Effects of retinal glial cells on isolated rat retinal ganglion cells

PURPOSE. The effect of retinal glial cells on retinal ganglion cell (RGC) s urvival was investigated in cocultures of pure, isolated retinal glial cell s with pure, isolated RGCs. METHODS. RGCs from 2-day-old rats were cocultured for 48 hours, avoiding di rect contact between cell types, with either nonconfluent retinal glial cel ls from 3-day-old rats or confluent retinal glial cells from 3-day-old, 12- day-old, or 1-year-old rats. Survival of RGCs was evaluated by flow cytomet ry. Amino acids were determined in culture medium. The effects of glutamate antagonists, 6-cyano-7-nitroquinoxaline-2,3-dione and MK801, a nitric oxid e (NO) scavenger, 2-(4-carboxyphenyl)-4,4,5,5tetramethylimidazoline-1-oxyl- 3-oxide potassium salt (c-PTIO), and an NO synthase inhibitor, NG-nitro-L-a rginine methyl ester (L-NAME), were examined. RESULTS. Nonconfluent retinal glial cells significantly reduced the surviva l of small and large RGCs, but confluent retinal glial cells reduced the su rvival of only small RGCs, regardless of the rat's age at the time of retin al glial cell harvesting. Profiles of some amino acids significantly varied , depending on the culture condition. Cocultures of RGCs with nonconfluent retinal glial cells released significantly more glutamate into the medium t han cocultures of RGCs with confluent retinal glial cells or RGCs in pure c ulture. The glutamate antagonists improved the survival of RGCs cocultured with nonconfluent retinal glial cells, especially when the two were adminis tered in combination, and in the case of large RGCs. c-PTIO and L-NAME, als o improved the survival of RGCs cocultured with nonconfluent retinal glial cells. CONCLUSIONS. Adverse effects of retinal glial cells on the survival of RGCs varied by size of the RGCs and retinal glial cell confluence. Glutamate an d NO may be involved in retinal glial cell-related antisurvival effects.