by Only about 600 people have ever traveled to space. The vast majority of astronauts over the past six decades have been middle-aged men on short-duration missions of less than 20 days.
Today, with private, commercial and multinational spaceflight providers and advertisers entering the market, we are looking at a new era of human spaceflight. Missions range from minutes, hours and days to months.
As mankind looks forward to returning to the Moon in the next decade, space exploration missions will be much longer, with many space travelers and even space tourists. This also means that a wider variety of people will experience the extreme environment of space – more women and people of different ethnicities, ages and health status.
Since people respond differently to the unique stressors and exposures of space, researchers in space health, like myself, seek to better understand the human health effects of spaceflight. With such information, we can figure out how to help astronauts stay healthy in space and when they return to Earth.
As part of NASA’s historic Twin Study, in 2019, my colleagues and I published groundbreaking research on how one year aboard the International Space Station affects the human body.
I am a radiation cancer biologist in the Department of Environmental and Radiological Health Sciences at the University of Colorado. In recent years I have continued to build on that earlier research in a series of papers recently published across the portfolio of Nature journals.
These papers are part of the Space Omics and Medical Atlas package of manuscripts, data, protocols and repositories representing the largest collection ever assembled for aerospace medicine and space biology. More than 100 institutions from 25 countries contributed to the coordinated release of a wide range of spaceflight data.
The NASA Twin Study
NASA’s Twin Study took advantage of a unique research opportunity.
NASA’s chosen astronaut Scott Kelly for the agency’s first year-long mission, in which he spent a year aboard the International Space Station from 2015 to 2016. Over the same period, his identical twin brother, Mark Kelly, was an astronaut and current United States senator who represents Arizona, stayed on Earth.
My team and I examined blood samples collected from the twin in space and their genetically matched twin on Earth before, during and after spaceflight. We discovered that Scott’s telomeres – the protective caps at the ends of chromosomes, like the plastic tip that keeps a shoe from slipping – grew longer, unexpectedly, during his year in space.
When Scott returned to Earth, however, his telomeres shortened rapidly. In the following months, his telomeres improved but were still shorter after his trip than before he went to space.
As you age, your telomeres shorten due to a variety of factors, including stress. The length of your telomeres can act as a biological indicator of your risk of developing age-related conditions such as dementia, cardiovascular disease and cancer.
In a separate study, my team studied a cohort of 10 astronauts on six-month missions aboard the International Space Station. We also had a control group of age- and sex-matched participants who remained on the ground.
We measured telomere length before, during and after spaceflight and again found that telomeres were longer during spaceflight and then shortened after returning to Earth. Overall, the astronauts had significantly more short telomeres after spaceflight than before.
One of the other Twin Study investigators, Christopher Mason, and I did another telomere study—this time with a few high-altitude mountain climbers—in a somewhat similar extreme environment on Earth.
We discovered that while climbing Mount Everest, the climbers’ telomeres were longer, and after their descent, their telomeres shortened. The twins who remained at low altitude did not have the same changes in telomere length. These results suggest that the microgravity of the space station was not the cause of the changes in telomere length we observed in the astronauts—another culprit, such as increased radiation exposure, is more likely.
A civilian in space
In our latest study, we studied telomeres from the crew aboard the SpaceX Inspiration 20214 mission. This mission, which lasted four decades, had the first civilian crew. All crew members’ telomeres lengthened during the mission, and three of the four astronauts also showed telomere shortening when they were back on Earth.
What is very interesting about these results is that the Inspiration4 mission only lasted three days. So not only do scientists now have consistent and reproducible data on the response of telomeres to spaceflight, but we also know that it happens quickly. These results suggest that even short trips, such as a weekend trip to space, will be associated with changes in telomere length.
Scientists still do not fully understand the health consequences of such changes in telomere length. We will need more research to determine how both short and long telomeres would affect an astronaut’s long-term health.
Telomeric RNA
In another paper, we showed that the Inspiration4 crew – as well as Scott Kelly and the high-altitude mountain climbers – showed elevated levels of telomeric RNA, called TERRA.
Telomeres consist of many repetitive DNA sequences. These are transcribed into TERRA, which contributes to telomere structure and helps them do their job.
Together with laboratory studies, these results inform us that telomeres are damaged during spaceflight. Although there is still much we do not know, we do know that telomeres are very sensitive to oxidative stress. Thus, it is likely that the chronic oxidative damage that astronauts experience while exposed to space radiation around the clock contributes to the telomeric responses we observe.
We also wrote a review article with a more futuristic perspective on how a better understanding of telomeres and aging knowledge could enable humans not only to survive long space travel but also to thrive and even colonize other planets. Doing so would require humans to reproduce in space and future generations to grow up in space. We don’t know if that’s even possible – yet.
Plant telomeres in space
My colleagues and I have also contributed other work to the Space Omics and Medical Atlas package, including a paper published in Nature Communications. The study team, led by Texas A&M biologist Dorothy Shippen and Ohio University biologist Sarah Wyatt, found that, unlike humans, plants flown in space during their time aboard the International Space Stations.
However, the plants increased their production of telomerase, the enzyme that helps maintain telomere length.
As anyone who has seen “The Martian” knows, plants will play an essential role in the long-term survival of humans in space. This finding suggests that plants may be naturally better suited to withstand spatial stresses than humans.
This article is republished from The Conversation, a non-profit, independent news organization that brings you facts and analysis to help you make sense of our complex world.
It was written by: Susan Bailey, Colorado State University.
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Susan Bailey receives funding from NASA.
