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Yang Liu, Duo Sun, Shireen Khattak, Jingtai Cao, Romano Romano; Retinal structural and functional rescue by subretinal delivery of RS1 gene in mouse models of X-linked juvenile retinoschisis. Invest. Ophthalmol. Vis. Sci. 2021;62(8):1467.
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To evaluate the retinal structural and functional rescue of gene supplementation therapy by subretinal delivery of human RS1 (hRS1) gene carried by AAV2 7m8 vector in mouse models of X-linked juvenile retinoschisis (XLRS).
Male pups from three mouse models, a knockout with inserted lacZ reporter gene, a C59S point mutant substitution, and an R141C point mutant substitution, were used for subretinal injection 1uL of AAV2 7m8-Rho-hRS1 at a titer of 3e13vg/mL on postnatal day 21 in the right eyes, and the left eyes were used as no treatment controls. In vivo retinal structural restoration was evaluated with optical coherence tomography (OCT) and functional rescue with electroretinography (ERG) at 2- and 4-months post injection. Ex vivo retinal tissues harvested at 4 months post injection were flat mounted for immunohistochemistry (IHC) using anti-RS1 and anti-arrestin antibodies to assess hRS1 expression and local retinal photoreceptor protection. A subset of retinal tissues from each group were examined using Western Blot (WB) to confirm hRS1 expression.
Retinal structural rescue was observed 2 months through 4 months post subretinal injection in all three Rs1 mutant mouse models, manifested by disappearance of retinoschisis and well-organized retinal layers on OCT imaging, while controls eyes showed worsening retinal splitting and disorganization over time. Dark adapted ERG b wave at 2 months represented 17.2%, 28.2%, and 23.5% functional restoration, respectively compared to their control eyes, which maintained through 4 months post injection. IHC in retinal flat mounts showed the retinal areas covered by RS1 positive signal were 50-70%. WB under reducing condition showed monomeric hRS1 band from retinal samples of the treated eyes. Cone photoreceptor protection was observed locally where there was, or even no RS1 expression, to varying extent, in the treated eyes evidenced by arrestin immunostaining. The local structural protection and cone cell benefit were also observed in the treated eyes without functional rescue.
Subretinal delivery of AAV RS1 is effective in all three Rs1 mutant mouse models, providing partial retinal structural and functional restoration. Gene supplementation shows promise for XLRS gene therapy. Less invasive delivery method and robust photoreceptor promoters for more efficient treatment are being explored.
This is a 2021 ARVO Annual Meeting abstract.
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