iPSC-derived Retinal Pigment Epithelium Research Articles

AAV-Mediated Gene Augmentation Therapy Restores Critical Functions in Mutant PRPF31+/− iPSC-Derived RPE Cells

Retinitis pigmentosa (RP) is the most common form of inherited vision loss and is characterized by degeneration of retinal photoreceptor cells and the retinal pigment epithelium (RPE). Mutations in pre-mRNA processing factor 31 (PRPF31) cause dominant RP via haploinsufficiency with incomplete penetrance. There is good evidence that the diverse severity of this disease is a result of differing levels of expression of the wild-type allele among patients. Thus, we hypothesize that PRPF31-related RP will be amenable to treatment by adeno-associated virus (AAV)-mediated gene augmentation therapy. To test this hypothesis, we used induced pluripotent stem cells (iPSCs) with mutations in PRPF31 and differentiated them into RPE cells. The mutant PRPF31 iPSC-RPE cells recapitulate the cellular phenotype associated with the PRPF31 pathology, including defective cell structure, diminished phagocytic function, defects in ciliogenesis, and compromised barrier function. Treatment of the mutant PRPF31 iPSC-RPE cells with AAV-PRPF31 restored normal phagocytosis and cilia formation, and it partially restored structure and barrier function. These results suggest that AAV-based gene therapy targeting RPE cells holds therapeutic promise for patients with PRPF31-related RP.

Induced pluripotent stem cells and derivative photoreceptor precursors as therapeutic cells for retinal degenerations.

The visual impairment associated with inherited retinal degeneration and age-related degeneration of photoreceptors is causing substantial challenges in finding effective therapies. However, induced pluripotent stem cell (iPSC)-derived therapeutic cells such as photoreceptor and retinal pigment epithelium (RPE) cells provide the ultimate options in the rescue of lost photoreceptors to improve the visual function in end-stage degeneration. Retinal cells derived from iPSC are therapeutic cells that could be promising in the field of cell replacement therapy and regenerative medicine. This review presents an overview of the photoreceptor degeneration, methods of iPSC generation, iPSC in retinal disease modeling, summarizes the photoreceptor differentiation protocols, and challenges remained with photoreceptor cell replacement for the treatment of retinal diseases. Thus, the burden and increased incidence of visual impairment emphasizes the need of novel therapy, where iPSC-derived photoreceptor and RPE cells proved to be promising for curing the retinal dysfunction and act as renovation in approach to improve visual function.

Base-Resolution Methylome of Retinal Pigment Epithelial Cells Used in the First Trial of Human Induced Pluripotent Stem Cell-Based Autologous Transplantation.

SummaryThe first-in-human trial of induced pluripotent stem cell (iPSC)-based autologous transplantation was successfully performed on a female patient with age-related macular degeneration. Here we delineated the base-resolution methylome of the iPSC-derived retinal pigment epithelium (iRPE) used in this trial. The methylome of iRPE closely resembled that of native RPE (nRPE), although partially methylated domains (PMDs) emerged in iRPE but not nRPE. Most differentially methylated regions between iRPE and nRPE appeared to originate from (de)methylation errors during differentiation, whereas errors at reprogramming resulted in aberrant genomic imprinting and X chromosome reactivation. Moreover, non-CpG methylation was prominent in nRPE but not iRPE. Intriguingly, xenotransplantation to mouse remodeled the iRPE methylome to demethylate a subset of suppressed genes and accumulate non-CpG methylation, but failed to resolve PMDs and hypermethylated CpG islands. Although the impacts of these alterations remain elusive, our findings should provide a useful guide for methylome analyses of other iPSC-derived cells.

Human iPSC-Derived Retinal Pigment Epithelium: A Model System for Prioritizing and Functionally Characterizing Causal Variants at AMD Risk Loci.

SummaryWe evaluate whether human induced pluripotent stem cell-derived retinal pigment epithelium (iPSC-RPE) cells can be used to prioritize and functionally characterize causal variants at age-related macular degeneration (AMD) risk loci. We generated iPSC-RPE from six subjects and show that they have morphological and molecular characteristics similar to those of native RPE. We generated RNA-seq, ATAC-seq, and H3K27ac ChIP-seq data and observed high similarity in gene expression and enriched transcription factor motif profiles between iPSC-RPE and human fetal RPE. We performed fine mapping of AMD risk loci by integrating molecular data from the iPSC-RPE, adult retina, and adult RPE, which identified rs943080 as the probable causal variant at VEGFA. We show that rs943080 is associated with altered chromatin accessibility of a distal ATAC-seq peak, decreased overall gene expression of VEGFA, and allele-specific expression of a non-coding transcript. Our study thus provides a potential mechanism underlying the association of the VEGFA locus with AMD.

