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The article explores advancements in Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and CRISPR-associated protein 9 (Cas9) technology, highlighting its potential for treating genetic diseases of the retina. It discusses the successful application of CRISPR-Cas9 in vivo to target and improve cone photoreceptor function in patients with CEP290-associated inherited retinal degeneration, underscoring its transformative impact on therapeutic approaches for genetic eye diseases.

Age-related macular degeneration (AMD) is one of the leading causes of irreversible blindness in the developed world. Antivascular endothelial growth factor therapy has transformed the management and outcome of neovascular AMD (nAMD), although the need for repeated intravitreal injections--even lifelong--and the related complications, high drug costs, frequent clinic visits and repeated imaging have resulted in an enormous burden both to healthcare systems and patients. The application of gene therapy approaches for sustained delivery of a range of antiangiogenic proteins has the promise of helping to address these aforementioned challenges. A number of early phase clinical trials of gene therapy in nAMD have provided encouraging results, with many more ongoing or anticipated. There remain significant areas of controversy, including regarding the optimal treatment targets, routes of administration and potential safety concerns. In this review we aim to provide an update of the current status of gene therapy for nAMD and briefly discuss future prospects. [ABSTRACT FROM AUTHOR]

Loss of photoreceptors due to retinal degeneration is a major cause of untreatable blindness. Cell replacement therapy, using pluripotent stem cell-derived photoreceptor cells, may be a feasible future treatment. Achieving safe and effective cell replacement is critically dependent on the stringent selection and purification of optimal cells for transplantation. Previously, we demonstrated effective transplantation of post-mitotic photoreceptor precursor cells labelled by fluorescent reporter genes. As genetically labelled cells are not desirable for therapy, here we developed a surface biomarker cell selection strategy for application to complex pluripotent stem cell differentiation cultures. We show that a five cell surface biomarker panel CD73(+)CD24(+)CD133(+)CD47(+)CD15(−) facilitates the isolation of photoreceptor precursors from three-dimensional self-forming retina differentiated from mouse embryonic stem cells. Importantly, stem cell-derived cells isolated using the biomarker panel successfully integrate and mature into new rod photoreceptors in the adult mouse retinae after subretinal transplantation. Conversely, unsorted or negatively selected cells do not give rise to newly integrated rods after transplantation. The biomarker panel also removes detrimental proliferating cells prior to transplantation. Notably, we demonstrate how expression of the biomarker panel is conserved in the human retina and propose that a similar selection strategy will facilitate isolation of human transplantation-competent cells for therapeutic application. S tem C ells 2015;33:2469-2482 [ABSTRACT FROM AUTHOR]

Despite advances in clinical imaging and grading our understanding of retinal immune responses and their morphological correlates in experimental autoimmune uveoretinitis (EAU), has been hindered by the requirement for post-mortem histology. To date, monitoring changes occurring during EAU disease progression and evaluating the effect of therapeutic intervention in real time has not been possible. We wanted to establish whether optical coherence tomography (OCT) could detect intraretinal changes during inflammation and to determine its utility as a tool for accurate scoring of EAU. EAU was induced in C57BL/6J mice and animals evaluated after 15, 26, 36 and 60 days. At each time-point, contemporaneous Spectralis-OCT scanning, topical endoscopic fundal imaging (TEFI), fundus fluorescein angiography (FFA) and CD45-immunolabelled histology were performed. OCT features were further characterised on retinal flat-mounts using immunohistochemistry and 3D reconstruction. Optic disc swelling and vitreous opacities detected by OCT corresponded to CD45+ cell infiltration on histology. Vasculitis identified by FFA and OCT matched perivascular myeloid and T-cell infiltrates and could be differentiated from unaffected vessels. Evolution of these changes could be followed over time in the same eye. Retinal folds were visible and found to encapsulate mixed populations of activated myeloid cells, T-cells and microglia. Using these features, an OCT-based EAU scoring system was developed, with significant correlation to validated histological (Pearson r2 = 0.6392, P<0.0001, n = 31 eyes) and TEFI based scoring systems (r2 = 0.6784, P<0.0001). OCT distinguishes the fundamental features of murine EAU in vivo, permits dynamic assessment of intraretinal changes and can be used to score disease severity. As a result, it allows tissue synchronisation with subsequent cellular and functional assessment and greater efficiency of animal usage. By relating OCT signals with immunohistochemistry in EAU, our findings offer the opportunity to inform the interpretation of OCT changes in human uveitis. [ABSTRACT FROM AUTHOR]

