EFFECT OF HYPOXIA ON THE PROLIFERATION OF RETINAL MICROVESSEL ENDOTHELIAL-CELLS IN CULTURE

Background: To determine if hypoxia stimulates the proliferation of re tinal microvessel endothelial cells in culture. Methods: Bovine retina l microvessel endothelial cells were cultured in normoxic (95% air, 5% CO2) and hypoxic (2% O-2, 5% CO2, 93% N-2) conditions, Endothelial ce lls were identified by acetylated LDL and Factor VIII-related antigen immunocytochemical staining, Cells from passages three to eight were u sed in these experiments, Proliferation assays included cell counts by hemocytometer and autoradiographic analysis of incorporated H-3-thymi dine (H-3-TdR). Results: At day 4, cell counts of endothelial cells in hypoxia showed a 133% increase over those grown in normoxic condition s (N = 25, P < 0.01), Cell counts per day for 5 days were 121-181% gre ater in hypoxia, Autoradiography of endothelial cells exposed to H-3-T dR and counted every 12 hours for 60 hours exhibited labeling indices 112-118% higher in hypoxic conditions (P < 0.0001), Endothelial cells cultured under hypoxic conditions were smaller and spindle-shaped, whe reas those grown under normoxic conditions were larger and more polygo nal, Conclusions: Hypoxia increases DNA synthesis and stimulates proli feration of retinal microvessel endothelial cells in vitro and induces alterations in morphology, These results may be relevant to microvess el angiogenesis, which occurs in vivo under ischemic conditions. (C) 1 997 Wiley-Liss, Inc.