A tale of two Kellys — NASA Twins Study

Jan Cross
April 14, 2019

There's the loss of muscle mass, for one thing. The overall takeaway, she said, is that the immune system is revved up under the stressors of space flight.

The "NASA Twins Study", published in the journal Science, monitored USA astronaut Scott Kelly, who spent a year on the International Space Station, and his earthbound identical twin Mark Kelly, also a former astronaut.

The NASA study was published this week in the journal Science.

What happens to your body when you live in space?

But after monitoring the differences between a pair of identical twins as one traveled to the International Space Station and the other stayed on Earth, researchers say there's more work to be done to understand how long-term space travel can affect a person's body.

In an image provided by NASA, Astronaut Scott Kelly gives himself a flu shot aboard the International Space Station, Sept. 24, 2015.

As for trips to Mars, Mark Kelly said: "I hope it's sooner rather than later, and hopefully, our participation in this study will help us get closer to making a mission like that a success".

Some of the most important medical experiments involved cardiovascular health. Mark underwent identical tests. But that's no fountain of youth, the study found, because the telomeres shortened dramatically when he returned to Earth.

There was also a spike in circulating markers of inflammation, especially so called c-reactive proteins (CRP), which are predictive of cardiovascular problems.

In the current study, Scott's biological samples were shipped back to Earth immediately, but in the future, astronauts may need to process and store samples on the spacecraft. His immune system produced a host of new signals.

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The good news was, Kelly's immune profile returned more or less to baseline after he came home.

Next, Kelly's DNA wasn't mutated in space but the activity of many of his genes - how they switch on and off - did change, especially in the last half of the voyage, which ended in March 2016. "They included things that affect DNA maintenance and fix, as well ramping up the immune system when it's needed". For example, the makeup of Scott's gut microbiome shifted, perhaps due to a change in diet, and then shifted back after his flight. Not all of the changes disappeared-or at least not quickly-after Scott's return.

To study the twins' telomeres, Bailey and her team received vials of their blood over 25 months, spanning time points before, during and after spaceflight.

Bailey's team evaluated Scott and Mark's telomere lengths before the flight and found that they were very similar. Surprisingly, it seems that space is somehow protective against telomere shortening, which could help determine the risks and benefits of long-duration spaceflight. The unusual lengthening of Kelly's telomeres disappeared after less than 48 hours on Earth. That's an effect researchers on Earth have tried to achieve with telomerase, an enzyme that sustains and builds telomeres. If we had hundreds of identical twins, would we see that same result? "We're seeking correlations that can explain how this is happening".

"Do not think of telomere lengthening as a fountain of youth", warns Bailey.

A number of key findings have been detailed in NASA's study, including information about the effects space had on Scott Kelly's telomeres.

Editor's note: Susan Bailey, a professor in the Department of Environmental and Radiological Health Sciences, wrote this piece for The Conversation in April 2019.

The locations of methylation changes in the genome were different for each twin. After a month I felt mostly better.

While in space, researchers observed changes in the expression of Scott's genes, with the majority returning to normal after six months on Earth.

-Kelly aced cognitive tests in space but slowed down after his return, maybe as more things competed for his attention. Another enduring change, scientists found, was a collection of genetic mutations that Kelly gained in space. Kelly's near-year is the record for an American. "Yet, 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 really well". But what about the human body's response to real-life spaceflight - what are the health effects?

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