gms | German Medical Science

To explore neovascularization-related activities of cultured retinal endothelial cells in response to hypoxia, and their modulation by retinal glial (Müller) cells.

Bovine retinal endothelial cells (BRECs) were cultured under normoxia or hypoxia (0.5% O₂) either alone, together with the human Müller cell line MIO-M1, or in normoxia- or hypoxia-conditioned media of MIO-M1 cells. Cell number, proliferation, apoptotic cell death, and migration of BRECs were determined.

Exposure of BRECs to hypoxia for 24 h decreased the number of adherent cells and the proliferation rate but increased apoptosis and cell migration. Increased apoptosis of the BRECs occured also in the presence of conditioned media of MIO-M1 cells but not during co-culture with MIO-M1 cells. Under normoxic conditions, co-culture resulted in increased proliferation, but decreased the migration rates of BRECs. Under hypoxia, the presence of Müller cells decreased the proliferation and migration rates of BRECs.

Hypoxia inhibits the proliferation of retinal endothelial cells. Müller cells release soluble mediators that enhance this hypoxia-mediated effect but, under certain conditions (i.e., in co-culture), may protect retinal endothelial cells from apoptosis, thus supporting their survival. Whereas the key signal(s) necessary to trigger retinal endothelial proliferation under hypoxia remain(s) to be determined, our observations indicate that Müller cells may be effective in preventing retinal neovascularization.