Age-related macular degeneration (AMD) is a complex, multifactorial disease. I have recently reported subretinal Mller 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 Mller cells anterior to drusen expressing glial fibrillary acidic protein (GFAP) and appearing to migrate to the ONL in eyes with AMD. These data indicate Mller 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 Mller cell activation and remodeling that exacerbates AMD pathology.
The first Aim of this proposal will investigate how Mller cells are affected by subretinal changes that occur in AMD. We will investigate Mller cell morphological and metabolic changes anterior to drusen in human donor eyes with AMD. We will then evaluate the Mller 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 Mller 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 Mller cells using human AMD tissue and cell culture experiments. The second proposed Aim focuses on how Mller cells in the subretinal space affect neighboring cells. We will first investigate how Mller cells affect RPE cells using cell culture experiments. We will also investigate extracellular vesicle release by Mller 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 Mllers, our studies will identify how Mller cells interact with other cell types in the normal and diseased retina.
This study will breach a gap in knowledge regarding the role Mller cells, the primary glial cell in retina, play in non-neovascular AMD pathology. This study will also identify what stimulates Mller cell migration and proliferation leading to subretinal membrane formation, which we have reported in eyes with geographic atrophy. By looking at how Mller cell changes in AMD affect other cells, including retinal pigment epithelial cells, these studies may identify novel therapeutic targets for treating AMD.
