RESULTS:
Astronauts in general tended to have shorter telomeres at baseline than healthy age/gender matched ground control subjects. They also tended to have lower levels of telomerase activity than ground control subjects. Unfortunately, telomerase activity was “lost in space” for all of inflight samples, likely due to unavoidable transit time and/or conditions (e.g., temperature) during return via Soyuz from the International Space Station (ISS) and then to Johnson Space Center (JSC). Most striking was the observation of significantly longer telomeres of crewmembers who spent six months on the ISS. Astronauts in general tended to have shorter telomeres after flight than they did before. Upon return to Earth, average telomere length shortened rapidly (by the R+7 timepoint).

Cell by cell analyses by Telo-FISH and generation of individual telomere length distributions revealed dramatic shifts in the shortest and longest telomere populations, consistent with the observed changes in average telomere length. Results further supported chromosomal inversions as informative biomarkers or “signatures” of space radiation exposure, and were suggestive of persistent genome instability post flight; i.e., frequencies remained elevated. Evidence of telomere replication stress and recombination were also observed during space flight.