Evaluation of Transplanted Autologous Induced Pluripotent Stem Cell-Derived Retinal Pigment Epithelium in Exudative Age-Related Macular Degeneration

To report the results after 4 years of follow-up in a previously presented first case of induced pluripotent stem cell (iPSC)-derived retinal pigment epithelium (RPE) sheet autologous transplantation using multimodal imaging. Follow-up of a single case. A patient with exudative age-related macular degeneration and polypoidal choroidal vasculopathy. Transplantation of an autologous iPSC-derived RPE cell sheet after removal of choroidal neovascularization (CNV) in September2014. The function of the graft was assessed 4 years after surgery by color fundus photography, spectral-domain (SD) OCT, fluorescein angiography, indocyanine green angiography, and an adaptive optics (AO) retinal camera. At the 4-year follow-up, the transplanted autologous iPSC-derived RPE sheet had survived beneath the retina with slight expansion of the pigmented area and no adverse events. The outer nuclear layer above and adjacent to the graft showed acceptable thickness and an organized structure. Fluorescein angiography and SD OCT suggested the presence of vessel-like structures confined to the grafted area associated with the remaining trunk vessel of preoperative polypoidal choroidal vasculopathy but with no exudative changes. Visual acuity has been stable with no additional injections of anti-vascular endothelial growth factor agent. The choroidal volume at the graft site is relatively preserved when compared with the volume outside this site without RPE after removal of the CNV. Indocyanine green angiography revealed a preserved choriocapillaris around the iPSC-derived RPE sheet. Dark cell-like structures with a predominantly hexagonal arrangement were observed by AO imaging in an area located near the margin of the graft sheet. The average intercell distance was found to be stable over time. Thus far, the grafted iPSC-derived RPE sheet has survived for 4 years and seems to support photoreceptors and choroidal vessels. The morphologic characteristics of the RPE are observed at the transplant site.

Generation of Functional Retinal Pigment Epithelium from Human Induced Pluripotent Stem Cells.

The availability of otherwise not readily accessible intraocular cells via induced pluripotent stem cell (iPSC) technology offers great potential for disease modelling, drug screening, and cell-based transplantation therapy in degenerative ocular disorders. Direct differentiation of iPSCs into retinal pigment epithelium (RPE) is particularly straightforward, and iPSC-derived RPE cell cultures have been demonstrated to yield pure populations of functional cells that display many features of native RPE. Here, I describe a protocol for the generation of iPSC-derived RPE monolayer, their propagation, and cryostorage. A reliable monitoring for functional cell differentiation is achieved by measuring transepithelial resistance.

In vitro Differentiation of Human iPSC-derived Retinal Pigment Epithelium Cells (iPSC-RPE).

Induced Pluripotent Stem Cells (iPSCs) serve as an excellent model system for studying the molecular underpinnings of tissue development. Human iPSC-derived retinal pigment epithelium (iPSC-RPE) cells have fetal-like molecular profiles. Hence, biobanks like iPSCORE, which contain iPSCs generated from hundreds of individuals, are an invaluable resource for examining how common genetic variants exert their effects during RPE development resulting in individuals having different propensities to develop Age-related Macular Degeneration (AMD) as adults. Here, we present an optimized, cost-effective and highly reproducible protocol for derivation of human iPSC-RPE cells using small molecules under serum-free condition and for their quality control using flow cytometry and immunofluorescence. While most previous protocols have required laborious manual selection to enrich for iPSC-RPE cells, our protocol uses whole culture passaging and yields a large number of iPSC-RPE cells with high purity (88-98.1% ZO-1 and MiTF double positive cells). The simplicity and robustness of this protocol would enable its adaption for high-throughput applications involving the generation of iPSC-RPE samples from hundreds of individuals.

Immunological Properties of Human Embryonic Stem Cell-Derived Retinal Pigment Epithelial Cells.

