NASA: Twins Study Proves a Year Living in Space a ‘Success’
Spending 340 days aboard the International Space Station between 2015 and 2016 caused changes in astronaut Scott Kelly’s body, from his weight down to his genes, according to the results of the NASA Twins Study, released last Thursday.
The majority of changes that occurred in Kelly’s body, compared with his identical brother, Mark, on Earth, returned to normal once he came back from the space station. The study results suggest that human health can be “mostly sustained” for a year in space, the researchers said.
On a call with reporters Thursday, Mark thanked Scott for his service to the country and commitment to science by spending a year in space without knowing how it would affect him.
“I got all the glory, and you got all the work,” Scott said, chiding his twin. “And I got people coming to my house for tubes of blood,” Mark replied in reference to the scientific samples taken during Scott’s mission; Scott was collecting the same samples from himself to send back to researchers on Earth.
The results show “the resilience and robustness of the human body,” said Steven Platts, deputy chief scientist for NASA’s Human Research Program, which coordinated the study.
Coincidentally, the results are being released just in time for the 58th anniversary of the first manned spaceflight by Soviet cosmonaut Yuri Gagarin.
But the much-anticipated study reveals areas that may require countermeasures or safeguards when preparing for longer space missions or missions to deep space, like Mars.
The molecular, physiological and behavioral changes were divided into low-, mid-level and high-risk groups. Scott’s change in body mass and microbiome were considered low-risk.
Shifts in collagen regulation and blood vessel fluid management were mid-level, and genomic instability was regarded as potentially high-risk.
“When we go into space and experience microgravity and travel at speeds like 17,500 miles an hour, our bodies adapt and continue to function and, by and large, function extremely well,” Platts said.
The study, which includes the work of 84 scientists who made up 10 teams from 12 universities in eight states, all studying different aspects of the human body in space, was published Thursday in the journal Science.
The data included cognitive measurements, physiological data and 27 months of samples from both brothers, including blood, plasma, urine and stool.
However, there are limiting factors to the study, the researchers said. The work is reflective of only Scott and Mark Kelly, and the results will not be corroborated with other astronauts, the researcher clarified. Scott was also still within the protective shield of Earth’s magnetic field on the space station, not bombarded by deep-space radiation.
“It is impossible to attribute causality to spaceflight versus a co-incidental event,” according to the study, so the researchers regard their work as “hypothesis-generating and framework-defining” that will benefit from more research in the future.
But they also believe it’s the “dawn of human genomics in space,” according toDr. Andy Feinberg, principal investigator and professor of medicine at the Johns Hopkins School of Medicine.
“The Twins Study has been an important step toward understanding epigenetics and gene expression in human spaceflight,” said J.D. Polk, chief health and medical officer at NASA Headquarters. “This has helped inform the need for personalized medicine and its role in keeping astronauts healthy during deep space exploration, as NASA goes forward to the Moon and journeys onward to Mars.”
Mark Kelly said he hopes it will happen in his lifetime. “I’d even volunteer to be the person to get to go now that we know this about my brother, Scott.”
But he’ll have to beat out his brother for that honor. “I’m ready to go. Put me on a two-year flight,” Scott said.
What changed in space
A year in space caused Scott’s carotid artery to thicken, DNA damage, gene expression changes, a thickening of the retina, shifts in gut microbes, reduced cognitive abilities and a structural change at the ends of chromosomes called telomeres. But it did not alter or mutate his DNA.
Getting a flu shot in space also worked exactly as it did on Earth. Nutrition and exercise while on the station caused weight loss and an increase in folic acid that caused the vital production of red blood cells.
The changes in gene expression were connected to DNA repair systems and the immune system. More than 1,000 genes changed as soon as Scott arrived in space. Some of the changes were expected, like those related to bone formation or repairing DNA, because astronauts lose bone density in space and radiation damages DNA.
But the changes to mitochondrial and immune system genes, which help produce energy and protect the body, suggest that long-term spaceflight increases stress on the body. There was also evidence of cellular stress.
This reveals that Scott’s immune system was on high alert in response to his environmental change, the researchers said.
“Gene expression changed dramatically,” said Christopher Mason, one of the study authors and associate professor of physiology and biophysics at Weill Cornell Medicine.
“While many of the changes reversed after Scott returned to Earth, a few remained, including cognitive deficits, DNA damage and some changes in T-cell activation. We don’t know yet if these changes are good or bad. This could just be how the body responds, but the genes are perturbed, so we want to see why and track them to see for how long.”
There was also a more dramatic change in genes during the last half of the mission compared with the first half, with six times the number of genes changing later.
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