Adjunctive XIAP Anti-apoptotic Therapy in PDEβ Gene-replacement Therapy in the Retinal Degeneration 10 (rd10) Mouse

Abstract

Purpose: : To evaluate the ability of AAV delivery of X-linked inhibitor of apoptosis (XIAP) to enhance the effects-PDEβ gene-replacement therapy in the rd10 mouse, a rodent model of autosomal recessive hereditary retinal degeneration caused by a loss-of-function mutation of the β-subunit of rod cGMP phosphodiesterase gene.

Methods: : The rd10 mice were bred and housed in darkness. Three groups of animals were generated: Group 1 received subretinal AAV-XIAP (AAV5-CBA-XIAP-wPRE) or AAV-GFP (AAV5-UF11) at postnatal age (P) 4 or 21 days; Group 2 received subretinal AAV-XIAP plus AAV- PDEβ (AAV5-smCBA -PDEβ), AAV-GFP plus AAV- PDEβ, or AAV- PDEβ alone at age P4 or P21; Group 3 received subretinal AAV-XIAP at age P4 or 21 days. After injection, the animals were maintained for 4 weeks in the dark before they were moved to a cycling12-hour light / 12-hour dark environment. Animals in Group 3 received a second subretinal injection of AAV- PDEβ (mAAV8-GRK1- PDEβ) 2 weeks after being moved to the light environment. For all groups, histology, immunohistochemistry and ERG were performed at different stages after moving to the light environment.

Results: : Gene replacement therapy with AAV- PDEβ resulted in significant preservation of photoreceptors and ERG responses, but degeneration still occurred after transfer to the light environment. Co-treatment with AAV-XIAP significantly reduced the light-dependent degeneration of the AAV- PDEβ treated retinas. The effect of XIAP was more pronounced in retinas treated at P21 compared to retinas treated at P4. Retinas receiving initial XIAP treatment followed by secondary PDEβ injection showed significant structural preservation and maintained partial ERG responses during the time period of the experiment. AAV-GFP treatment was without effect.

Conclusions: : Adjunctive treatment with the anti-apoptotic gene XIAP confers significant additive effect to gene replacement therapy alone with AAV- PDEβ in the rd10 mouse. In addition AAV-XIAP can prolong the window of opportunity for gene replacement therapy.

Keywords: gene transfer/gene therapy • apoptosis/cell death • neuroprotection