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Jason M Myers, Mark Christian Butler, Jack M Sullivan; Quantitative Outer Retinal Light Damage in Stargardt-AMD Mouse Model. Invest. Ophthalmol. Vis. Sci. 2016;57(12):779.
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© ARVO (1962-2015); The Authors (2016-present)
Testing a gene therapy approach for Stargardt/dry AMD involves suppression of rod rhodopsin (RHO) expression with hammerhead ribozymes or shRNAs. ABCA4//RDH8 double knockout mice (DKO) have relatively slow retinal degeneration, in our hands, when grown at 10 lux. We test the hypothesis that a retinal light damage model could accelerate photoreceptor damage into a practical kinetic framework to efficiently test gene-based therapeutics.
DKO mice were grown at 10 lux white light. At 2-4 months old they were dark adapted and exposed to 502 nm cyan light generated by high intensity LEDs in a novel Ganzfeld integrating sphere retinal light damage device (Northern Lights) that generates spatially uniform stimuli within the exposure chamber. Pupils were dilated and exposure intensities varied from 400-1700 lux. Duration of exposures were varied from 4 hrs to 24 hrs. Retinal light damage was assessed over a 2 to 12 day period by ultrahigh resolution OCT with measures of outer nuclear layer (ONL) thickness.
DKO model has late emerging photoreceptor degeneration observable by OCT at around 9 months of age in mice grown in 10 lux light on a 12:12 hr light: dark cycle, relative to control C57BL/6J mice which do not manifest retinal degeneration. The Northern Lights instrument delivered at 502 nm a stimulus of 1700 lux, 1200 lux, or 800 lux for 24 hrs. These stimuli cause extensive panretinal degeneration (no measurable ONL) in DKO model but not in C57BL/6J controls. Using 800 lux as a fulcrum stimulus intensity, we explored effects of exposure duration (photon dose) at 800 lux (502 nm) on the retinal degeneration that emerges. Exposures of 12 hrs or 8 hrs cause extensive pan retinal degeneration, but exposure for 4 hrs reveals less extensive measurable ONL degeneration that initially manifests regionally in the DKO retina (ONL Thickness: Control: 59.3 +/- 0.23 um; 800 Lux 4 hr: 49.8 +/- 2 um; Mean +/- SEM) (t-test: -4.68, p= 1.38E-5).
Retinal light damage parameters established for DKO model using 502 nm light that stimulates the rod rhodopsin chromophore (gene therapy target). Under specific conditions (502 nm, 800 lux, 4 hrs) a measurable light induced outer retinal photoreceptor degeneration is manifest. This allows testing of ribozyme or shRNA gene therapeutic agents delivered subretinally in AAV vectors to test for rescue from light-mediated DKO degeneration.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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