SummaryAge-related macular degeneration is caused by dysfunction and loss of retinal pigment epithelium (RPE) cells, and their transplantation may rescue visual functions and delay disease progression. Human embryonic stem cells (hESCs) may be an unlimited source of RPE cells for allotransplantation. We analyzed the immunomodulatory properties of hESC-derived RPE (hESC-RPE) cells, and showed that they inhibited T cell responses. Co-culture experiments showed that RPE cells inhibited interfon-γ secretion and proliferation of activated T cells. Furthermore, hESC-RPE cells enhanced T cell apoptosis and secretion of the anti-inflammatory cytokine interleukin-10 (IL-10). In addition, RPE cells altered the expression of T cell activation markers, CD69 and CD25. RPE cells transplanted into RCS rats without immunosuppression survived, provided retinal rescue, and enhanced IL-10 blood levels. Our data suggest that hESC-RPE cells have immunosuppressive properties. Further studies will determine if these properties are sufficient to alleviate the need for immunosuppression therapy after their clinical allotransplantation.

Human iPSC-Derived RPE and Retinal Organoids Reveal Impaired Alternative Splicing of Genes Involved in Pre-mRNA Splicing in <i>PRPF31</i> Autosomal Dominant Retinitis Pigmentosa Type 11

Mutations in pre-mRNA processing factors (PRPFs) cause 40% of autosomal dominant retinitis pigmentosa (RP), but it is unclear why mutations in ubiquitously expressed PRPFs cause retinal disease. To understand the molecular basis of this phenotype, we have generated RP type 11 (PRPF31-mutated) patient-specific retinal organoids and retinal pigment epithelium (RPE) from induced pluripotent stem cells (iPSC). Impaired alternative splicing of genes encoding pre-mRNA splicing proteins occurred in patient-specific retinal cells and Prpf31 /- mouse retinae, but not fibroblasts and iPSCs, providing mechanistic insights into retinal-specific phenotypes of PRPFs. RPE was the most affected, characterised by loss of apical-basal polarity, reduced trans-epithelial resistance, phagocytic capacity, microvilli, and cilia length and incidence. Disrupted cilia morphology was observed in patient-derived-photoreceptors that displayed progressive features associated with degeneration and cell stress. In situ gene-editing of a pathogenic mutation rescued key structural and functional phenotypes in RPE and photoreceptors, providing proof-of-concept for future therapeutic strategies.

Pathogenicity of a novel missense variant associated with choroideremia and its impact on gene replacement therapy.

Choroideremia (CHM) is an inherited retinal dystrophy characterised by progressive degeneration of photoreceptors, retinal pigment epithelium (RPE) and underlying choroid. It is caused by loss-of-function mutations in CHM, which has an X-linked inheritance, and is thus an ideal candidate for gene replacement strategies. CHM encodes REP1, which plays a key role in the prenylation of Rab GTPases. We recently showed that an induced pluripotent stem cell (iPSc)-derived RPE model for CHM is fully functional and reproduces the underlying prenylation defect. This criterion can thus be used for testing the pathogenic nature of novel variants. Until recently, missense variants were not associated with CHM. Currently, at least nine such variants have been reported but only two have been shown to be pathogenic. We report here the characterisation of the third pathogenic missense CHM variant, p.Leu457Pro. Clinically, the associated phenotype is indistinguishable from that of loss-of-function mutations. By contrast, this missense variant results in wild type CHM expression levels and detectable levels of mutant protein. The prenylation status of patient-specific fibroblasts and iPSc-derived RPE is within the range observed for loss-of-function mutations, consistent with the clinical phenotype. Lastly, considering the current climate of CHM gene therapy, we assayed whether the presence of mutant REP1 could interfere with a gene replacement strategy by testing the prenylation status of patient-specific iPSc-derived RPE following AAV-mediated gene transfer. Our results show that correction of the functional defect is possible and highlight the predictive value of these models for therapy screening prior to inclusion in clinical trials.

Safe and Effective Cardiac Regenerative Therapy With Human-Induced Pluripotent Stem Cells: How Should We Prepare Pure Cardiac Myocytes?

