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Katharine J Liang, Kenton Woodard, Ellen R Weiss, Jonathan Paul Gaylor, Richard Samulski; Intravitreal AAV-mediated expression of Nrf2 promotes retinal recovery from light-induced retinopathy in mice. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3186.
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© ARVO (1962-2015); The Authors (2016-present)
Oxidative stress is implicated in pathogenesis of age-related macular degeneration (AMD). Nrf2 is a transcription factor that drives antioxidant gene expression. We hypothesized that Nrf2 overexpression can be used as therapy by which antioxidant genes facilitate redox homeostasis. In this study we applied a Nrf2-based gene therapy strategy to rescue a mouse model of light-induced retinal degeneration that recapitulates many features of AMD.
Nrf2 driven by a constitutive CBh promoter was packaged into AAV2.5 and overexpression was verified by western blot. Adult BALB/c mice were intravitreally injected with AAV-Nrf2 (2×109 vector genomes in 1μl) in one eye each. Light damage was administered 6 weeks later for 2 hours (n=5) or 3 hours (n=5) as previously described (Grimm et al., Methods Mol Biol. 2013). Following light damage, retinal thickness and retinal function were monitored at multiple time points using optical coherence tomography (OCT; Micron IV, Phoenix) and electroretinography (ERG; E2, Diagnosys). Results were compared between injected and uninjected eyes as well as to those of age-matched naïve mice (n=5). A two-tailed Student’s t-test was used for statistical analysis.
Two hours of light injury did not cause measureable changes in retinal thickness. However, after 3 hours of light injury, injected eyes had greater retinal thickness compared to uninjected controls, although retinal thickness was decreased in both groups compared to naïve mice (p<0.05). ERG revealed diminished retinal function at acute time points, but by 4 weeks post-light damage AAV-Nrf2 injection facilitated full functional recovery following 2 hours of light damage, and partial recovery following 3 hours of light damage (p<0.05). Protective effects of AAV-Nrf2 were observed out to 3 months post-light damage.
Our results support our hypothesis that Nrf2 overexpression has therapeutic potential in a mouse model of light-induced retinal degeneration. AAV-Nrf2 mediates full rescue of retinal function in mild retinal degeneration, and partial protection in severe degeneration. Based on the timing of AAV-mediated rescue of retinal structure and function, Nrf2 may play a role in proliferation and remodeling following light insult. Future studies will determine whether AAV-Nrf2 mediated rescue is due to modulation of oxidative damage, cell death, and/or proliferation.
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