversed by shifting glycolytic intermediates toward the pentose phosphate pathway which increases reducing equivalents and provides photoreceptor protection.
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Affiliation(s)
- Yogita Kanan
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Sean F Hackett
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Kamil Taneja
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Mahmood Khan
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Peter A Campochiaro
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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20
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Insights into pathological mechanisms and interventions revealed by analyzing a mathematical model for cone metabolism. Biosci Rep 2022; 42:230791. [PMID: 35156683 PMCID: PMC8905305 DOI: 10.1042/bsr20212457] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 01/14/2022] [Accepted: 02/11/2022] [Indexed: 11/17/2022] Open
Abstract
This work analyzes a mathematical model for the metabolic dynamics of a cone photoreceptor, which is the first model to account for energy generation from fatty acids oxidation of shed photoreceptor outer segments (POS). Multiple parameter bifurcation analysis shows that joint variations in external glucose, the efficiency of glucose transporter 1 (GLUT1), lipid utilization for POS renewal, and oxidation of fatty acids affect the cone’s metabolic vitality and its capability to adapt under glucose-deficient conditions. The analysis further reveals that when glucose is scarce, cone viability cannot be sustained by only fueling energy production in the mitochondria, but it also requires supporting anabolic processes to create lipids necessary for cell maintenance and repair. In silico experiments are used to investigate how the duration of glucose deprivation impacts the cell without and with a potential GLUT1 or oxidation of fatty acids intervention as well as a dual intervention. The results show that for prolonged duration of glucose deprivation, the cone metabolic system does not recover with higher oxidation of fatty acids and requires greater effectiveness of GLUT1 to recover. Finally, time-varying global sensitivity analysis (GSA) is applied to assess the sensitivity of the model outputs of interest to changes and uncertainty in the parameters at specific times. The results reveal a critical temporal window where there would be more flexibility for interventions to rescue a cone cell from the detrimental consequences of glucose shortage.
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21
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Zeviani M, Carelli V. Mitochondrial Retinopathies. Int J Mol Sci 2021; 23:210. [PMID: 35008635 PMCID: PMC8745158 DOI: 10.3390/ijms23010210] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 12/14/2021] [Accepted: 12/18/2021] [Indexed: 12/13/2022] Open
Abstract
The retina is an exquisite target for defects of oxidative phosphorylation (OXPHOS) associated with mitochondrial impairment. Retinal involvement occurs in two ways, retinal dystrophy (retinitis pigmentosa) and subacute or chronic optic atrophy, which are the most common clinical entities. Both can present as isolated or virtually exclusive conditions, or as part of more complex, frequently multisystem syndromes. In most cases, mutations of mtDNA have been found in association with mitochondrial retinopathy. The main genetic abnormalities of mtDNA include mutations associated with neurogenic muscle weakness, ataxia and retinitis pigmentosa (NARP) sometimes with earlier onset and increased severity (maternally inherited Leigh syndrome, MILS), single large-scale deletions determining Kearns-Sayre syndrome (KSS, of which retinal dystrophy is a cardinal symptom), and mutations, particularly in mtDNA-encoded ND genes, associated with Leber hereditary optic neuropathy (LHON). However, mutations in nuclear genes can also cause mitochondrial retinopathy, including autosomal recessive phenocopies of LHON, and slowly progressive optic atrophy caused by dominant or, more rarely, recessive, mutations in the fusion/mitochondrial shaping protein OPA1, encoded by a nuclear gene on chromosome 3q29.
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Affiliation(s)
- Massimo Zeviani
- Department of Neurosciences, The Clinical School, University of Padova, 35128 Padova, Italy
- Veneto Institute of Molecular Medicine, Via Orus 2, 35128 Padova, Italy
| | - Valerio Carelli
- Department of Biomedical and Neuromotor Sciences, University of Bologna, 40139 Bologna, Italy
- Programma di Neurogenetica, IRCCS Istituto delle Scienze Neurologiche di Bologna, Via Altura 6, 40139 Bologna, Italy
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22
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Patel SN, Mahmoud TH, Kazahaya M, Todorich B. AUTOLOGOUS NEUROSENSORY RETINAL TRANSPLANTATION: Bridging the Gap. Retina 2021; 41:2417-2423. [PMID: 33990116 DOI: 10.1097/iae.0000000000003210] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE To review the autologous retinal transplantation surgical technique, indications, rationale, and current outcomes of data published to date. METHODS Review of surgical technique, preoperative and postoperative best-corrected visual acuity, and macular hole (MH) closure rate in studies with at least five eyes. RESULTS The weighted average macular hole closure rate is 88%, with a MH closure rate ranging from 66.7% to 100%. The weighted average best-corrected visual acuity improved from mean logarithm of the minimum angle of resolution 1.35 (Snellen equivalent of 20/450) preoperatively to mean logarithm of the minimum angle of resolution 1.02 (Snellen equivalent of 20/210) postoperatively. From the largest autologous retinal transplantation case series, 37% of patients gained 3 or more lines of visual acuity after autologous retinal transplantation for primary or refractory MHs and 74% gained 3 or more lines of visual acuity after autologous retinal transplantation for MH-retinal detachments. Functional improvement including negative Watzke-Allen sign and conversion from positive to negative scotoma was reported in large case series. CONCLUSION Autologous retinal transplantation is a promising technique for closure of large and refractory MHs otherwise difficult to repair with conventional techniques. This technique may allow for replacement of neural tissue in the macula through cell rehabilitation and regeneration through presumed ectopic synaptogenesis, retinal progenitor cell differentiation and integration, and/or retinal progenitor cell material transfer to host neurons.
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Affiliation(s)
- Saagar N Patel
- Department of Ophthalmology, Penn State College of Medicine, Hershey, Pennsylvania
| | - Tamer H Mahmoud
- Associated Retinal Consultants, William Beaumont Hospital, Royal Oak, Michigan; and
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23
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Greco JA, Wagner NL, Jensen RJ, Lawrence DB, Ranaghan MJ, Sandberg MN, Sandberg DJ, Birge RR. Activation of retinal ganglion cells using a biomimetic artificial retina. J Neural Eng 2021; 18. [PMID: 34768254 DOI: 10.1088/1741-2552/ac395c] [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: 05/26/2021] [Accepted: 11/12/2021] [Indexed: 11/12/2022]
Abstract
Objective.Biomimetic protein-based artificial retinas offer a new paradigm for restoring vision for patients blinded by retinal degeneration. Artificial retinas, comprised of an ion-permeable membrane and alternating layers of bacteriorhodopsin (BR) and a polycation binder, are assembled using layer-by-layer electrostatic adsorption. Upon light absorption, the oriented BR layers generate a unidirectional proton gradient. The main objective of this investigation is to demonstrate the ability of the ion-mediated subretinal artificial retina to activate retinal ganglion cells (RGCs) of degenerated retinal tissue.Approach. Ex vivoextracellular recording experiments with P23H line 1 rats are used to measure the response of RGCs following selective stimulation of our artificial retina using a pulsed light source. Single-unit recording is used to evaluate the efficiency and latency of activation, while a multielectrode array (MEA) is used to assess the spatial sensitivity of the artificial retina films.Main results.The activation efficiency of the artificial retina increases with increased incident light intensity and demonstrates an activation latency of ∼150 ms. The results suggest that the implant is most efficient with 200 BR layers and can stimulate the retina using light intensities comparable to indoor ambient light. Results from using an MEA show that activation is limited to the targeted receptive field.Significance.The results of this study establish potential effectiveness of using an ion-mediated artificial retina to restore vision for those with degenerative retinal diseases, including retinitis pigmentosa.