A clinical study on human-induced pluripotent stem cells (hiPSCs) is underway in the ophthalmic field, and patients with advanced heart failure will be among the next targets for cell transplantation with hiPSCs. Although many approaches for production of hiPSC-derived cardiac myocytes (hiPSC-CMs) have been developed, numerous hurdles must be overcome to achieve safe and effective cardiac regenerative therapy (CRT) . Heart transplantation is the ultimate treatment option for severe heart failure; however, donor organs for transplantation are limited. CRT with hiPSCs has been proposed as an alternative to heart transplantation. In Japan, an iPSC clinical study for age-related macular degeneration has been initiated. This clinical study was feasible because the indication only requires tens of thousands of cells and successful purification of iPSC-derived retinal pigment epithelium by a series of pick up and expand procedures. In contrast, even though >2 years have passed since then, clinical studies for other diseases, including Parkinson disease and spinal cord injury, have not yet been initiated because of the requirement of millions of cells and difficulty in efficient production of pure target cells. Severe heart failure will also be among the next targets. CRT with hiPSCs can be divided into 3 steps: differentiation of large numbers of hiPSC-CMs, elimination of residual human pluripotent stem cells (hPSCs) and purification of hiPSC-CMs, and transplantation of hiPSC-CMs. As several hundred million CMs are required for CRT, it is essential to establish an efficient method for production of pure hiPSC-CMs. 3-Dimensional or 2-dimensional cardiac differentiation systems using recombinant proteins or small molecules related to BMP (bone morphogenic protein) and WNT (Wnt/β catenin) signaling are well-established.1 Despite significant recent improvements in the efficiency of cardiac differentiation, it is not practical to prepare pure CMs without …

A basis for comparison: sensitive authentication of stem cell derived RPE using physiological responses of intact RPE monolayers.

The retinal pigment epithelium (RPE) is a monolayer of highly specialized cells that help maintain the chemical composition of its surrounding subretinal and choroidal extracellular spaces. Retinal cells (photoreceptors in particular), RPE, and choroidal endothelial cells together help ensure a homeostatically stable metabolic environment with exquisitely sensitive functional responses to light. Aging and disease of the RPE impairs its supportive functions contributing to the progressive loss of photoreceptors and vision. The prevalence of RPE associated retinal degenerations has prompted researchers to develop new therapies aimed at replacing the affected RPE with induced pluripotent stem cell (iPSC) or embryonic stem cell (ESC) derived RPE. Despite recent attempts to characterize stem cell derived RPE and to truly authenticate RPE for clinical applications, there remains a significant unmet need to explore the heterogeneity resulting from donor to donor variation as well as the variations inherent in the current processes of cell manufacture. Additionally, it remains unknown whether the starting cell type influences the resulting RPE phenotype following reprogramming and differentiation. To address these questions, we performed a comprehensive evaluation (genomic, structural, and functional) of 15 iPSC derived RPE originating from different donors and tissues and compiled a reference data set for the authentication of iPSC-derived RPE and RPE derived from other stem cell sources.

Evaluation of the Surgical Device and Procedure for Extracellular Matrix-Scaffold-Supported Human iPSC-Derived Retinal Pigment Epithelium Cell Sheet Transplantation.

To develop a clinically applicable transplantation device and surgical procedure for extracellular matrix-scaffold-supported human-induced pluripotent stem cell-derived retinal pigment epithelium (hiPSC-RPE) cell sheet transplantation for clinical use. The developed surgical device consisted of a custom-designed hand piece and a cannula. The subretinal transplantation of hiPSC-RPE cell sheets was performed in 12 rabbits. The results evaluated were the graft condition (damage or fold), side (front or back), position (center, near, far), and direction (anterior, posterior, right, left) immediately after surgery and the graft condition (shrinking or fold) 2 weeks after surgery. These results were evaluated by fundus photography and optical coherence tomography, followed by immersion-fixed histology. All grafts could be transplanted without obvious damage. The transplanted grafts included 2 of 12 folded grafts, 12 of 12 front side, 12 of 12 center position, 10 of 12 anterior direction, and 2 of 12 right direction immediately after surgery, whereas transplantation with a distance between an inlet and an outlet greater than graft and the coaxial direction of the flow paths and the insertion device posed the correct condition and direction. Two weeks after the surgery, the transplanted grafts included two folded grafts and four shrunken grafts; however, complete drainage of subretinal fluid for adhesion between the graft and the host prevented shrunken grafts. A developed surgical device and procedure allow grafts to be transplanted into the targeted transplantation site safely and reproducibly. This surgical method will provide additional information on the advancement of future RPE transplantation therapies.

Repressed SIRT1/PGC-1α pathway and mitochondrial disintegration in iPSC-derived RPE disease model of age-related macular degeneration.

