Preliminary results of space experiment: Implications for the effects of space radiation and microgravity on survival and mutation induction in human cells

In view of the concern for the health of astronauts that may one day journey to Mars or the Moon, we investigated the effect that space radiation and microgravity might have on DNA damage and repair. We sent frozen human lymphoblastoid TK6 cells to the International Space Station where they were maintained under frozen conditions during a 134-day mission (14 November 2008 to 28 March 2009) except for an incubation period of 8 days under 1G or μG conditions in a CO₂ incubator. The incubation period started after 100 days during which the cells had been exposed to 54 mSv of space radiation. The incubated cells were then refrozen, returned to Earth, and compared to ground control samples for the determination of the influence of microgravity on cell survival and mutation induction. The results for both varied from experiment to experiment, yielding a large SD, but the μG sample results differed significantly from the 1G sample results for each of 2 experiments, with the mean ratio of μG to 1G being 0.55 for the concentration of viable cells and 0.59 for the fraction of thymidine kinase deficient (TK⁻) mutants. Among the mutants, non-loss of zygosity events (point mutations) were less frequent (31%) after μG incubation than after 1G incubation, which might be explained by the influence of μG on cellular metabolic or physiological function. Additional experiments are needed to clarify the effect of μG interferes on DNA repair.