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Affiliation(s)
- Jordan A Greco
- Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, CT 06269, United States of America
| | - Nicole L Wagner
- Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, CT 06269, United States of America.,Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, CT 06269, United States of America
| | - Ralph J Jensen
- VA Boston Healthcare System, 150 South Huntington Avenue, Boston, MA 02130, United States of America
| | - Daniel B Lawrence
- University of Connecticut School of Medicine, 263 Farmington Avenue, Farmington, CT 06032, United States of America
| | - Matthew J Ranaghan
- Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, CT 06269, United States of America
| | - Megan N Sandberg
- Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, CT 06269, United States of America
| | - Daniel J Sandberg
- Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, CT 06269, United States of America
| | - Robert R Birge
- Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, CT 06269, United States of America.,Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, CT 06269, United States of America
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24
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Ortin‐Martinez A, Yan NE, Tsai ELS, Comanita L, Gurdita A, Tachibana N, Liu ZC, Lu S, Dolati P, Pokrajac NT, El‐Sehemy A, Nickerson PEB, Schuurmans C, Bremner R, Wallace VA. Photoreceptor nanotubes mediate the in vivo exchange of intracellular material. EMBO J 2021; 40:e107264. [PMID: 34494680 PMCID: PMC8591540 DOI: 10.15252/embj.2020107264] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 07/15/2021] [Accepted: 07/19/2021] [Indexed: 12/17/2022] Open
Abstract
Emerging evidence suggests that intracellular molecules and organelles transfer between cells during embryonic development, tissue homeostasis and disease. We and others recently showed that transplanted and host photoreceptors engage in bidirectional transfer of intracellular material in the recipient retina, a process termed material transfer (MT). We used cell transplantation, advanced tissue imaging approaches, genetic and pharmacologic interventions and primary cell culture to characterize and elucidate the mechanism of MT. We show that MT correlates with donor cell persistence and the accumulation of donor-derived proteins, mitochondria and transcripts in acceptor cells in vivo. MT requires cell contact in vitro and is associated with the formation of stable microtubule-containing protrusions, termed photoreceptor nanotubes (Ph NTs), that connect donor and host cells in vivo and in vitro. Ph NTs mediate GFP transfer between connected cells in vitro. Furthermore, interfering with Ph NT outgrowth by targeting Rho GTPase-dependent actin remodelling inhibits MT in vivo. Collectively, our observations provide evidence for horizontal exchange of intracellular material via nanotube-like connections between neurons in vivo.
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Affiliation(s)
- Arturo Ortin‐Martinez
- Donald K. Johnson Eye InstituteKrembil Research InstituteUniversity Health NetworkTorontoONCanada
| | - Nicole E Yan
- Donald K. Johnson Eye InstituteKrembil Research InstituteUniversity Health NetworkTorontoONCanada
- Department of Laboratory Medicine and PathobiologyUniversity of TorontoTorontoONCanada
| | - En Leh Samuel Tsai
- Donald K. Johnson Eye InstituteKrembil Research InstituteUniversity Health NetworkTorontoONCanada
| | - Lacrimioara Comanita
- Donald K. Johnson Eye InstituteKrembil Research InstituteUniversity Health NetworkTorontoONCanada
| | - Akshay Gurdita
- Donald K. Johnson Eye InstituteKrembil Research InstituteUniversity Health NetworkTorontoONCanada
- Department of Laboratory Medicine and PathobiologyUniversity of TorontoTorontoONCanada
| | - Nobuhiko Tachibana
- Donald K. Johnson Eye InstituteKrembil Research InstituteUniversity Health NetworkTorontoONCanada
| | - Zhongda C Liu
- Donald K. Johnson Eye InstituteKrembil Research InstituteUniversity Health NetworkTorontoONCanada
| | - Suying Lu
- Lunenfeld Tanenbaum Research InstituteMount Sinai HospitalSinai Health SystemsTorontoONCanada
| | - Parnian Dolati
- Donald K. Johnson Eye InstituteKrembil Research InstituteUniversity Health NetworkTorontoONCanada
- Department of Laboratory Medicine and PathobiologyUniversity of TorontoTorontoONCanada
| | - Neno T Pokrajac
- Donald K. Johnson Eye InstituteKrembil Research InstituteUniversity Health NetworkTorontoONCanada
- Department of Laboratory Medicine and PathobiologyUniversity of TorontoTorontoONCanada
| | - Ahmed El‐Sehemy
- Donald K. Johnson Eye InstituteKrembil Research InstituteUniversity Health NetworkTorontoONCanada
- Department of Laboratory Medicine and PathobiologyUniversity of TorontoTorontoONCanada
| | - Philip E B Nickerson
- Donald K. Johnson Eye InstituteKrembil Research InstituteUniversity Health NetworkTorontoONCanada
| | - Carol Schuurmans
- Department of Laboratory Medicine and PathobiologyUniversity of TorontoTorontoONCanada
- Department of BiochemistryUniversity of TorontoTorontoONCanada
- Sunnybrook Research InstituteTorontoONCanada
- Department of Ophthalmology and Vision SciencesUniversity of TorontoTorontoONCanada
| | - Rod Bremner
- Department of Laboratory Medicine and PathobiologyUniversity of TorontoTorontoONCanada
- Lunenfeld Tanenbaum Research InstituteMount Sinai HospitalSinai Health SystemsTorontoONCanada
- Department of Ophthalmology and Vision SciencesUniversity of TorontoTorontoONCanada
| | - Valerie A Wallace
- Donald K. Johnson Eye InstituteKrembil Research InstituteUniversity Health NetworkTorontoONCanada
- Department of Laboratory Medicine and PathobiologyUniversity of TorontoTorontoONCanada
- Department of Ophthalmology and Vision SciencesUniversity of TorontoTorontoONCanada
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25
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Kaplan HJ. Innovations in retinitis pigmentosa - Metabolic rescue of cones, gene therapy, retinal transplantation. Taiwan J Ophthalmol 2021; 11:329-330. [PMID: 35070659 PMCID: PMC8757524 DOI: 10.4103/tjo.tjo_50_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2021] [Accepted: 10/24/2021] [Indexed: 11/17/2022] Open
Affiliation(s)
- Henry J Kaplan
- Department of Ophthalmology, Saint Louis University School of Medicine, Saint Louis, Missouri, USA
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26
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Kaplan HJ, Wang W, Piri N, Dean DC. Metabolic rescue of cone photoreceptors in retinitis pigmentosa. Taiwan J Ophthalmol 2021; 11:331-335. [PMID: 35070660 PMCID: PMC8757513 DOI: 10.4103/tjo.tjo_46_21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2021] [Accepted: 10/05/2021] [Indexed: 12/27/2022] Open
Abstract
Retinitis pigmentosa (RP) encompasses a group of inherited retinal dystrophies characterized by the primary degeneration of rod and cone photoreceptors. It is a leading cause of visual disability, with an incidence of ~1 in 7000 persons. Although most RP is nonsyndromic, 20%-30% of patients with RP also have an associated nonocular condition. The gene mutations responsible for RP occur overwhelmingly in rod photoreceptors. Visual loss frequently begins with night blindness in adolescence, followed by concentric visual field loss, reflecting the principal dysfunction of rod photoreceptors. Although the visual disability from rod dysfunction is significant, it is the subsequent loss of central vision later in life due to cone degeneration that is catastrophic. Until recently, the reason for cone dysfunction in RP was unknown. However, it is now recognized that cones degenerate, losing outer segment (OS) synthesis and inner segment (IS) disassembly because of glucose starvation following rod demise. Rod OS phagocytosis by the apical microvilli of retinal pigment epithelium is necessary to transport glucose from the choriocapillaris to the subretinal space. Although cones lose OS with the onset of rod degeneration in RP, regardless of the gene mutation in rods, cone nuclei remain viable for years (i.e. enter cone dormancy) so that therapies aimed at reversing glucose starvation can prevent and/or recover cone function and central vision.