The article focuses on the effort of consultant ophthalmologist James W. B. Bainbridge and colleagues to investigate the use of human genome map in the field of ophthalmology. The investigation focuses on the therapeutic use of genetic code delivered to damaged retinal cells in patients diagnosed with type 2 Leber's congenital amaurosis (LCA). Bainbridge claimed that the restoration of the functionality of molecular chain of events associated with LCA is possible. An explanation of the clinical application of genome map is offered.

The article discusses the future prospect of transplantation for retinal cells in the U.S. It states that age-related macular degeneration (AMD) and Stargardt disease marked an important stage in the development of cell therapies for blinding retinal diseases. It discusses the transplantation of healthy cells to replace diseased cells in the retina demonstrated in clinical trials of retinal translocation surgery, in which retinal pigment epithelium (RPE) from outside the macula is relocated.

A correction to the article "LRG1 promotes angiogenesis by modulating endothelial TGF-β signalling" that was published in the 2013 issue of the periodical is presented.

Phagocytosis requires actin dynamics, but whether actomyosin contractility plays a role in this morphodynamic process is unclear. Here, we show that in the retinal pigment epithelium (RPE), particle binding to Mer Tyrosine Kinase (MerTK), a widely expressed phagocytic receptor, stimulates phosphorylation of the Cdc42 GEF Dbl3, triggering activation of MRCKβ/myosin-II and its coeffector N-WASP, membrane deformation, and cup formation. Continued MRCKβ/myosin-II activity then drives recruitment of a mechanosensing bridge, enabling cytoskeletal force transmission, cup closure, and particle internalization. In vivo, MRCKβ is essential for RPE phagocytosis and retinal integrity. MerTK-independent activation of MRCKβ signaling by a phosphomimetic Dbl3 mutant rescues phagocytosis in retinitis pigmentosa RPE cells lacking functional MerTK. MRCKβ is also required for efficient particle translocation from the cortex into the cell body in Fc receptor-mediated phagocytosis. Thus, conserved MRCKβ signaling at the cortex controls spatiotemporal regulation of actomyosin contractility to guide distinct phases of phagocytosis in the RPE and represents the principle phagocytic effector pathway downstream of MerTK. [ABSTRACT FROM AUTHOR]

Cre Trp1 mice are widely used for conditional retinal pigment epithelium (RPE) gene function studies. Like other Cre/LoxP models, phenotypes in Cre Trp1 mice can be affected by Cre-mediated cellular toxicity, leading to RPE dysfunction, altered morphology and atrophy, activation of innate immunity, and consequent impairment of photoreceptor function. These effects are common among the age-related alterations of RPE that feature in early/intermediate forms of age-related macular degeneration. This article characterizes Cre-mediated pathology in the Cre Trp1 line to elucidate the impact of RPE degeneration on both developmental and pathologic choroidal neovascularization. Nonredundant roles of the two major components of the hypoxia-inducible factor (HIF) family of transcription regulators, HIF1α and HIF2α, were identified. Genetic ablation of Hif1a protected against Cre-induced degeneration of RPE and choroid, whereas ablation of Hif2a exacerbated this degeneration. Furthermore, HIF1α deficiency protected Cre Trp1 mice against laser-induced choroidal neovascularization, whereas HIF2α deficiency exacerbated the phenotype. Cre-mediated degeneration of the RPE in Cre Trp1 mice offers an opportunity to investigate the impact of hypoxia signaling in the context of RPE degeneration. These findings indicate that HIF1α promotes Cre recombinase-mediated RPE degeneration and laser-induced choroidal neovascularization, whereas HIF2α is protective., (Copyright © 2023 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

