Simulated microgravity induced damage in human retinal pigment epithelial cells.

PURPOSE The goal of this study was to determine the potential damage to the human retina that may occur from weightlessness during space flight using simulated microgravity. METHODS Human retinal pigment epithelial (hRPE) cells were cultured for 24 h in a National Aeronautics and Space Administration-designed rotating wall bioreactor vessel to mimic the microgravity environment of space. Single-stranded breaks in hRPE DNA induced by simulated gravity were measured using the comet assay. In addition, the production of the inflammatory mediator prostaglandin E2 (PGE2) was measured in these cells 48 h after recovery from simulated microgravity exposure. RESULTS Simulated microgravity induced single-stranded breaks in the hRPE DNA that were not repaired within 48 h. Furthermore, PG E2 production was dramatically increased 48 h after the initial microgravity-induced damage, indicating the induction of an inflammatory response. There was less DNA damage and no PGE2 release in hRPE cells pretreated with the antiinflammatory agent cysteine during their exposure to microgravity. CONCLUSIONS We have demonstrated that the microgravity environment generated by a NASA-designed rotating wall bioreactor vessel induces an inflammatory response in hRPE cells. This system thus constitutes a new model system for the study of inflammation in the retina, a system that does not involve the introduction of an exogenous chemical agent or supplementary irradiation. This in vitro method may also be useful for testing novel therapeutic approaches for suppression of retinal inflammation. Furthermore, we suggest a safe prophylactic treatment for prevention of acute, transitory, or enhanced age-related permanent blindness in astronauts or flight personnel engaged in long-haul flights.