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Affiliation(s)
- Henry J Kaplan
- Department of Ophthalmology, Saint Louis University School of Medicine, Saint Louis, Missouri, USA
| | - Wei Wang
- Department of Ophthalmology and Visual Sciences, University of Louisville Health Sciences Center, Louisville, Kentucky, USA
| | - Niloofar Piri
- Department of Ophthalmology, Saint Louis University School of Medicine, Saint Louis, Missouri, USA
| | - Douglas C Dean
- Department of Medicine, University of Louisville Health Sciences Center, Louisville, Kentucky, USA
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27
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Bereimipour A, Najafi H, Mirsane ES, Moradi S, Satarian L. Roles of miR-204 in retinal development and maintenance. Exp Cell Res 2021; 406:112737. [PMID: 34324864 DOI: 10.1016/j.yexcr.2021.112737] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Revised: 07/05/2021] [Accepted: 07/07/2021] [Indexed: 12/14/2022]
Abstract
The retina is the innermost part of the eye of most vertebrates and it is essential for vision. The development, maintenance, and function of this laminated structure is tightly regulated by numerous genes. Deficiencies in the expression of these genes as well as deregulation of various molecular mechanisms can cause retinopathies and blindness. MicroRNAs (miRNAs) are one of the most important and effective molecular regulatory mechanisms that underlie the biology of the retina. miRNAs have specific functional roles in the development and maintenance of different retinal layers and retinal cell types. While previous studies have reported a large number of miRNAs linked to development, maintenance and diseases of the retina, no comprehensive study has properly discussed and integrated data from these studies. Given the particular importance of miR-204 in retinal biology, we intend to critically discuss the expression and functional significance of this miRNA in the development, maintenance, and pathologies of the retina. Moreover, we explore biological processes through which miR-204 influences retinal pathophysiology. This review highlights the crucial functions of miR-204 in the retina and suggests the putative mechanism of miR-204 action in retinal biology.
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Affiliation(s)
- Ahmad Bereimipour
- Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran; Faculty of Sciences and Advanced Technologies in Biology, University of Science and Culture, Tehran, Iran
| | - Hadi Najafi
- Department of Genetics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
| | - Elahe Sadat Mirsane
- Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran
| | - Sharif Moradi
- Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran.
| | - Leila Satarian
- Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran.
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28
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Abstract
Inherited retinal diseases (IRDs) are an important cause of blindness worldwide. Over 270 genes have been associated with IRD. Genetic testing can determine the cause of the clinical disease in the majority of patients. However, at least 25-50% of patients with clinical diagnosis of IRD remain unsolved even after whole genome sequencing. Animal models of IRD can be useful for expanding the set of established IRD genes, to gain biological understanding of the function of these genes in the retina, and to test advanced therapeutics prior to human clinical trials. In this chapter some small and large animal models of IRD are discussed including some of the advantages and limitations of each for various forms of retinopathy.
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29
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Abstract
The outer retina is nourished from the choroid, a capillary bed just inside the sclera. O2, glucose, and other nutrients diffuse out of the choroid and then filter through a monolayer of retinal pigment epithelium (RPE) cells to fuel the retina. Recent studies of energy metabolism have revealed striking differences between retinas and RPE cells in the ways that they extract energy from fuels. The purpose of this review is to suggest and evaluate the hypothesis that the retina and RPE have complementary metabolic roles that make them depend on each other for survival and for their abilities to perform essential and specialized functions. Expected final online publication date for the Annual Review of Vision Science, Volume 7 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- James B Hurley
- Departments of Biochemistry and Ophthalmology, University of Washington, Seattle, Washington 98115, USA;
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30
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Viegas FO, Neuhauss SCF. A Metabolic Landscape for Maintaining Retina Integrity and Function. Front Mol Neurosci 2021; 14:656000. [PMID: 33935647 PMCID: PMC8081888 DOI: 10.3389/fnmol.2021.656000] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 03/22/2021] [Indexed: 01/27/2023] Open
Abstract
Neurons have high metabolic demands that are almost exclusively met by glucose supplied from the bloodstream. Glucose is utilized in complex metabolic interactions between neurons and glia cells, described by the astrocyte-neuron lactate shuttle (ANLS) hypothesis. The neural retina faces similar energy demands to the rest of the brain, with additional high anabolic needs to support continuous renewal of photoreceptor outer segments. This demand is met by a fascinating variation of the ANLS in which photoreceptors are the central part of a metabolic landscape, using glucose and supplying surrounding cells with metabolic intermediates. In this review we summarize recent evidence on how neurons, in particular photoreceptors, meet their energy and biosynthetic requirements by comprising a metabolic landscape of interdependent cells.
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Affiliation(s)
- Filipe O Viegas
- Department of Molecular Life Sciences, University of Zurich, Zurich, Switzerland.,Life Science Zurich Graduate School, Ph.D. Program in Molecular Life Sciences, Zurich, Switzerland
| | - Stephan C F Neuhauss
- Department of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
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31
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Xue Y, Wang SK, Rana P, West ER, Hong CM, Feng H, Wu DM, Cepko CL. AAV-Txnip prolongs cone survival and vision in mouse models of retinitis pigmentosa. eLife 2021; 10:e66240. [PMID: 33847261 PMCID: PMC8081528 DOI: 10.7554/elife.66240] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 03/30/2021] [Indexed: 01/14/2023] Open
Abstract
Retinitis pigmentosa (RP) is an inherited retinal disease affecting >20 million people worldwide. Loss of daylight vision typically occurs due to the dysfunction/loss of cone photoreceptors, the cell type that initiates our color and high-acuity vision. Currently, there is no effective treatment for RP, other than gene therapy for a limited number of specific disease genes. To develop a disease gene-agnostic therapy, we screened 20 genes for their ability to prolong cone photoreceptor survival in vivo. Here, we report an adeno-associated virus vector expressing Txnip, which prolongs the survival of cone photoreceptors and improves visual acuity in RP mouse models. A Txnip allele, C247S, which blocks the association of Txnip with thioredoxin, provides an even greater benefit. Additionally, the rescue effect of Txnip depends on lactate dehydrogenase b (Ldhb) and correlates with the presence of healthier mitochondria, suggesting that Txnip saves RP cones by enhancing their lactate catabolism.
