Muller cell activation and remodeling in AMD.

Age-related macular degeneration (AMD) is a complex, multifactorial disease. I have recently reported subretinal Müller cell membranes in areas of geographic atrophy (GA). These membranes closely mimic areas of retinal pigment epithelial cells (RPE) and choriocapillaris loss. I have also observed Müller cells anterior to drusen expressing glial fibrillary acidic protein (GFAP) and appearing

to migrate to the ONL in eyes with AMD. These data indicate Müller cell activation and remodeling in AMD. The stimuli for and consequences of these changes, however, are not understood. We hypothesize that changes to the subretinal milieu in non-neovascular AMD stimulate Müller cell activation and remodeling that exacerbates AMD pathology.

The first Aim of this proposal will investigate how Müller cells are affected by subretinal changes that occur in AMD. We will investigate Müller cell morphological and metabolic changes anterior to drusen in human donor eyes with AMD. We will then evaluate the Müller cell response to drusen components,

amyloid beta and oxidized lipids, in vitro. The second subAim of Aim 1 will determine the effect that RPE cells exert on Müller cells. While these cells are normally separated by the photoreceptor segments, subretinal pathology as well as their abnormal migration and extension allows them to touch in eyes with AMD. We will analyze the RPE influence on Müller cells using human AMD tissue and cell

culture experiments. The second proposed Aim focuses on how Müller cells in the subretinal space affect neighboring cells. We will first investigate how Müller cells affect RPE cells using cell culture experiments. We will also investigate extracellular vesicle release by Müller cells and, if present, determine what effect these

have on RPE cells. We will also investigate the composition of the subretinal glial membranes that we have observed in GA. Since it is not possible to determine in human retinas how early in the disease process glia intrude the subretinal space, we have developed a rat model with focal RPE cell atrophy.

We will also determine whether these glial membranes form a scar which will prevent the flow of material, including future stem cell therapy, from the retina to subretinal space. Finally, we will inhibit the membrane and determine how this affects disease progression in our rat model of RPE atrophy.

These studies will determine the role glia play in AMD pathology, potentially identifying novel treatments. By investigating extracellular vesicle and exosome release from Müllers, our studies will identify how Müller cells interact with other cell types in the normal and diseased retina.