The generation of retinal organoids from human pluripotent stem cells (hPSC) is now a well-established process that in part recapitulates retinal development. However, hPSC-derived photoreceptors that exhibit well-organized outer segment structures have yet to be observed. To facilitate improved inherited retinal disease modeling, we determined conditions that would support outer segment development in maturing hPSC-derived photoreceptors. We established that the use of antioxidants and BSA-bound fatty acids promotes the formation of membranous outer segment-like structures. Using new protocols for hPSC-derived retinal organoid culture, we demonstrated improved outer segment formation for both rod and cone photoreceptors, including organized stacked discs. Using these enhanced conditions to generate iPSC-derived retinal organoids from patients with X-linked retinitis pigmentosa, we established robust cellular phenotypes that could be ameliorated following adeno-associated viral vector-mediated gene augmentation. These findings should aid both disease modeling and the development of therapeutic approaches for the treatment of photoreceptor disorders., (Copyright © 2022. Published by Elsevier Inc.)

Age-related macular degeneration and other macular diseases result in the loss of light-sensing cone photoreceptors, causing irreversible sight impairment. Photoreceptor replacement may restore vision by transplanting healthy cells, which must form new synaptic connections with the recipient retina. Despite recent advances, convincing evidence of functional connectivity arising from transplanted human cone photoreceptors in advanced retinal degeneration is lacking. Here, we show restoration of visual function after transplantation of purified human pluripotent stem cell-derived cones into a mouse model of advanced degeneration. Transplanted human cones elaborate nascent outer segments and make putative synapses with recipient murine bipolar cells (BCs), which themselves undergo significant remodeling. Electrophysiological and behavioral assessments demonstrate restoration of surprisingly complex light-evoked retinal ganglion cell responses and improved light-evoked behaviors in treated animals. Stringent controls exclude alternative explanations, including material transfer and neuroprotection. These data provide crucial validation for photoreceptor replacement therapy and for the potential to rescue cone-mediated vision., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Major advances in the study of inherited retinal diseases (IRDs) have placed efforts to develop treatments for these blinding conditions at the forefront of the emerging field of precision medicine. As a result, the growth of clinical trials for IRDs has increased rapidly over the past decade and is expected to further accelerate as more therapeutic possibilities emerge and qualified participants are identified. Although guided by established principles, these specialized trials, requiring analysis of novel outcome measures and endpoints in small patient populations, present multiple challenges relative to study design and ethical considerations. This position paper reviews recent accomplishments and existing challenges in clinical trials for IRDs and presents a set of recommendations aimed at rapidly advancing future progress. The goal is to stimulate discussions among researchers, funding agencies, industry, and policy makers that will further the design, conduct, and analysis of clinical trials needed to accelerate the approval of effective treatments for IRDs, while promoting advocacy and ensuring patient safety., Competing Interests: Disclosure: D.A. Thompson, MeiraGTx (F), filed patent on gene therapy (P); A. Iannaccone, Editas Medicine (C), Astellas (C), Roivant Pharma (C), IQVIA (C), Gyroscope/Orbit Biomedical (C), Rhythm Pharmaceuticals (C), Applied Genetic Technologies Corp (F), Allergan (F), Acucela (F), ProQR Therapeutics (F), Foundation Fighting Blindness Clinical Research Institute (F), Alia Therapeutics (S); R.R. Ali, MeiraGTx (S), filed patents on gene and cell therapies (P); V.Y. Arshavsky, None; I. Audo, None; J.W.B. Bainbridge, MeiraGTx (S), filed patents on gene and cell therapies (P); C.G. Besirli, MeiraGTx (F), Spark Therapeutics (F); D.G. Birch, Nightstar Therapeutics/Biogen (C), Applied Genetic Technologies Corp (S), Nacuity Pharmaceuticals (C), Editas Medicine (C), Acucela (S), Foundation Fighting Blindness (C), ProQR Therapeutics (C); K.E. Branham, ProQR Therapeutics (C); A.V. Cideciyan, Patents on gene therapies for RPGR, RHO, and NPHP5-associated IRDs (P); ProQR Therapeutics (F), IVERIC bio (F); S.P. Daiger, Applied Genetic Technologies Corp (S); D. Dalkara, Patent on AAV virions with variant capsid and methods of use (P); J.L. Duncan, 4D Therapeutics (C), Applied Genetic Technologies Corp (C), Editas Medicine (C), Gyroscope (C), Horama (C), Nightstar Therapeutics/Biogen (C), ProQR Therapeutics (C), SparingVision (S), Spark Therapeutics (C), Vedere Bio (C), Acucela (F), Allergan (F), Neurotech (F), Second Sight Medical Products (F); A.T. Fahim, None; J.G. Flannery, None; R. Gattegna, None; J.R. Heckenlively, None; E. Heon, None; K.T. Jayasundera, Editas Medicine (C); N.W. Khan, None; H. Klassen, jCyte (S, I); B.P. Leroy, Bayer (C), Nightstar Therapeutics/Biogen (C), IVERIC bio (C), Novartis Pharma (C), RegenX Bio (C), Vedere Bio (C); Novartis (R), Spark Therapeutics (R); GenSight Biologics (F), ProQR Therapeutics (F); R.S. Molday, Applied Genetic Technologies Corp (S); D.C. Musch, Belite Bio (S), Mactel Group NTMT-03 trial (S), NEI intramural branch clinical trials (S); M.E. Pennesi, Adverum (C), Allergan (C), Astellas (C), Pharmaceuticals (C), Biogen (C), IVERIC bio (C), Novartis (C), Regenix Bio (C), Spark Therapeutics (C), Wave Biosciences (C), Eyevensys (S), Horama (S), Nayan (S), Nacuity Pharmaceuticals (S, I), Ocugen (S, I), Verede (S), ProQR Therapeutics (S), Gensight (S), Applied Genetic Technologies Corp (F), Sanofi (F), Foundation Fighting Blindness (F), ProQR Therapeutics (F), Allergan (F); S.M. Petersen-Jones, None; E.A. Pierce, Astellas (C), Merck (C), Sanofi-Genzyme (C), Wave Therapeutics (C); GenSight Biologics (S), Odylia Therapeutics (S), Opsis Therapeutics (S), Sana Biotechnology (S); CRISPR Therapeutics (F), Spark Therapeutics (F); Editas Medicine (F), MeiraGTx (F), ProQR Therapeutics (F), filed patents on gene and genetic therapies (P); R.C. Rao, None; T.A. Reh, Nayan Pharmaceuticals (C, I); J.A. Sahel, Pixium Vision (S, I), GenSight Biologics (S, I), SparingVision (S, I); Prophesee (I), Chronolife (I); D. Sharon, None; P.A. Sieving, None; E. Strettoi, None; P. Yang, Astellas (C), Applied Genetic Technologies Corp (C); D.N. Zacks, ONL Therapeutics (C, I, P), (Copyright 2020 The Authors.)

Purpose: RPE65-associated retinal dystrophy (RPE65-RD) is an early onset, progressive, severe retinal dystrophy. We sought to characterize the natural history of retinal degeneration in affected individuals., Methods: We performed cross-sectional and longitudinal quantitative and qualitative assessments of retinal architecture in RPE65-RD using spectral domain optical coherence tomography (SD-OCT) and fundus autofluorescence (FAF) imaging. Twenty-six subjects (mean age, 14.8 years, range, 5-24 years) with RPE65-RD underwent SD-OCT and FAF imaging, of whom 14 subjects were followed up over time. Foveal thickness (FT), outer nuclear layer thickness (ONLT), ellipsoid zone width (EZW), and ellipsoid zone area (EZA) were calculated where possible. These were correlated with age, best corrected visual acuity (BCVA), and central 30° retinal sensitivity (V30). Intra-observer agreement, test-retest repeatability, and interocular symmetry were also investigated., Results: We identified structural interocular symmetry, the presence of autofluorescence in 46% (12/26) of subjects, and the presence of foveal hypoplasia (associated with significantly worse BCVA) in 50% of subjects. EZW and EZA were measurable in 67% (35/52) and 37% (19/52) of eyes, respectively, with both demonstrating good agreement on repeated measurement. The annual rate of progression using EZW was -300.63 µm/year, and -1.17 mm2/year in EZA. EZW was found to have a statistically significant correlation with BCVA and V30., Conclusions: We identified the presence of autofluorescence in half of our subjects, with foveal hypoplasia also noted in half of our cohort. EZW, and to a lesser extent EZA, were robust measures of retinal degeneration and represent valuable metrics to determine the impact of intervention. (ClinicalTrials.gov number NCT02714816.).