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Affiliation(s)
- Yunlu Xue
- Department of Genetics, Blavatnik Institute, Harvard Medical SchoolBostonUnited States
- Department of Ophthalmology, Harvard Medical SchoolBostonUnited States
| | - Sean K Wang
- Department of Genetics, Blavatnik Institute, Harvard Medical SchoolBostonUnited States
- Department of Ophthalmology, Harvard Medical SchoolBostonUnited States
- Howard Hughs Medical InstituteChevy ChaseUnited States
| | - Parimal Rana
- Department of Genetics, Blavatnik Institute, Harvard Medical SchoolBostonUnited States
| | - Emma R West
- Department of Genetics, Blavatnik Institute, Harvard Medical SchoolBostonUnited States
- Howard Hughs Medical InstituteChevy ChaseUnited States
| | - Christin M Hong
- Department of Genetics, Blavatnik Institute, Harvard Medical SchoolBostonUnited States
- Howard Hughs Medical InstituteChevy ChaseUnited States
| | - Helian Feng
- Department of Biostatistics, Harvard T.H. Chan School of Public HealthBostonUnited States
| | - David M Wu
- Department of Genetics, Blavatnik Institute, Harvard Medical SchoolBostonUnited States
- Department of Ophthalmology, Harvard Medical SchoolBostonUnited States
- Retina Service, Massachusetts Eye and Ear Infirmary, Harvard Medical SchoolBostonUnited States
| | - Constance L Cepko
- Department of Genetics, Blavatnik Institute, Harvard Medical SchoolBostonUnited States
- Department of Ophthalmology, Harvard Medical SchoolBostonUnited States
- Howard Hughs Medical InstituteChevy ChaseUnited States
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32
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Sahli E, Arslan U, Özmert E, İdil A. Evaluation of the effect of subtenon autologous platelet-rich plasma injections on visual functions in patients with retinitis pigmentosa. Regen Med 2021; 16:131-143. [PMID: 33754798 DOI: 10.2217/rme-2020-0075] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Aim: The photoreceptors in retinitis pigmentosa (RP) remain in dormant status for a while with a decrease in the growth factors in their microenvironment before apoptosis. Growth factors reduce retinal degeneration and apoptosis in animal models. Materials & methods: The data of 188 eyes of 94 patients who were injected with autologous platelet-rich plasma (PRP) into the subtenon space three-times every 2 weeks were evaluated retrospectively. Results: Statistically significant improvements in visual acuity, visual field and fixation stability were detected after treatment. When the treatment response of the patients' better-seeing eye compared with the response of the other eye, there was no statistically significant difference. Conclusion: The PRP treatment has a favorable effect on visual functions in patients with RP. This approach is promising as it is safe and easy.
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Affiliation(s)
- Esra Sahli
- Department of Ophthalmology, Ankara University, School of Medicine, Ankara 06620, Turkey
| | - Umut Arslan
- Ankara University, Technopolis, Ankara 06830, Turkey.,Bioretina Eye Clinic, Ankara 06560, Turkey
| | - Emin Özmert
- Department of Ophthalmology, Ankara University, School of Medicine, Ankara 06620, Turkey
| | - Aysun İdil
- Department of Ophthalmology, Ankara University, School of Medicine, Ankara 06620, Turkey
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33
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Light responses of mammalian cones. Pflugers Arch 2021; 473:1555-1568. [PMID: 33742309 DOI: 10.1007/s00424-021-02551-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 02/28/2021] [Accepted: 03/03/2021] [Indexed: 12/24/2022]
Abstract
Cone photoreceptors provide the foundation of most of human visual experience, but because they are smaller and less numerous than rods in most mammalian retinas, much less is known about their physiology. We describe new techniques and approaches which are helping to provide a better understanding of cone function. We focus on several outstanding issues, including the identification of the features of the phototransduction cascade that are responsible for the more rapid kinetics and decreased sensitivity of the cone response, the roles of inner-segment voltage-gated and Ca2+-activated channels, the means by which cones remain responsive even in the brightest illumination, mechanisms of cone visual pigment regeneration in constant light, and energy consumption of cones in comparison to that of rods.
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34
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Murenu E, Kostidis S, Lahiri S, Geserich AS, Imhof A, Giera M, Michalakis S. Metabolic Analysis of Vitreous/Lens and Retina in Wild Type and Retinal Degeneration Mice. Int J Mol Sci 2021; 22:ijms22052345. [PMID: 33652907 PMCID: PMC7956175 DOI: 10.3390/ijms22052345] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 02/19/2021] [Accepted: 02/23/2021] [Indexed: 02/06/2023] Open
Abstract
Photoreceptors are the light-sensing cells of the retina and the major cell type affected in most inherited retinal degenerations. Different metabolic pathways sustain their high energetic demand in physiological conditions, particularly aerobic glycolysis. The principal metabolome of the mature retina has been studied, but only limited information is available on metabolic adaptations in response to key developmental events, such as eye opening. Moreover, dynamic metabolic changes due to retinal degeneration are not well understood. Here, we aimed to explore and map the ocular metabolic dynamics induced by eye opening in healthy (wild type) or Pde6b-mutant (retinal degeneration 1, Rd1) mice, in which photoreceptors degenerate shortly after eye opening. To unravel metabolic differences emerging before and after eye opening under physiological and pathophysiological conditions, we performed nuclear magnetic resonance (NMR) spectroscopy-based metabolome analysis of wild type and Rd1 retina and vitreous/lens. We show that eye opening is accompanied by changes in the concentration of selected metabolites in the retina and by alterations in the vitreous/lens composition only in the retinal degeneration context. As such, we identify NAcetylaspartate as a potential novel vitreous/lens marker reflecting progressive retinal degeneration. Thus, our data can help elucidating mechanisms underlying key events in retinal physiology and reveal changes occurring in pathology, while highlighting the importance of the vitreous/lens in the characterization of retinal diseases.
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Affiliation(s)
- Elisa Murenu
- Department of Ophthalmology, Ludwig-Maximilians-Universität München, Mathildenstraße 8, 80336 Munich, Germany;
- Department of Pharmacy, Ludwig-Maximilians Universität München, Butenandtstr. 7, 81377 Munich, Germany;
| | - Sarantos Kostidis
- Leiden University Medical Center, Center for Proteomics & Metabolomics, P.O. Box 9600, 2300 RC Leiden, The Netherlands; (S.K.); (M.G.)
| | - Shibojyoti Lahiri
- Biomedical Center Munich-Molecular Biology, Ludwig-Maximilians-Universität München, Großhaderner Strasse 9, 82152 Planegg-Martinsried, Germany; (S.L.); (A.I.)
| | - Anna S. Geserich
- Department of Pharmacy, Ludwig-Maximilians Universität München, Butenandtstr. 7, 81377 Munich, Germany;
| | - Axel Imhof
- Biomedical Center Munich-Molecular Biology, Ludwig-Maximilians-Universität München, Großhaderner Strasse 9, 82152 Planegg-Martinsried, Germany; (S.L.); (A.I.)
| | - Martin Giera
- Leiden University Medical Center, Center for Proteomics & Metabolomics, P.O. Box 9600, 2300 RC Leiden, The Netherlands; (S.K.); (M.G.)
| | - Stylianos Michalakis
- Department of Ophthalmology, Ludwig-Maximilians-Universität München, Mathildenstraße 8, 80336 Munich, Germany;
- Department of Pharmacy, Ludwig-Maximilians Universität München, Butenandtstr. 7, 81377 Munich, Germany;
- Correspondence: ; Tel.: +49-89-2180-77325
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35
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Pan WW, Wubben TJ, Besirli CG. Photoreceptor metabolic reprogramming: current understanding and therapeutic implications. Commun Biol 2021; 4:245. [PMID: 33627778 PMCID: PMC7904922 DOI: 10.1038/s42003-021-01765-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 01/28/2021] [Indexed: 02/06/2023] Open
Abstract
Acquired and inherited retinal disorders are responsible for vision loss in an increasing proportion of individuals worldwide. Photoreceptor (PR) death is central to the vision loss individuals experience in these various retinal diseases. Unfortunately, there is a lack of treatment options to prevent PR loss, so an urgent unmet need exists for therapies that improve PR survival and ultimately, vision. The retina is one of the most energy demanding tissues in the body, and this is driven in large part by the metabolic needs of PRs. Recent studies suggest that disruption of nutrient availability and regulation of cell metabolism may be a unifying mechanism in PR death. Understanding retinal cell metabolism and how it is altered in disease has been identified as a priority area of research. The focus of this review is on the recent advances in the understanding of PR metabolism and how it is critical to reduction-oxidation (redox) balance, the outer retinal metabolic ecosystem, and retinal disease. The importance of these metabolic processes is just beginning to be realized and unraveling the metabolic and redox pathways integral to PR health may identify novel targets for neuroprotective strategies that prevent blindness in the heterogenous group of retinal disorders.
