The aim of this project is to perfect a procedure for the culture of retinal microvessel pericytes and endothelial cells from a single pair of human eyes. The procedure will employ a technique already in use in our laboratory that permits retinal microvessels to attach to the surface of a culture dish and spread into colonies of endothelial cells and isolated pericytes. The establishment of pure replicating cultures will depend on the resolution of two problems: a) elimination of unwanted cell types from the culture and (b) promotion of the growth of the cell type of interest. The procedures we will test for the elimination of unwanted cell types will include physical removal and selective growth conditions. We will test several culture conditions for their effect on the growth of endothelial cells and pericytes: different substrates, different concentrations of serum or plasma, specific growth factors, and various cell or tissue extracts. The characterization of the cells will include: the presence of factor VIII antigen, the presence of angiotensin-converting enzyme activity and a specific ultrastructural marker. Once established the cultures will be useful in studies to determine the possible cause of disorders involving retinal neovascularization, including diabetic retinopathy.