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Cristhian J Ildefonso, Brianna M Bowman, Manas Ranjan Biswal, Chulbul M Ahmed, Qiuhong Li, Alfred S Lewin; Gene Therapy with the Caspase Activation and Recruitment Domain (CARD) Slows the Retina Degeneration of the Sod2 Knock-Out Mouse Model of Geographic Atrophy. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3387.
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Geographic atrophy is the advanced form of age-related macular degeneration in which the retinal pigmented epithelium (RPE) has been severely damaged by oxidative stress and inflammation. Activation of the NLRP3 inflammasome signaling pathway is involved in the parainflammation associated with AMD. Herein, we tested the efficacy of an inhibitor of caspase-1 in controlling the retinal degeneration observed in both the sodium iodate (NaIO3) model of RPE damage and the Sod2 knock-out model geographic atrophy.
Acute RPE-oxidative injury was induced in 8-week old C57Bl/6J mice one month after intravitreal delivery of an AAV2QUAD-T+V viral vector delivering either GFP or a secreted GFP linked (via a furin cleavage site) to a Tat-fused CARD (sGFP-TatCARD). Mice were evaluated by electroretinography (ERG) at 1 and 4 weeks post NaIO3 injection. Animals were euthanized and flatmounts prepared after the last ERG evaluation. Sod2 knock-out mice were injected intravitreally with AAV2QUAD-T+V delivering either GFP or sGFP-TatCARD. Two cohorts of animals were injected at either 2 or 4 months of age and were followed by ERG and spectral domain optical coherence tomography (SD-OCT).
Eyes treated with sGFP-TatCARD vector showed a recovery of their a-, b- and c-wave amplitudes one month after NaIO3, but recovery of the ERG response was not observed in the GFP treated eyes. Flat mounts from the RPE of these mice showed a partial protection of the RPE layer when compared to eyes treated with the GFP control vector. To test treatment of existing disease, we injected the sGFP-TatCARD vector in the vitreous of Sod2 knock-out mice at 4 months of age. The treated eyes showed a significant reduction in the rate of ERG decline compared to eyes treated with GFP. These eyes also showed a thicker outer segment layer compared to eyes treated with GFP as measured by SD-OCT. To test prevention of disease, we treated Sod2 KO mice at 2 month of age with either sGFP-TatCARD or GFP. We observed a greater protection of the c-wave amplitude in eyes treated with the TatCARD when compared to GFP treated eyes.
Intravitreal delivery of AAV2QUAD-T+V/sGFP-TatCARD can protect the retina from both acute and chronic oxidative damage within the RPE. This protection was observed in the Sod2 knock-out model even after the onset of disease.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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