Glaucoma is a blinding eye condition in which elevated intraocular pressure (IOP) is associated with visual impairment. For most cases of glaucoma, including primary open angle glaucoma and a number of secondary glaucomas, the increase in IOP is related to a decrease in the ability of aqueous humor to flow through the trabecular meshwork. The role of the trabecular endothelium in these conditions has not been clarified. A major problem has been the lack of a system in vitro in which the characteristics of trabecular meshwork cells can be studied. Recently, we have propagated trabecular endothelial cells from both human and monkey sources in continuous culture. The cells have unique properties that distinguish them from other endothelial cells and from neighboring eye cells. In addition, trabecular meshwork cells in vitro: 1) produce hyaluronic acid and other connective tissue elements similar to intact tissue; 2) have structural and cytological features similar to intact tissue; 3) demonstrate active phagocytic properties; and 4) have glucocorticoid receptors and respond to physiological levels of hormone. In the current proposal we hope to examine further the biological properties of cultured trabecular endothelial cells. Initial efforts will be directed at establishing conditions for optimal cell growth. Particular emphasis will be given to a detailed investigation of the differentiated functions, such as glycosaminoglycan (especially hyaluronic acid) metabolism and phagocytic activity, which may have a potential pathogenic role in glaucoma. It is hoped that these studies will provide a better bases for understanding the function of trabecular endothelium, and its relation to trabecular meshwork, in physiologic and disease states. It is also hoped that the information gained will facilitate new therapeutic approaches for the treatment of primary open angle glaucoma and some secondary glaucomas.