BackgroundStudy of age related macular degeneration (AMD) has been hampered by lack of human models that represent the complexity of the disease. Here we have developed a human in vitro disease model of AMD to investigate the underlying AMD disease mechanisms.MethodsGeneration of iPSCs from retinal pigment epithelium (RPE) of AMD donors, age-matched normal donors, skin fibroblasts of a dry AMD patient, and differentiation of iPSCs into RPE (AMD RPE-iPSC-RPE, normal RPE-iPSC-RPE and AMD Skin-iPSC-RPE, respectively). Immunostaining, cell viability assay and reactive oxygen species (ROS) production under oxidative stress conditions, electron microscopy (EM) imaging, ATP production and glycogen concentration assays, quantitative real time PCR, western blot, karyotyping.ResultsThe AMD RPE-iPSC-RPE and AMD Skin-iPSC-RPE present functional impairment and exhibit distinct disease phenotypes compared to RPE-iPSC-RPE generated from normal donors (Normal RPE-iPSC-RPE). The AMD RPE-iPSC-RPE and AMD Skin-iPSC-RPE show increased susceptibility to oxidative stress and produced higher levels of reactive oxygen species (ROS) under stress in accordance with recent reports. The susceptibility to oxidative stress-induced cell death in AMD RPE-iPSC-RPE and Skin-iPSC-RPE was consistent with inability of the AMD RPE-iPSC-RPE and Skin-iPSC-RPE to increase SOD2 expression under oxidative stress. Phenotypic analysis revealed disintegrated mitochondria, accumulation of autophagosomes and lipid droplets in AMD RPE-iPSC-RPE and AMD Skin-iPSC-RPE. Mitochondrial activity was significantly lower in AMD RPE-iPSC-RPE and AMD Skin-iPSC-RPE compared to normal cells and glycogen concentration was significantly increased in the diseased cells. Furthermore, Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), a regulator of mitochondrial biogenesis and function was repressed, and lower expression levels of NAD-dependent deacetylase sirtuin1 (SIRT1) were found in AMD RPE-iPSC-RPE and AMD Skin-iPSC-RPE as compared to normal RPE-iPSC-RPE.ConclusionsOur studies suggest SIRT1/PGC-1α as underlying pathways contributing to AMD pathophysiology, and open new avenues for development of targeted drugs for treatment of this devastating neurodegenerative disease of the visual system.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-016-1101-8) contains supplementary material, which is available to authorized users.

In Pursuit of Authenticity: Induced Pluripotent Stem Cell-Derived Retinal Pigment Epithelium for Clinical Applications.

The retinal pigment epithelium (RPE) is essential for maintaining visual function. RPE derived from human induced pluripotent stem cells (iPSC-RPE) offer a promising cell-based transplantation therapy for slowing or rescuing RPE-induced visual function loss. For effective treatment, iPSC-RPE must recapitulate the physiology of native human RPE. A set of physiologically relevant functional assays are provided that assess the polarized functional activity and maturation state of the intact RPE monolayer. The present data show that donor-to-donor variability exceeds the tissue-to-tissue variability for a given donor and provides, for the first time, criteria necessary to identify iPSC-RPE most suitable for clinical application.

553. Comparision of AAV Serotypes for Gene Delivery to iPSC Derived RPE

Inherited retinal degenerations, such as retinitis pigmentosa (RP) and Leber congenital amaurosis (LCA), are characterized by progressive impairment of visual function associated with degeneration of retinal pigment epithelium (RPE) and photoreceptors. These monogenic diseases are genetically heterogeneous due to mutations in genes expressed affecting those cells. Gene therapy holds great potential for the treatment of inherited retinal diseases for which there currently is none. Efficient retinal gene transfer has been achieved with several recombinant viral vectors, including those derived from adenovirus, retrovirus, herpesvirus, and adeno-associated virus (AAV). Among these, AAV vectors appear particularly amenable to retinal gene transfer. However the success of any preclinical study depends on the availability of relevant animal models. In situations where suitable animal models are unavailable recent studies have generated proof-of concept data using personalized cell models: induced pluripotent stem cells (iPSC) derived from affected individuals and un-affected controls. With the increasing number of retinal gene therapy paradigms and recombinant vectors, in vitro bioassays characterizing vector transduction efficiency and quality are becoming increasingly important. To date, most in vitro assays using recombinant vector transduction have targeted iPSCs. To elicit additional features relevant to the disease, we differentiated iPSCs to RPE and evaluated the transduction efficiencies of a panel of AAV serotypes. Characterization of iPSC-derived RPE by qRT-PCR, immunohistochemistry, western blot analysis and flow cytometry showed the expression of typical RPE markers, phagocytic ability and gene-expression patterns similar to those of native RPE. Comparison of transduction efficiencies of different AAVs in iPSC-derived RPE was carried out using an enhanced green-fluorescent protein (eGFP) reporter gene driven by the cytomegalovirus immediate-early (CMV) promoter. At 24 to 48 hours post transduction, cells expressing GFP were identified by Typhoon scanner, and flow cytometry. Relative GFP expression was evaluated by using the software, Image-J. Of the tested AAV serotypes, AAV2 transduced iPSC-derived RPE cells most efficiently, followed by AAV7m8, AAV1 and AAV6. Differentiation into retinal neuronal cells types may require use of alternative AAV serotypes in order to obtain transduction efficiencies relevant to determination of therapeutic efficacy.