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Affiliation(s)
- Warren W Pan
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, Ann Arbor, MI, USA
| | - Thomas J Wubben
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, Ann Arbor, MI, USA.
| | - Cagri G Besirli
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, Ann Arbor, MI, USA.
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36
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Tezel T, Ruff A. Retinal cell transplantation in retinitis pigmentosa. Taiwan J Ophthalmol 2021; 11:336-347. [PMID: 35070661 PMCID: PMC8757529 DOI: 10.4103/tjo.tjo_48_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 10/10/2021] [Indexed: 11/25/2022] Open
Abstract
Retinitis pigmentosa is the most common hereditary retinal disease. Dietary supplements, neuroprotective agents, cytokines, and lately, prosthetic devices, gene therapy, and optogenetics have been employed to slow down the retinal degeneration or improve light perception. Completing retinal circuitry by transplanting photoreceptors has always been an appealing idea in retinitis pigmentosa. Recent developments in stem cell technology, retinal imaging techniques, tissue engineering, and transplantation techniques have brought us closer to accomplish this goal. The eye is an ideal organ for cell transplantation due to a low number of cells required to restore vision, availability of safe surgical and imaging techniques to transplant and track the cells in vivo, and partial immune privilege provided by the subretinal space. Human embryonic stem cells, induced pluripotential stem cells, and especially retinal organoids provide an adequate number of cells at a desired developmental stage which may maximize integration of the graft to host retina. However, stem cells must be manufactured under strict good manufacturing practice protocols due to known tumorigenicity as well as possible genetic and epigenetic stabilities that may pose a danger to the recipient. Immune compatibility of stem cells still stands as a problem for their widespread use for retinitis pigmentosa. Transplantation of stem cells from different sources revealed that some of the transplanted cells may not integrate the host retina but slow down the retinal degeneration through paracrine mechanisms. Discovery of a similar paracrine mechanism has recently opened a new therapeutic path for reversing the cone dormancy and restoring the sight in retinitis pigmentosa.
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37
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Mitochondria: The Retina's Achilles' Heel in AMD. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1256:237-264. [PMID: 33848005 DOI: 10.1007/978-3-030-66014-7_10] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Strong experimental evidence from studies in human donor retinas and animal models supports the idea that the retinal pathology associated with age-related macular degeneration (AMD) involves mitochondrial dysfunction and consequent altered retinal metabolism. This chapter provides a brief overview of mitochondrial structure and function, summarizes evidence for mitochondrial defects in AMD, and highlights the potential ramifications of these defects on retinal health and function. Discussion of mitochondrial haplogroups and their association with AMD brings to light how mitochondrial genetics can influence disease outcome. As one of the most metabolically active tissues in the human body, there is strong evidence that disruption in key metabolic pathways contributes to AMD pathology. The section on retinal metabolism reviews cell-specific metabolic differences and how the metabolic interdependence of each retinal cell type creates a unique ecosystem that is disrupted in the diseased retina. The final discussion includes strategies for therapeutic interventions that target key mitochondrial pathways as a treatment for AMD.
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38
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Peng X, Gao L, Liu Y. Cell-based therapies for age-related macular degeneration: cell replacement versus paracrine effects. Neural Regen Res 2021; 16:1214-1215. [PMID: 33269782 PMCID: PMC8224131 DOI: 10.4103/1673-5374.300443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Affiliation(s)
- Xiaoyan Peng
- Department of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Ling Gao
- Department of Ophthalmology, Second Affiliated Hospital of Xiangya Medical School, Central South China University, Changsha, Hunan Province, China
| | - Yongqing Liu
- James Graham Brown Cancer Center; Department of Ophthalmology and Visual Sciences; Birth Defects Center, University of Louisville School of Medicine, Louisville, KY, USA
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39
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Lee SJ, Wang W, Jin L, Lu X, Gao L, Chen Y, Liu T, Emery D, Vukmanic E, Liu Y, Kaplan HJ, Dean DC. Rod photoreceptor clearance due to misfolded rhodopsin is linked to a DAMP-immune checkpoint switch. J Biol Chem 2021; 296:100102. [PMID: 33214223 PMCID: PMC7949052 DOI: 10.1074/jbc.ra120.016053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 11/13/2020] [Accepted: 11/19/2020] [Indexed: 01/19/2023] Open
Abstract
Chronic endoplasmic reticulum stress resulting from misfolding of the visual pigment rhodopsin (RHO) can lead to loss of rod photoreceptors, which initiates retinitis pigmentosa, characterized initially by diminished nighttime and peripheral vision. Cone photoreceptors depend on rods for glucose transport, which the neurons use for assembly of visual pigment-rich structures; as such, loss of rods also leads to a secondary loss of cone function, diminishing high-resolution color vision utilized for tasks including reading, driving, and facial recognition. If dysfunctional rods could be maintained to continue to serve this secondary cone preservation function, it might benefit patients with retinitis pigmentosa, but the mechanisms by which rods are removed are not fully established. Using pigs expressing mutant RHO, we find that induction of a danger-associated molecular pattern (DAMP) "eat me" signal on the surface of mutant rods is correlated with targeting the live cells for (PrCR) by retinal myeloid cells. Glucocorticoid therapy leads to replacement of this DAMP with a "don't eat me" immune checkpoint on the rod surface and inhibition of PrCR. Surviving rods then continue to promote glucose transport to cones, maintaining their viability.
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Affiliation(s)
- Sang Joon Lee
- Department of Ophthalmology and Visual Sciences, University of Louisville Health Sciences Center, Louisville, Kentucky, USA; Department of Ophthalmology, Kosin University College of Medicine, Seo-gu, Busan, Korea
| | - Wei Wang
- Department of Ophthalmology and Visual Sciences, University of Louisville Health Sciences Center, Louisville, Kentucky, USA
| | - Lei Jin
- Department of Ophthalmology and Visual Sciences, University of Louisville Health Sciences Center, Louisville, Kentucky, USA; Department of Ophthalmology, The Third People's Hospital of Dalian, Dalian Medical University, Dalian, China
| | - Xiaoqin Lu
- Department of Ophthalmology and Visual Sciences, University of Louisville Health Sciences Center, Louisville, Kentucky, USA; Department of Medicine, University of Louisville Health Sciences Center, Louisville, Kentucky, USA
| | - Lei Gao
- Department of Ophthalmology and Visual Sciences, University of Louisville Health Sciences Center, Louisville, Kentucky, USA; Department of Hematology, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Yao Chen
- Department of Ophthalmology and Visual Sciences, University of Louisville Health Sciences Center, Louisville, Kentucky, USA; Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, China
| | - Tingting Liu
- Department of Ophthalmology and Visual Sciences, University of Louisville Health Sciences Center, Louisville, Kentucky, USA; Department of Ophthalmology, The Third People's Hospital of Dalian, Dalian Medical University, Dalian, China
| | - Douglas Emery
- Department of Ophthalmology and Visual Sciences, University of Louisville Health Sciences Center, Louisville, Kentucky, USA; Department of Medicine, University of Louisville Health Sciences Center, Louisville, Kentucky, USA
| | - Eric Vukmanic
- Department of Ophthalmology and Visual Sciences, University of Louisville Health Sciences Center, Louisville, Kentucky, USA; Department of Medicine, University of Louisville Health Sciences Center, Louisville, Kentucky, USA
| | - Yongqing Liu
- Department of Ophthalmology and Visual Sciences, University of Louisville Health Sciences Center, Louisville, Kentucky, USA; Department of Medicine, University of Louisville Health Sciences Center, Louisville, Kentucky, USA
| | - Henry J Kaplan
- Department of Ophthalmology and Visual Sciences, University of Louisville Health Sciences Center, Louisville, Kentucky, USA
| | - Douglas C Dean
- Department of Ophthalmology and Visual Sciences, University of Louisville Health Sciences Center, Louisville, Kentucky, USA; Department of Medicine, University of Louisville Health Sciences Center, Louisville, Kentucky, USA.
