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DP Petrin, A Baker, S Coupland, P Liston, A Timmers, WW Hauswirth, RG Korneluk, C Tsilfidis; Protection of Photoreceptors from N-methyl-N-nitrosourea Induced Retinal Degeneration by the X-Linked Inhibitor of Apoptosis (XIAP) . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4606.
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Purpose: To investigate the efficacy of an adeno-associated viral vector encoding X-linked inhibitor of apoptosis (XIAP) in preventing photoreceptor apoptosis in a chemical model of retinal degeneration. Methods: Six week old male Sprague-Dawley rats were injected sub-retinally in the right eye with 2mL adeno-associated virus (AAV) encoding either XIAP or GFP (injection control). The left eye served as an uninjected control. Six weeks post injection of AAV-XIAP, the animals received a 60mg/kg dose of N-methyl-N-nitrosourea (MNU), a DNA methylating agent, via intra-peritoneal injection. Electroretinograms were recorded at 0h, 24h, 48h, 72h, and 1-week post-MNU injection. The rats were sacrificed after the ERG recordings and perfused with 4% paraformaldehyde (PFA). The eyes were enucleated and embedded for cryosectioning. Eye sections were analyzed using immunohistochemistry, TUNEL-staining, in-situ hybridization and hematoxylin/eosin (H&E) staining. Taqman analysis was carried out to determine the level of mRNA expression of XIAP in the treated eye. Results: Electroretinograms showed functional protection up to 1-week post MNU injection in the AAV-XIAP injected eye, whereas no response was observed in the control eye. Overexpression of XIAP was found in the treated eye using immunohistochemistry. In-situ hybridization found expression of XIAP in the photoreceptors and Taqman analysis determined at least a 10-fold increase of XIAP mRNA than in the control eye. At 24h post MNU injection, fewer cells had undergone apoptosis in the XIAP-treated eyes in comparison to GFP-injected or untreated eyes. H&E staining revealed that the photoreceptors of the AAV-GFP injected and the uninjected eyes were destroyed by 72h post-MNU injection whereas the AAV-XIAP injected eyes showed structural protection of the photoreceptors at all time points the eyes were sampled up to 1-week post MNU injection. Conclusions: Our results suggest that XIAP is protective against this potent chemotoxic agent and holds promise as a gene therapy payload for retinitis pigmentosa.
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