IPSC-Derived Retinal Pigment Epithelium Allografts Do Not Elicit Detrimental Effects in Rats: A Follow-Up Study.

Phototransduction is accomplished in the retina by photoreceptor neurons and retinal pigment epithelium (RPE) cells. Photoreceptors rely heavily on the RPE, and death or dysfunction of RPE is characteristic of age-related macular degeneration (AMD), a very common neurodegenerative disease for which no cure exists. RPE replacement is a promising therapeutic intervention for AMD, and large numbers of RPE cells can be generated from pluripotent stem cells. However, questions persist regarding iPSC-derived RPE (iPS-RPE) viability, immunogenicity, and tumorigenesis potential. We showed previously that iPS-RPE prevent photoreceptor atrophy in dystrophic rats up until 24 weeks after implantation. In this follow-up study, we longitudinally monitored the same implanted iPS-RPE, in the same animals. We observed no gross abnormalities in the eyes, livers, spleens, brains, and blood in aging rats with iPSC-RPE grafts. iPS-RPE cells that integrated into the subretinal space outlived the photoreceptors and survived for as long as 2 1/2 years while nonintegrating RPE cells were ingested by host macrophages. Both populations could be distinguished using immunohistochemistry and electron microscopy. iPSC-RPE could be isolated from the grafts and maintained in culture; these cells also phagocytosed isolated photoreceptor outer segments. We conclude that iPS-RPE grafts remain viable and do not induce any obvious associated pathological changes.

Modeling the Dynamic AMD-Associated Chronic Oxidative Stress Changes in Human ESC and iPSC-Derived RPE Cells.

Here we use human embryonic stem cells (hESCs) and human-induced pluripotent stem cell (hiPSC)-derived retinal pigment epithelium (RPE) cells to model chronic oxidative stress in vitro. This model allows us to understand the evolution of chronic stress response in RPE in vivo, as well as to monitor microRNAs changes. Finally, we use this in vitro model to identify a partial agonist of NRF2 that is protective against reactive oxygen species (ROS)-induced cytotoxicity. The hESCs and hiPSCs were differentiated toward an RPE fate. Upon maturation, RPE cells were subjected to chronic oxidative stress using Paraquat (PQ). The cells were then analyzed using immunocytochemistry and quantitative RT-PCR to look for changes in gene expression and microRNA changes. Small molecules targeting NRF2 pathways were utilized to look for protection against oxidative stress-induced apoptosis. We show that 160 μM PQ can be used to generate a model of chronic oxidative stress in RPE cells derived from hESCs and hiPSCs. Using this model, we characterize the NRF2 pathway effectors during the early and late stages of chronic oxidative stress and identify microRNAs changes during oxidative stress. We find that hsa-miR144 modulates NRF2 activity during ROS stress. Lastly, we found a small molecule modulator of NRF2 that plays a protective role against oxidative stress-induced RPE apoptosis. In summary, pluripotent stem cell-derived retinal cells can be used to model retinal diseases in a dish. This can provide an unprecedented opportunity to understand the evolution of disease processes and allow us to identify novel therapeutics.

Personalized Medicine: Cell and Gene Therapy Based on Patient-Specific iPSC-Derived Retinal Pigment Epithelium Cells.

Interest in generating human induced pluripotent stem (iPS) cells for stem cell modeling of diseases has overtaken that of patient-specific human embryonic stem cells due to the ethical, technical, and political concerns associated with the latter. In ophthalmology, researchers are currently using iPS cells to explore various applications, including: (1) modeling of retinal diseases using patient-specific iPS cells; (2) autologous transplantation of differentiated retinal cells that undergo gene correction at the iPS cell stage via gene editing tools (e.g., CRISPR/Cas9, TALENs and ZFNs); and (3) autologous transplantation of patient-specific iPS-derived retinal cells treated with gene therapy. In this review, we will discuss the uses of patient-specific iPS cells for differentiating into retinal pigment epithelium (RPE) cells, uncovering disease pathophysiology, and developing new treatments such as gene therapy and cell replacement therapy via autologous transplantation.

Eliminating residual iPS cells for safety in clinical application.

Eliminating residual iPS cells for safety in clinical application.