NASA twins study explores space, the final genetic frontier

Mark and Scott Kelly

Mark and Scott Kelly

After almost a year in space, Kelly looked pale but appeared alright, joking about the weather with the crew and media.

But key results from the NASA Twins Study do confirm that prolonged space travel triggers stressors that can alter genes, send the immune system into overdrive, or hinder mental reasoning abilities and memory. Results will guide future studies and personalized approaches for evaluating health effects of individual astronauts for years to come.

By comparing the two men, who share the same genes, researchers were able to see - down to the DNA - what changed as Scott endured the stresses of space travel.

"We looked at a panel of 62 cytokines and saw that 50 of them were changing in some manner associated with flight, about half of which were elevated", said Tejaswini Mishra, PhD, a postdoctoral scholar at Stanford and one of the study's lead authors.

But the scope of the new study went far beyond just aging.

Yet this study comes with a big, big caveat. In 2015, Kelly rode a rocket into space and spent almost a year on the International Space Station in low Earth orbit, while his identical twin brother, Mark Kelly, stayed on Earth's surface for NASA's celebrated "twins study", created to see what spaceflight does to the human body. But Scott Kelly says he's actually a few milliseconds younger still, due to having spent 500 more days in space than his astronaut brother. But perhaps, during a longer deep space mission, this could lead to ill-effects. Remarkably, the Kelly twins were individuals of similar "nature (genetics) and nurture (environment)", and so the flawless space experiment was conceived - featuring "space twin and Earth twin" as the stars. That's the question that NASA set out to answer - with twins.

More than 300 biological samples - stool, urine and blood - were collected from the twins at multiple times before, during and after the one year mission. Importantly, his genes never mutated. Among the genes with altered activity, 9 percent remained abnormal.

A flu vaccine administered in space worked exactly as it would on Earth, indicating that the immune system is not significantly compromised outside the planet.

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"Although average telomere length, global gene expression, and microbiome changes returned to near preflight levels within 6 months after return to Earth, increased numbers of short telomeres were observed and expression of some genes was still disrupted", the report states. Both categories contain a mix of both good and bad bacteria. But it comes with a slew of well-known limitations. Technological hurdles are only one aspects of this goal, though - the space agency needs data on how time spent in space impacts the human body.

Kelly and Kornienko left Earth for the space station in March 2015 and returned in March 2016.

The intensive scrutiny of Kelly's body revealed a lot, but there's only compelling evidence for one human: Kelly. "It just tells us that we need to be monitoring the astronauts when they come back". "The Twins Study demonstrated on the molecular level the resilience and robustness of how one human body adapted to the spaceflight environment", said Jenn Fogarty, chief scientist for NASA's Human Research Program.

Space presents unique stresses to the human body.

Nevertheless, the findings point to issues that will have to be resolved as NASA plans for trips beyond Earth orbit, to the moon, Mars and beyond. The changes affect when and how a gene is expressed for its protein-encoding instructions. Vision, not surprisingly, suffers in space, though again, signs of these so-called neuro-ocular changes largely abated when Kelly got home.

Though, decades of research have shown that some astronauts do experience clear physical problems after living in space. These changes typically affect visual acuity and, says Feinberg, have occurred in other male astronauts but not females. Astronauts have also experienced an increase in the stiffness of blood vessels, but it's unknown if that's something that could result in heart disease.

The researchers cautioned against reading too much into their study. "We're nowhere near that now".

NASA already knew some of the toll of space travel, such as bone loss that requires exercise to counter. "But the findings give us clues to what we should examine more closely in future studies of astronauts".

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