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Piri N, Grodsky J, Kaplan H. Gene therapy for retinitis pigmentosa. Taiwan J Ophthalmol 2021; 11:348-351. [PMID: 35070662 PMCID: PMC8757518 DOI: 10.4103/tjo.tjo_47_21] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 10/02/2021] [Indexed: 11/23/2022] Open
Abstract
Rhodopsin-mediated autosomal dominant retinitis pigmentosa (RP) is the most common cause of RP in North America. There is no proven cure for the disease, and multiple approaches are being studied. Gene therapy is an evolving field in medicine and ophthalmology. In this review, we will go over the basic concept of gene therapy and the different types of gene therapy that are currently being studied to treat this disease.
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Ozmert E, Demirel S, Arslan U, Biçer Ö, Ahlat O, Şermet F. Effect of autologous growth factors on apoptosis and thickness of the outer nuclear layer in an experimental retinal degeneration model. Growth Factors 2020; 38:247-258. [PMID: 34236295 DOI: 10.1080/08977194.2021.1948842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Retinal pigment epithelium and photoreceptor cells are a microenvironment where 90 different peptides are synthesized for transduction, visual cycle, intracellular electron transport chain, and removal of metabolic wastes. Depending on the inheritance pattern, either mutant proteins accumulate inside the cells or the energy cycle is disrupted. Disruption of homeostasis causes the cells to switch to the dormant phase; if the improper conditions last longer, then apoptosis eventually develops resulting in a loss of visual function. In neural tissues, growth factors such as neural growth factor, brain-derived neurotrophic factor, ciliary neurotrophic factor, and insulin-like growth factor are regulatory peptides for intracellular energy cycle and intracellular digestion. In this study, it has been shown histopathologically that autologous growth factors can prevent apoptosis and prevent loss of outer retinal thickness in the retinal degeneration model created with sodium iodate.
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Affiliation(s)
- Emin Ozmert
- Faculty of Medicine, Department of Ophthalmology, Ankara University, Ankara, Turkey
| | - Sibel Demirel
- Faculty of Medicine, Department of Ophthalmology, Ankara University, Ankara, Turkey
| | - Umut Arslan
- Technopolis, Ankara University, Ankara, Turkey
| | - Özlem Biçer
- Faculty of Medicine, Department of Ophthalmology, Ankara University, Ankara, Turkey
| | - Ozan Ahlat
- Faculty of Veterinary Medicine, Department of Pathology, Ankara University, Ankara, Turkey
| | - Figen Şermet
- Faculty of Medicine, Department of Ophthalmology, Ankara University, Ankara, Turkey
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Autologous Retinal Transplantation for Primary and Refractory Macular Holes and Macular Hole Retinal Detachments: The Global Consortium. Ophthalmology 2020; 128:672-685. [PMID: 33045315 DOI: 10.1016/j.ophtha.2020.10.007] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 09/30/2020] [Accepted: 10/05/2020] [Indexed: 11/22/2022] Open
Abstract
PURPOSE To report the anatomic and functional outcomes of autologous retinal transplantation (ART). DESIGN Multicenter, retrospective, interventional, consecutive case series. PARTICIPANTS One hundred thirty eyes of 130 patients undergoing ART for the repair of primary and refractory macular holes (MHs), as well as combined MH-rhegmatogenous retinal detachment (MH-RRD), between January 2017 and December 2019. METHODS All patients underwent pars plana vitrectomy and ART, with surgeon modification of intraoperative variables. A large array of preoperative, intraoperative, and postoperative data was collected. Two masked reviewers graded OCT images. Multivariate statistical analysis and subgroup analysis were performed. MAIN OUTCOME MEASURES Macular hole closure rate, visual acuity (VA), external limiting membrane and ellipsoid zone (EZ) band integrity, and alignment of neurosensory layers (ANL) on OCT. RESULTS One hundred thirty ART surgeries were performed by 33 vitreoretinal surgeons worldwide. Patient demographics were: mean age of 63 ± 6.3 years, 58% female, 41% White, 23% Black, 19% Asian, and 17% Latino. Preoperative VA was 1.37 ± 0.12 logarithm of the minimum angle of resolution (logMAR; Snellen equivalent, approximately 20/500), which improved significantly to 1.05 ± 0.09 logMAR (Snellen equivalent, approximately 20/225; P < 0.001) after surgery (mean follow-up, 8.6 ± 0.8 months). Autologous retinal transplantation was performed for primary MH repair in 27% of patients (n = 35), for refractory MH in 58% of patients (n = 76; mean number of previous surgeries, 1.6 ± 0.2), and for MH-RRD in 15% of patients (n = 19). Mean maximum MH diameter was 1470 ± 160 μm, mean minimum diameter was 840 ± 94 μm, and mean axial length was 24.6 ± 3.2 mm. Overall, 89% of MHs closed (78.5% complete; 10% small eccentric defect), with a 95% closure rate in MH-RRD (68.4% complete; 26.3% small eccentric defect). Visual acuity improved by at least 3 lines in 43% of eyes and by at least 5 lines in 29% of eyes. Reconstitution of the EZ (P = 0.02) and ANL (P = 0.01) on OCT were associated with better final VA. Five cases of ART graft dislocation (3.8%), 5 cases of postoperative retinal detachment (3.8%), and 1 case of endophthalmitis (0.77%) occurred. CONCLUSIONS In this global experience, patients undergoing ART for large primary and refractory MHs and MH-RRDs achieved good anatomic and functional outcomes, with low complication rates despite complex surgical pathologic features.
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Metabolic Deregulation of the Blood-Outer Retinal Barrier in Retinitis Pigmentosa. Cell Rep 2020; 28:1323-1334.e4. [PMID: 31365873 PMCID: PMC6693665 DOI: 10.1016/j.celrep.2019.06.093] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 05/31/2019] [Accepted: 06/26/2019] [Indexed: 02/07/2023] Open
Abstract
Retinitis pigmentosa (RP) initiates with diminished rod photoreceptor function, causing peripheral and nighttime vision loss. However, subsequent loss of cone function and high-resolution daylight and color vision is most debilitating. Visual pigment-rich photoreceptor outer segments (OS) undergo phagocytosis by the retinal pigment epithelium (RPE), and the RPE also acts as a blood-outer retinal barrier transporting nutrients, including glucose, to photoreceptors. We provide evidence that contact between externalized phosphatidylserine (PS) on OS tips and apical RPE receptors activates Akt, linking phagocytosis with glucose transport to photoreceptors for new OS synthesis. As abundant mutant rod OS tips shorten in RP, Akt activation is lost, and onset of glucose metabolism in the RPE and diminished glucose transport combine to cause photoreceptor starvation and accompanying retinal metabolome changes. Subretinal injection of OS tip mimetics displaying PS restores Akt activation, glucose transport, and cone function in end-stage RP after rods are lost. Wang et al. show that onset of glucose metabolism in the retinal pigment epithelium (RPE), which acts as the blood-outer retinal barrier, and inhibition of RPE glucose transport to photoreceptors combine to cause photoreceptor starvation and vision loss in retinitis pigmentosa.