Purpose: RPE65-associated Leber congenital amaurosis (RPE65-LCA) is an early-onset severe retinal dystrophy associated with progressive visual field loss. Phase I/II and III gene therapy trials have identified improved retinal sensitivity but little is known about the natural history of retinal sensitivity in RPE65-LCA., Methods: A total of 19 subjects (aged 9 to 23 years) undertook monocular full-field static perimetry of which 13 subjects were monitored longitudinally. Retinal sensitivity was measured as mean sensitivity (MS) and volumetrically quantified (in decibel-steradian) using visual field modeling and analysis software for the total (VTOT), central 30° (V30) and central 15° (V15) visual field. Correlation was evaluated between retinal sensitivity and age, best-corrected visual acuity (BCVA), contrast sensitivity, vision-related quality of life, and genotype. Test-retest reliability was also investigated., Results: V30 was identified to have a strong, weak, and moderate correlation with age, BCVA and contrast sensitivity respectively. Furthermore, V30 was identified as having a weak linear relationship with the mobility and independence domains of the vision-related quality of life questionnaire. Longitudinal analysis demonstrated a slow loss of retinal sensitivity in this cohort. Subjects with at least one RPE65 nonsense variant appeared to show greater progressive loss of retinal sensitivity in the second decade of life than those without., Conclusions: Volumetric assessment of central 30° visual field sensitivity, V30, is a useful independent measure of retinal function and, in our data, represented the best metric to monitor deterioration of retinal sensitivity in RPE65-LCA. Furthermore, functional correlation with genotype may enable more informed prognostic counseling. (ClinicalTrials.gov number, NCT02714816.)

Loss of photoreceptor cells due to retinal degeneration is one of the main causes of blindness in the developed world. Although there is currently no effective treatment, cell replacement therapy using stem-cell-derived photoreceptor cells may be a feasible future treatment option. In order to ensure safety and efficacy of this approach, robust cell isolation and purification protocols must be developed. To this end, we previously developed a biomarker panel for the isolation of mouse photoreceptor precursors from the developing mouse retina and mouse embryonic stem cell cultures. In the current study we applied this approach to the human pluripotent stem cell (hPSC) system, and identified novel biomarker combinations that can be leveraged for the isolation of human photoreceptors. Human retinal samples and hPSC-derived retinal organoid cultures were screened against 242 human monoclonal antibodies using a high through-put flow cytometry approach. We identified 46 biomarkers with significant expression levels in the human retina and hPSC differentiation cultures. Human retinal cell samples, either from fetal tissue or derived from embryonic and induced pluripotent stem cell cultures, were fluorescence-activated cell sorted (FACS) using selected candidate biomarkers that showed expression in discrete cell populations. Enrichment for photoreceptors and exclusion of mitotically active cells was demonstrated by immunocytochemical analysis with photoreceptor-specific antibodies and Ki-67. We established a biomarker combination, which enables the robust purification of viable human photoreceptors from both human retinae and hPSC-derived organoid cultures. Stem Cells 2018;36:709-722., (© 2018 The Authors Stem Cells published by Wiley Periodicals, Inc. on behalf of AlphaMed Press.)