Early Sub-retinal Delivery of AAV1-Sod2 Protects the Retina in a Mouse Model of Progressive Retinal Degeneration.

Abstract

Purpose : The purpose of our study is to test the sub-retinal delivery of a Sod2 viral vector in a mouse model of geographic atrophy and to determine how long in the disease course this vector will protect the RPE layer from oxidative damage, induced by the genetic deletion of Sod2, once the retinal degeneration is underway.

Methods : We developed a mouse model of retinal oxidative stress (Sod2^flox/flox/VMD2-cre mice) caused by RPE-specific deletion of Sod2, the mitochondrial isoform of MnSOD. These mice show age-dependent retinal degeneration that recapitulates some of the features of dry AMD. We designed Sod2 gene therapy vector by assembling the mouse Sod2 gene with a Myc epitope under the control of a small chicken beta- actin promoter (smCBA) and this vector was packaged into self-complementary AAV serotype 1 vector (AAV1) for RPE specific transduction. We injected subretinally with AAV1-Sod2 or AAV1-GFP vector into the opposite eyes of Sod2^flox/flox/VMD2-cre mice at 6weeks (10 mice), 3 months (9 mice) and 6 months (6 mice) of age. Over a period of 9 months, we monitored retinal degeneration at different time points by electroretinography (ERG) and spectral domain optical coherence tomography (SD-OCT). We used western blotting to determine exogenous myc tagged Sod2 expression by an anti-myc antibody.

Results : One month after sub retinal delivery, AAV1-Sod2 vector resulted in production of myc-tagged MnSOD in the RPE and negligible expression in the neural retina. Fundus imaging showed the widespread expression of GFP by control vector validating the sub-retinal delivery of our vectors. We did not find any adverse functional and structural integrity due to increased expression of Sod2. ERG response and thinning of retinal thickness (SD-OCT) was significantly delayed in Sod2 vector injected eyes to control eye injected with GFP in the eyes of mice treated at 6 weeks compared with those treated at 3 and 6 months of age.

Conclusions : Early delivery of AAV1-Sod2 vector can be used as a tool to reverse oxidative stress in this mouse model of dry AMD. At later times, damage from oxidative stress may not be reversible.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.