Developing a chemogenetic oxidative damage model to phenocopy dry age-related macular degeneration

Abstract

There is no cure for dry age-related macular degeneration (AMD), and research is challenging due to a lack of good animal models that accurately recapitulate the human disease. Because humans are the only species that develop the full form of AMD, studying its pathogenesis remains particularly challenging. To address this, we developed a chemogenetic oxidative stress model that mimics aspects of dry AMD using Cre-inducible D-amino acid oxidase (DAAO) transgenic mice. In this system, DAAO generates hydrogen peroxide upon exposure to its substrate, D-alanine, allowing spatial and temporal control of oxidative stress. By crossing DAAO mice with cell type specific Cre drivers, we induced oxidative damage selectively in the retinal pigment epithelium (RPE), rod photoreceptors, or vascular endothelial cells. We combined visual function tests (optomotor response and ERG), multimodal imaging (OCT, fundus, and fluorescein angiography), histology (flatmounts, H&E, and immunofluorescence), electron microscopy, and RNA-seq to characterize this model in RPE cells. Oxidative damage targeted to the RPE led to multiple AMD-like phenotypes, including vision loss, RPE and photoreceptor degeneration, hyperreflective foci, epithelial-mesenchymal transition, macrophage infiltration, mitochondrial damage, basal infolding loss, vacuolization, and complement activation. Additionally, we found that this phenotype could be prevented by Nrf2 overexpression by AAV-Best1-Nrf2 subretinal injections in neonates. Additionally, by targeting the oxidative damage to various cell types, RPE, rod photoreceptors and vascular endothelial cells, we examined the autonomous and non-autonomous effects of oxidative stress in the eye. Inducing oxidative damage in the RPE caused degeneration of RPE cells and photoreceptors, and in severe cases, vascular leakage, indicating that oxidative stress in the RPE can elicit both intrinsic and extrinsic degenerative effects. In contrast, we found that targeting oxidative damage to the endothelial cells did not lead to vision loss, or degeneration of RPE or photoreceptors. However, when oxidative damage was directed to rod photoreceptors, low D-alanine concentrations led to RPE degeneration without rod loss, indicating non-autonomous oxidative damage in the eye. Taken together, these findings demonstrate that this chemogenetic model phenocopies dry AMD when targeted to the RPE and provides a powerful system to study cell-autonomous and non-autonomous oxidative damage in the eye.