Differentiated retinal pigmented epithelial (RPE) cells have been obtained from human induced pluripotent stem (hiPS) cells. However, the visual (retinoid) cycle in hiPS-RPE cells has not been adequately examined. Here we determined the expression of functional visual cycle enzymes in hiPS-RPE cells compared with that of isolated wild-type mouse primary RPE (mpRPE) cells in vitro and in vivo. hiPS-RPE cells appeared morphologically similar to mpRPE cells. Notably, expression of certain visual cycle proteins was maintained during cell culture of hiPS-RPE cells, whereas expression of these same molecules rapidly decreased in mpRPE cells. Production of the visual chromophore, 11-cis-retinal, and retinosome formation also were documented in hiPS-RPE cells in vitro. When mpRPE cells with luciferase activity were transplanted into the subretinal space of mice, bioluminance intensity was preserved for >3 months. Additionally, transplantation of mpRPE into blind Lrat^−/− and Rpe65^−/− mice resulted in the recovery of visual function, including increased electrographic signaling and endogenous 11-cis-retinal production. Finally, when hiPS-RPE cells were transplanted into the subretinal space of Lrat^−/− and Rpe65^−/− mice, their vision improved as well. Moreover, histological analyses of these eyes displayed replacement of dysfunctional RPE cells by hiPS-RPE cells. Together, our results show that hiPS-RPE cells can exhibit a functional visual cycle in vitro and in vivo. These cells could provide potential treatment options for certain blinding retinal degenerative diseases.

Purpose. Evaluate the efficacy of potential therapeutics in Rdh8 ^−/− Abca4 ^−/− mice, a rodent model of human age-related macular degeneration (AMD). methods. Therapeutic efficacy of several antioxidant agents (ascorbic acid, α-lipoic acid, α-tocopherol, Mn(III)-tetrakis(4-benzoic acid)-porphyrin, and butylated hydroxytoluene), an immunosuppressive agent with antivascular endothelial growth factor (VEGF) activity (sirolimus, also known as rapamycin), a retinoid cycle inhibitor (retinylamine), and an artificial chromophore (9-cis-retinyl acetate) were evaluated side by side in a recently described murine model of AMD, the Rdh8 ^−/− Abca4 ^−/− mouse. This animal exhibits a retinopathy caused by delayed all-trans-retinal clearance resulting from the absence of both ATP-binding cassette transporter 4 (Abca4) and retinol dehydrogenase 8 (Rdh8) activities. Drug efficacy was evaluated by retinal histologic analyses and electroretinograms (ERGs). results. All tested agents partially prevented atrophic changes in the Rdh8 ^−/− Abca4 ^−/− retina with retinylamine demonstrating the greatest efficacy. A significant reduction of complement deposition on Bruch’s membrane was observed in sirolimus-treated mice, although the severity of retinal degeneration was similar to that observed in antioxidant- and 9-cis-retinyl acetate–treated mice. Sirolimus treatment of 6-month-old Rdh8 ^−/− Abca4 ^−/− mice for 4 months prevented choroidal neovascularization without changing retinal VEGF levels. conclusions. Mechanism-based therapy with retinylamine markedly attenuated degenerative retinopathy in Rdh8 ^−/− Abca4 ^−/− mice. Further understanding of pathogenic mechanisms involved in AMD is needed to develop more effective therapeutics.

Disruption of cellular processes affected by multiple genes and accumulation of numerous insults throughout life dictate the progression of age-related disorders, but their complex etiology is poorly understood. Postmitotic neurons, such as photoreceptor cells in the retina and epithelial cells in the adjacent retinal pigmented epithelium, are especially susceptible to cellular senescence, which contributes to age-related retinal degeneration (ARD). The multigenic and complex etiology of ARD in humans is reflected by the relative paucity of effective compounds for its early prevention and treatment. To understand the genetic differences that drive ARD pathogenesis, we studied A/J mice, which develop ARD more pronounced than that in other inbred mouse models. Although our investigation of consomic strains failed to identify a chromosome associated with the observed retinal deterioration, pathway analysis of RNA-Seq data from young mice prior to retinal pathological changes revealed that increased vulnerability to ARD in A/J mice was due to initially high levels of inflammatory factors and low levels of homeostatic neuroprotective factors. The genetic signatures of an uncompensated preinflammatory state and ARD progression identified here aid in understanding the susceptible genetic loci that underlie pathogenic mechanisms of age-associated disorders, including several human blinding diseases.

J. Neurochem. (2012) 121, 146–156. All‐trans‐retinal and its condensation‐products can cause retinal degeneration in a light‐dependent manner and contribute to the pathogenesis of human macular diseases such as Stargardt’s disease and age‐related macular degeneration. Although these toxic retinoid by‐products originate from rod and cone photoreceptor cells, the contribution of each cell type to light‐induced retinal degeneration is unknown. In this study, the primary objective was to learn whether rods or cones are more susceptible to light‐induced, all‐trans‐retinal‐mediated damage. Previously, we reported that mice lacking enzymes that clear all‐trans‐retinal from the retina, ATP‐binding cassette transporter 4 and retinol dehydrogenase 8, manifested light‐induced retinal dystrophy. We first examined early‐stage age‐related macular degeneration patients and found retinal degenerative changes in rod‐rich rather than cone‐rich regions of the macula. We then evaluated transgenic mice with rod‐only and cone‐like‐only retinas in addition to progenies of such mice inbred with Rdh8^−/−Abca4^−/− mice. Of all these strains, Rdh8^−/−Abca4^−/−mice with a mixed rod–cone population showed the most severe retinal degeneration under regular cyclic light conditions. Intense light exposure induced acute retinal damage in Rdh8^−/−Abca4^−/− and rod‐only mice but not cone‐like‐only mice. These findings suggest that progression of retinal degeneration in Rdh8^−/−Abca4^−/− mice is affected by differential vulnerability of rods and cones to light.

Purpose. Long-term effects of treatment with 9-cis-retinyl acetate (9-cis-R-Ac), an artificial retinoid prodrug, were tested on changes in rod and cone visual functions in mice. methods. The acetyl ester of the functional geometric chromophore 9-cis-retinal was delivered by oral gavage to C57BL/6 female mice. In initial experiments, 10-month-old mice were used for the single treatment with 9-cis-R-Ac or the control vehicle. In long-term experiments, 4-month-old mice were treated with 9-cis-R-Ac monthly for 6 and 10 months. Photoreceptor status was evaluated by various electroretinographic (ERG) techniques, retinoid analyses, and retinal morphology. Opsin, the predicted target of oxidized 9-cis-R-Ac, was purified and its chromophore was characterized. results. Age-related changes observed in vehicle-treated mice at 10 months of age, compared with those in 4-month-old mice, included a progressive decline in ERG responses, such as a decreased rate of dark adaptation and a lowered rhodopsin/opsin ratio. Administration of 9-cis-R-Ac increased the rhodopsin regeneration ratio, and improved ERG responses and dark adaptation. Compared with vehicle-treated control animals, 10- and 14-month-old mice treated monthly with 9-cis-R-Ac for 6 or 10 months exhibited improved dark adaptation. In 14-month-old mice treated monthly, changes in the expression of retina-specific genes in the eye were detected by mRNA expression profiling, but no significant effects in gene expression were detected in the liver and kidney. conclusions. Deteriorating photoreceptor function documented in mice at 10 and 14 versus 4 months of age was improved significantly by long-term, monthly administration of 9-cis-R-Ac. These findings suggest a potential therapeutic approach to prevent age-related retinal dysfunction.