RPE Exosomes in Age-related Macular Degeneration

摘要

Abstract Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in the elderly in developed countries, and there are limited therapeutic options. The earliest clinical signs are lipid and protein deposits known as drusen, that form between the retinal pigmented epithelium (RPE) and the adjacent pentalaminar collagenous extracellular matrix, Bruch’s membrane. The RPE functions to maintain the outer blood-retinal barrier and to support photoreceptor function, including regeneration of visual pigment and turnover of outer segments. Dysfunction of the RPE underlies pathology leading to AMD. It is thought that in AMD this dysregulation in RPE cells is at least in part responsible for the formation of drusen. At present, the exact mechanisms for drusen formation are unknown. A potential approach to detect early AMD patho- biological changes is through the isolation of exosomes, which are nanovesicles that can be purified from biofluids (e.g. plasma and urine). Since RPE-released exosomes and other extracellular vesicles are essential parts of the endosomal pathway, I hypothesize that exosomes released from stressed RPE cells are distinct from those released from unstressed RPE cells, and that these exosomes are involved in the pathognomonic deposit formation and ECM changes that underlie the early and late stages of AMD. By evaluating two complementary in vitro and in vivo AMD models, our goal for this project is to determine the role of exosome secretion in sub-RPE deposit formation and in ECM changes under conditions relevant to AMD, and whether pharmacological or gene therapy/biological therapeutic interventions are possible. In the first aim, I will characterize and quantify the protein and lipid composition of sub-RPE deposits, ECM and basal- side exosomes in RPE stressed by pathophysiological conditions implicated in AMD (oxidative stress, complement dysregulation, and age), while modulating exosome release by both pharmacological and genetic approaches. In the second aim, I will molecularly tag, isolate and characterize RPE-derived exosomes from the blood of a well characterized mouse model of early-stage AMD. Detailed profiling of RPE-derived exosomes in normal and diseased settings represent novel studies that will provide insight into mechanisms that underlie pathobiological changes in AMD.