Preservation of telomere length requires telomerase, the specialized reverse transcriptase capable of de novo addition of telomeric repeats onto the very ends of newly synthesized telomeres. Telomerase activity is prominent in highly proliferative cells like stem, germline, and cancer, but virtually absent in normal somatic cells. Changes in diet and lifestyle have been shown to modulate telomerase activity, with healthy lifestyles and diets being positively correlated with telomere length. It has been demonstrated that ionizing radiation also influences telomeres and telomerase. However, the relationships between telomere length and telomerase activity (measured in blood lymphocytes), lifestyle factors, and environmental exposures are largely unknown. The investigators speculate that for the astronauts, telomere maintenance represents a particularly relevant biomarker, as it reflects the combined exposures and experiences encountered during space travel. That is, an individual astronaut’s genetic susceptibilities, exposures to galactic space radiations, nutritional, physical, and psychological stressors encountered, are all captured as changes of telomere length maintenance; telomeres don't forget.
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.
|Mission||Launch/Start Date||Landing/End Date||Duration|
|Expedition 44||06/10/2015||09/11/2015||93 days|
|Expedition 45||09/11/2015||12/11/2015||91 days|
|Expedition 46||12/11/2015||03/02/2016||82 days|
|Expedition 47||03/02/2016||06/18/2016||108 days|
|Expedition 48||06/18/2016||09/06/2016||80 days|
|Expedition 49||09/06/2016||10/30/2016||54 days|
|Expedition 50||10/28/2016||04/09/2017||164 days|
|Expedition 51||04/09/2017||06/02/2017||55 days|
|Expedition 52||06/02/2017||09/02/2017||92 days|