Recovery of Retinal Structure and Function After Gene Therapy in a Rs1h–Deficient Mouse Model of Human X–Linked Juvenile Retinoschisis

Abstract

Abstract: : Purpose: X–linked retinoschisis (RS) is one of the most common causes of juvenile macular degeneration in males. Recently, a knock–out mouse deficient in RS1h (RS1h –/–), inactivating the murine ortholog of the human retinoschisis gene, was generated. This line shares key electroretinographic and structural features with the human disease, thus providing a valuable model system in which to develop therapeutic interventions for human RS. We tested the feasibility of AAV vector mediated gene therapy in this model of X–linked retinoschisis. Methods: One microliter (4X10exp10 vector genomes) of a serotype 5 AAV vector containing a 472bp proximal mouse rod opsin promoter driving the human RS1 cDNA (AAV–mOps500–hRS1) was delivered into the subretinal space of the right eyes of 15–day old RS1 –/– mice (n=10). Contralateral left eyes were not injected and served as controls. The efficiency of gene therapy was measured by the full–field electroretinography at 30–, 60–, 90– and 180–days post–injection. Immunohistochemistry and western blot analyses were also conducted on some animals at 90–days post–injection. In addition, scanning laser ophthalmoscopy was performed at 180–days post–injection. Results: All scotopic b–wave amplitudes, reflecting bipolar and possibly Muller cell functions, were significantly improved in injected eyes at 60 and 90 days post injection, but not at 30 days post injection. At 180 days post injection both scotopic and photopic ERG were significantly improved in the treated eye. A similar trend was also apparent for a–wave amplitudes, which were increased in injected eyes compared to contralateral controls over the same experimental period. In addition, delivery of AAV–mOps500–hRS1 into the subretinal space led to the normalization of hRS1 expression and localization, as determined by western blot and immunohistochemistry using RS1 antibody, to improvement of retinal structure, as shown by immunohistochemistry and scanning laser ophthalmoscopy. Conclusions: AAV mediated gene therapy significantly improves retinal function and structure in a RS1h deficient mouse, a model for human X–linked retinoschisis.

Keywords: gene transfer/gene therapy • retinal degenerations: hereditary • photoreceptors