Proliferative activity and immunohistochemical cell differentiation in human epiretinal membranes.

Epiretinal membranes are a complex tissue mainly formed by the proliferation of retinal pigment epithelial cells, macrophages, glial cells, and fibroblasts. The proliferative contribution of these cells in regard of the formation of an epiretinal membrane is not yet clear. We determined the cellular proliferative activity by the use of the monoclonal antibody Ki-67 in 46 epiretinal membranes of proliferative vitreoretinopathy (PVR), PVR recurrences after intraocular silicone oil tamponade, proliferative diabetic retinopathy, and macular pucker. The proliferative activity of each membrane was indicated by the proliferative index (PI), which is the ratio of the actively proliferating Ki-67-positive cells and the total cell number in a cross-section of the membrane. The PI of each membrane was combined with the expression pattern of cell type associated antigens like cytokeratin for epithelial-like cells, KiM7 for macrophages, and glial fibrillary acidic protein for glial cells. Such a membrane typing revealed distinct interindividual differences, but no strict correlation with the underlying disease process. Our findings support the idea of an individual "fingerprint-like" membrane typing at the time of surgery combining the information about the antigen expression pattern of the participating cells and their functional proliferative state. Individual membrane typing for each patient might become clinically significant as soon as the dominating cells for tissue proliferation become key targets for specific pharmacological interventions.