cis-Hydroxyproline inhibits proliferation, collagen synthesis, attachment, and migration of cultured bovine retinal pigment epithelial cells.

PURPOSE Proliferative vitreoretinopathy (PVR) is characterized by the proliferation and migration of retinal pigment epithelial (RPE) and other cells into the vitreous cavity. The PVR membrane formation also is associated with collagen production by RPE. The authors examined the effect of a proline analog, cis-hydroxyproline (CHP), on proliferation, collagen synthesis, attachment, and migration of bovine RPE in vitro. METHODS The effect of CHP on cell proliferation was determined as a function of dosage and days in culture by counting the cell numbers on days 3, 6, and 9. Collagen synthesis was determined by trichloroacetic acid precipitation of the radiolabeled samples before and after bacterial collagenase digestion. The attachment assay involved type I collagen or fibronectin substrates or both (2.5 micrograms/well). For migration experiments, RPE cells were removed from a defined area of a confluent culture, and migration was quantitated by counting the number of cells migrating into the denuded area over 30 hours. RESULTS The addition of CHP inhibited RPE proliferation in both a dose- and a time-dependent manner; collagen synthesis, attachment, and migration also were inhibited by CHP in a dose-dependent manner. When the culture plates were coated with collagen, < 100 micrograms/ml of CHP had no effect on cell attachment. Higher doses of CHP resulted in mild inhibition of attachment on collagen-coated plates. Simultaneous addition of L-proline to the cultures resulted in blockade of these inhibitory effects on proliferation, collagen synthesis, attachment, and migration. CONCLUSIONS The results show that RPE functions critical to the development of PVR are inhibited by CHP, suggesting the possibility that this drug may have potential clinical application.