Theranostics of Photoreceptor-RPE-Choroid Neurovascular Unit in Mouse Models of Eye Diseases

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TITLE: Theranostics of Photoreceptor-RPE-Choroid Neurovascular Unit in Mouse Models of Eye Diseases PI: Robert J. Zawadzki, Ph.D. SUMMARY Inherited and age-related macular degeneration (AMD) are currently responsible for serious vision impairment in over 2 million US residents, with prevalence expected to double by 2040 as the population ages. Degeneration occurs in photoreceptor cells, retinal pigment epithelial (RPE) cells and in the choroidal vasculature, a complex of tightly interdependent tissues in the posterior eye. This project will investigate in vivo the photoreceptor-RPE-choroid complex in animal models of two macular degenerations, RPE mitochondrial dysfunction model and Doyne Honeycomb Retinal Dystrophy. These models recapitulate two major hallmarks of inherited and age related macular degeneration, degeneration of RPE cells, and age- related increase in extracellular deposits between the RPE and Bruch's membrane, which separates the RPE from the choroidal capillary bed. The project will use innovative, cellular-level resolution in vivo imaging combined with additional functional tests to characterize age-related changes in the structure and function of cells of the photoreceptor-RPE-choroid neurovascular unit (PRC-NVU). These studies will be performed longitudinally in cohorts of mice with the genetic defects, and in wild type controls. The studies will test the hypothesis that the primary defects in RPE-Bruch's membrane cause secondary deterioration of photoreceptors and choriocapillaris vasculature. The studies include measures of photoreceptor structure and electrical activity, bleaching and regeneration of the rod visual pigment rhodopsin, mapping of Bruch's membrane thickness, RPE cell autofluorescence, the redox status of RPE cells, and choriocapillaris vascular morphology and flow. At the termination of the study, the choroid-RPE from one eye of each mouse will be imaged with high resolution ex vivo confocal microscopy; the retina from the second eye of each mouse will be evaluated by conventional histological and biochemical measurements performed on light or electron microscopes, to allow validation of in vivo findings. A novel method for delivering drugs to the RPE via near infrared light-degradable nanoparticles will be used to locally target therapeutic agents to ailing RPE cells, and spatially resolved imaging will be used to determine if the therapeutic agents slow and stop disease progression. By combining longitudinal, in vivo imaging and optical nanotherapies, these studies will lay a foundation for locally targeted drug delivery in human ocular disease.