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Özmert E, Arslan U. Management of retinitis pigmentosa by Wharton's jelly-derived mesenchymal stem cells: prospective analysis of 1-year results. Stem Cell Res Ther 2020; 11:353. [PMID: 32787913 PMCID: PMC7425139 DOI: 10.1186/s13287-020-01870-w] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 07/29/2020] [Accepted: 07/31/2020] [Indexed: 12/31/2022] Open
Abstract
PURPOSE The aim of the study was to investigate annual structural and functional results, and their correlation with inheritance pattern of retinitis pigmentosa (RP) patients who were treated with Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs). MATERIAL AND METHODS This prospective, sequential, open-label phase-3 clinical study was conducted at Ankara University Faculty of Medicine, Department of Ophthalmology, between April 2019 and May 2020. The study included 34 eyes from 32 retinitis pigmentosa patients of various genotypes who were enrolled in the stem cells clinical trial. The patients were followed for 12 months after the WJ-MSCs transplantation into subtenon space and evaluated with consecutive examinations. Genetic mutations were investigated using a retinitis pigmentosa panel sequencing method consisting of 90 genes. All patients underwent a complete routine ophthalmic examination with best corrected visual acuity, optical coherence tomography angiography, visual field, and full-field electroretinography. Quantitative data obtained from baseline (T0), 6th month (T1), and 12th month (T2) examinations were compared. RESULTS According to timepoints at T0, T1, and T2: The mean outer retinal thickness was 100.3 μm, 119.1 μm, and 118.0 μm, respectively (p = 0.01; T0 < T1, T2). The mean horizontal ellipsoid zone width were 2.65 mm, 2.70 mm, and 2.69 mm respectively (p = 0.01; T0 < T1, T2). The mean best corrected visual acuity (BCVA) were 70.5 letters, 80.6 letters, and 79.9 letters, respectively (p = 0.01; T0 < T1, T2). The mean fundus perimetry deviation index (FPDI) was 8.0%, 11.4%, and 11.6%, respectively (p = 0.01; T0 < T1, T2). The mean full-field flicker ERG parameters at T0, T1, and T2: amplitudes were 2.4 mV, 5.0 mV, and 4.6 mV, respectively (p = 0.01; T0 < T1, T2). Implicit time were 43.3 ms, 37.9 ms, and 38.6 ms, respectively (p = 0.01; T0 > T1, T2). According to inheritance pattern, BCVA, FPDI, ERG amplitude, and implicit time data improved significantly in autosomal dominant (AD) and in autosomal recessive (AR) RP at 1 year follow-up (pAD = 0.01, pAR = 0.01; pAD = pAR > pX-linked). No ocular or systemic adverse events related to the surgical methods and/or WJ-MSCs were observed during the 1 year follow-up period. CONCLUSION Subtenon transplantation of WJ-MSCs was found to be effective and safe in the treatment of RP during the first year, similar to the sixth month's results. In autosomal dominant and autosomal recessive inheritance of RP, regardless of the genetic mutations, subtenon administration of WJ-MSCs can be considered an effective and safe option without any adverse effect for slowing or stopping the disease progression. TRIAL REGISTRATION ClinicalTrials.gov, NCT04224207 . Registered 8 January 2020.
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Affiliation(s)
- Emin Özmert
- Faculty of Medicine Department of Ophthalmology, Ankara University, Ankara, Turkey
| | - Umut Arslan
- Bioretina Eye Clinic, Ankara University Technopolis, Neorama Ofis 55-56 Yaşam Cad. No 13/A Beştepe, Yenimahalle, Ankara, Turkey
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Abstract
We have used recent measurements of mammalian cone light responses and voltage-gated currents to calculate cone ATP utilization and compare it to that of rods. The largest expenditure of ATP results from ion transport, particularly from removal of Na+ entering outer segment light-dependent channels and inner segment hyperpolarization-activated cyclic nucleotide-gated channels, and from ATP-dependent pumping of Ca2+ entering voltage-gated channels at the synaptic terminal. Single cones expend nearly twice as much energy as single rods in darkness, largely because they make more synapses with second-order retinal cells and thus must extrude more Ca2+ In daylight, cone ATP utilization per cell remains high because cones never remain saturated and must continue to export Na+ and synaptic Ca2+ even in bright illumination. In mouse and human retina, rods greatly outnumber cones and consume more energy overall even in background light. In primates, however, the high density of cones in the fovea produces a pronounced peak of ATP utilization, which becomes particularly prominent in daylight and may make this part of the retina especially sensitive to changes in energy availability.
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Weh E, Lutrzykowska Z, Smith A, Hager H, Pawar M, Wubben TJ, Besirli CG. Hexokinase 2 is dispensable for photoreceptor development but is required for survival during aging and outer retinal stress. Cell Death Dis 2020; 11:422. [PMID: 32499533 PMCID: PMC7272456 DOI: 10.1038/s41419-020-2638-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 05/15/2020] [Accepted: 05/18/2020] [Indexed: 02/06/2023]
Abstract
Photoreceptor death is the ultimate cause of vision loss in many retinal degenerative conditions. Identifying novel therapeutic avenues for prolonging photoreceptor health and function has the potential to improve vision and quality of life for patients suffering from degenerative retinal disorders. Photoreceptors are metabolically unique among other neurons in that they process the majority of their glucose via aerobic glycolysis. One of the main regulators of aerobic glycolysis is hexokinase 2 (HK2). Beyond its enzymatic function of phosphorylating glucose to glucose-6-phosphate, HK2 has additional non-enzymatic roles, including the regulation of apoptotic signaling via AKT signaling. Determining the role of HK2 in photoreceptor homeostasis may identify novel signaling pathways that can be targeted with neuroprotective agents to boost photoreceptor survival during metabolic stress. Here we show that following experimental retinal detachment, p-AKT is upregulated and HK2 translocates to mitochondria. Inhibition of AKT phosphorylation in 661W photoreceptor-like cells results in translocation of mitochondrial HK2 to the cytoplasm, increased caspase activity, and decreased cell viability. Rod-photoreceptors lacking HK2 upregulate HK1 and appear to develop normally. Interestingly, we found that HK2-deficient photoreceptors are more susceptible to acute nutrient deprivation in the experimental retinal detachment model. Additionally, HK2 appears to be important for preserving photoreceptors during aging. We show that retinal glucose metabolism is largely unchanged after HK2 deletion, suggesting that the non-enzymatic role of HK2 is important for maintaining photoreceptor health. These results suggest that HK2 expression is critical for preserving photoreceptors during acute nutrient stress and aging. More specifically, p-AKT mediated translocation of HK2 to the mitochondrial surface may be critical for protecting photoreceptors from acute and chronic stress.
