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Haoyu Mao, Marina S. Gorbatyuk, Brian Rossmiller, William W. Hauswirth, Alfred S. Lewin; Long-Term Rescue with Gene Therapy in a Mouse Model of Autosomal Dominant Retinitis Pigmentosa (ADRP). Invest. Ophthalmol. Vis. Sci. 2012;53(14):6448.
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© ARVO (1962-2015); The Authors (2016-present)
Autosomal dominant retinitis pigmentosa (ADRP) is frequently caused by mutations in the RHO gene. The purpose of this study is to demonstrate long term therapeutic effect of a single AAV vector expressing both RHO specific siRNA and mouse rhodopsin cDNA in a transgenic mouse model of ADRP(P23H RHO).
We designed and constructed a combination vector containg the genes for an siRNA resistant rhodopsin (RHO) gene (RHO301) and siRNA301 that targets mouse and human RHO mRNA in order to maintain a normal level of rhodopsin level and to suppress the expression of the P23H human RHO transgene and the endogenous mouse gene. RNA analysis was used to document the knockdown of endogenous RHO RNA and its replacement with resistant RHO301 RNA. Full field scotopic electroretinography and digital fundus imaging were used to monitor the function and surface properties of the retina.
By RT-PCR, eyes treated with AAV-RHO301-siRNA301 had twice the level of rhodopsin transcript compared to untreated retinas. ERG response at series of intensities showed an increase in a- and b-wave amplitudes in AAV- RHO301-siRNA301 injected eyes compared to control injected eyes, over a 9-month time course. This combination treatment was superior to gene transfer of the RHO cDNA alone. At the 9 month time point, the P23H RHO mice treated with AAV- RHO301-siRNA301 had the same ERG amplitudes as non-transgenic mice, while untreated eyes showed more than 5-fold reduction in both a-wave and b-wave. At one month post injection, no significant fundus changes were observed in eyes injected with AAV- RHO301-siRNA301, and this normal fundus was maintained for 9 months. In contrast, P23H retinas without treatment had severe pigmentary abnormalities at 9 months.
The finding that single AAV injection of a combination construct containing gene encoding wild-type rhodopsin and siRNA could preserve the retinal function and structural integrity in this mouse model suggests that the suppression and replacement strategy was beneficial for the long term(>1/3 the lifetime of a mouse). Since this and other knockdown agents we are testing also target human RHO mRNA they may be useful for treatment of ADRP.
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