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Affiliation(s)
- Eric Weh
- Department of Ophthalmology and Visual Sciences, University of Michigan, 1000 Wall St., Ann Arbor, MI, 48105, US
| | | | - Andrew Smith
- Department of Ophthalmology and Visual Sciences, University of Michigan, 1000 Wall St., Ann Arbor, MI, 48105, US
| | - Heather Hager
- Department of Ophthalmology and Visual Sciences, University of Michigan, 1000 Wall St., Ann Arbor, MI, 48105, US
| | - Mercy Pawar
- Department of Ophthalmology and Visual Sciences, University of Michigan, 1000 Wall St., Ann Arbor, MI, 48105, US
| | - Thomas J Wubben
- Department of Ophthalmology and Visual Sciences, University of Michigan, 1000 Wall St., Ann Arbor, MI, 48105, US
| | - Cagri G Besirli
- Department of Ophthalmology and Visual Sciences, University of Michigan, 1000 Wall St., Ann Arbor, MI, 48105, US.
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Ropelewski P, Imanishi Y. RPE Cells Engulf Microvesicles Secreted by Degenerating Rod Photoreceptors. eNeuro 2020; 7:ENEURO.0507-19.2020. [PMID: 32376599 PMCID: PMC7242815 DOI: 10.1523/eneuro.0507-19.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 04/10/2020] [Accepted: 04/24/2020] [Indexed: 01/11/2023] Open
Abstract
Rhodopsin is mislocalized to the inner segment plasma membrane (IS PM) in various blinding disorders including autosomal-dominant retinitis pigmentosa caused by class I rhodopsin mutations. In these disorders, rhodopsin-laden microvesicles are secreted into the extracellular milieu by afflicted photoreceptor cells. Using a Xenopus laevis model expressing class I mutant rhodopsin or Na+/K+-ATPase (NKA) fused to Dendra2, we fluorescently labeled the microvesicles and found retinal pigment epithelial (RPE) cells are capable of engulfing microvesicles containing rhodopsin. A unique sorting mechanism allows class I mutant rhodopsin, but not NKA, to be packaged into the microvesicles. Under normal physiological conditions, NKA is not shed as microvesicles to the extracellular space, but is degraded intracellularly. Those studies provide novel insights into protein homeostasis in the photoreceptor IS PM.
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Affiliation(s)
- Philip Ropelewski
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106
| | - Yoshikazu Imanishi
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106
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Arslan U. Management of cystoid macular edema secondary to retinitis pigmentosa via subliminal micropulse yellow laser. Lasers Med Sci 2020; 36:317-323. [PMID: 32363437 DOI: 10.1007/s10103-020-03031-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Accepted: 04/22/2020] [Indexed: 11/30/2022]
Abstract
To investigate the effects of subliminal micropulse yellow laser application on the central macular thickness and best-corrected visual acuity in cystoid macular edema secondary to retinitis pigmentosa patients. This prospective open-label clinical trial, conducted between January 2018 and October 2019, included 32 eyes of 29 patients who had cystoid macular edema secondary to retinitis pigmentosa. Patients were treated by subliminal micropulse yellow laser for one session. Central macular thickness and best-corrected visual acuity changes were investigated just before the treatment and 1 year later after the one session of the treatment. The mean central macular thickness was 651.3 μm before the treatment and 247.7 μm at 12 months after the treatment. The decrease in mean central macular thickness was statistically significant (p = 0.01). Median best-corrected visual acuity was 66.8 ETDRS letters before the treatment and 70.0 letters at 12 months after the treatment. The increase in best-corrected visual acuity was not statistically significant (p = 0.18). Eighty-six percent of the patients stated that the quality of central vision increased and that color vision, contrast sensitivity, and distortion improved. We did not encounter any serious adverse events related to the application of subliminal micropulse yellow laser. The subliminal micropulse yellow laser seems to be a therapeutic, effective, and safe option for the treatment of non-inflammatory and resistant cystoid macular edema secondary to retinitis pigmentosa patients. ClinicalTrials.gov ID: NCT04234438, January 17, 2020.
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Affiliation(s)
- Umut Arslan
- Ankara University Technopolis, Bioretina, Ankara, Turkey. .,Neorama Ofis 55-56 Yaşam Cad, No 13/A Beştepe /Yenimahalle, Ankara, Turkey.
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Management of Retinitis Pigmentosa via Platelet-Rich Plasma or Combination with Electromagnetic Stimulation: Retrospective Analysis of 1-Year Results. Adv Ther 2020; 37:2390-2412. [PMID: 32303913 DOI: 10.1007/s12325-020-01308-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Indexed: 02/07/2023]
Abstract
PURPOSE To investigate whether the natural progression rate of retinitis pigmentosa can be decreased by subtenon autologous platelet-rich plasma application alone or combination with retinal electromagnetic stimulation. METHODS The study includes retrospective analysis of 60 patients with retinitis pigmentosa. Patients constitute three groups with similar demographic characteristics: the combined management group (group 1) consists of 20 patients with retinitis pigmentosa (40 eyes) who received combined retinal electromagnetic stimulation and subtenon platelet-rich plasma; the subtenon platelet-rich plasma-only group (group 2) consisted of 20 patients with retinitis pigmentosa (40 eyes); the natural course (control) group (group 3) consists of 20 patients with retinitis pigmentosa (40 eyes) who did not receive any treatment. Horizontal and vertical ellipsoid zone width, fundus perimetry deviation index, and best corrected visual acuity changes were compared within and between groups after a 1-year follow-up period. RESULTS Detected horizontal ellipsoid zone percentage changes were + 1% in group 1, - 2.85% in group 2, and - 9.36% in group 3 (Δp 1 > 2 > 3). Detected vertical ellipsoid zone percentage changes were + 0.34% in group 1, - 3.05% in group 2, and - 9.09% in group 3 (Δp 1 > 2 > 3). Detected fundus perimetry deviation index percentage changes were + 0.05% in group 1, - 2.68% in group 2, and - 8.78% in group 3 (Δp 1 > 2 > 3). CONCLUSION Platelet-rich plasma is a good source of growth factors, but its half-life is 4-6 months. Subtenon autologous platelet-rich plasma might more effectively slow down photoreceptor loss when repeated as booster injections and combined with retinal electromagnetic stimulation. TRIAL REGISTRATION ClinicalTrials.gov identifier, NCT04252534.
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Rajala RVS. Aerobic Glycolysis in the Retina: Functional Roles of Pyruvate Kinase Isoforms. Front Cell Dev Biol 2020; 8:266. [PMID: 32426353 PMCID: PMC7203425 DOI: 10.3389/fcell.2020.00266] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 03/30/2020] [Indexed: 12/28/2022] Open
Abstract
One hundred years ago, Otto Heinrich Warburg observed that postmitotic retinal cells are the highest oxygen-consuming cells in the body. He compared these cells to actively growing mitotic tumor cells since both cells reprogram glucose for anabolic processes, which include lipid, protein, and RNA/DNA synthesis, and for antioxidant metabolism. To achieve this metabolic reprogramming, cancer cells preferentially express a less active dimeric form, the M2 isoform of pyruvate kinase (PKM2), which shuttles glucose toward the accumulation of glycolytic intermediates that redirect cell activities into anabolic processes. Similar to cancer cells, retinal photoreceptors predominantly express the M2 isoform of PKM2. This isoform performs both metabolic and non-metabolic functions in photoreceptor cells. This review focuses on the metabolic and non-metabolic roles of pyruvate kinases in photoreceptor cell functions.
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Affiliation(s)
- Raju V S Rajala
- Department of Ophthalmology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.,Department of Physiology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.,Department of Cell Biology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.,Dean McGee Eye Institute, Oklahoma City, OK, United States
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