Mice in Space Showed Liver Damage After Two Weeks
The finding raises concern about what long-duration spaceflight might do to humans.
Lab mice that spent just two weeks in orbit showed early signs of liver damage upon returning to Earth, raising concern about what long-duration spaceflight might do to humans, researchers said Wednesday.
The findings could interest the US space agency, which plans to send people to deep space destinations such as an asteroid or Mars by the 2030s - missions that will require long stays in space.
NASA is already studying the effects of long-term spaceflight on the human body, and recently sent one of its veteran astronauts, Scott Kelly, on a 340-day stay at the orbiting International Space Station, a mission that also included a Russian cosmonaut.
"Prior to this study we really didn't have much information on the impact of spaceflight on the liver," said lead author Karen Jonscher, an associate professor of anesthesiology and a physicist at the University of Colorado's Anschutz Medical Campus.
"We knew that astronauts often returned with diabetes-like symptoms but they usually resolved quickly."
The mice spent 13 and a half days aboard the space shuttle Atlantis in 2011.
Once back on Earth, researchers found that spaceflight appeared to trigger certain cells that may cause scarring and long-term organ damage.
Namely, the mice showed increased fat storage in their livers, as well as a loss of retinol, an animal form of Vitamin A.
They also showed changes in their ability to break down fats, and showed signs of nonalcoholic fatty liver disease "and potential early indicators for the beginnings of fibrosis, which can be one of the more progressive consequences of NAFLD," said the study.
Researchers already know that spaceflight can cause a loss of bone and muscle mass, as well as changes in vision and brain function in people.
Jonscher said the signs of liver damage they saw in mice would typically take months to years to develop by eating an unhealthy diet.
"If a mouse is showing nascent signs of fibrosis without a change in diet after 13.5 days, what is happening to the humans?" she asked.
The findings were published in the journal PLOS ONE.
NASA did not immediately respond to a request for comment.
"Whether or not this is a problem is an open question," Jonscher said.
One possibility is that the stress of spaceflight, particularly the jiggling, noise and commotion on departing and re-entering Earth's atmosphere, contributed to the liver damage.
Further study on the tissues of mice flown at the International Space Station for months could shed more light on whether microgravity plays a role in liver damage.
"We need to look at mice involved in longer duration space flight to see if there are compensatory mechanisms that come into play that might protect them from serious damage," Jonscher said.
Scott Kelly is a NASA astronaut working for a year in space on the International Space Station. Does he have the stuff of "The Martian,"
, chronicling the life of a stranded astronaut on the surface of Mars? While Kelly certainly isn't on his own in space, much of the work he is doing would be useful for a trip to Mars. Here are some of the things the astronaut is working on that Mark Watney (Damon's character in "The Martian") would appreciate.
The sun goes through an 11-year cycle of activity, and we are just past the peak of one of those cycles. The solar peak is a time when the sun unleashes more flares and coronal mass ejections (charged particles). When these particles hit the Earth's magnetic field, they can produce spectacular auroras.
The space station monitors radiation levels for astronauts close to Earth; in fact, one of the reasons Kelly was selected for this mission was he did not exceed the lifetime radiation levels allowed for astronauts. Radiation is expected to jump for those travelling outside of Earth's magnetic influence. Mars doesn't have much magnetic field to speak of, and the Curiosity mission is monitoring radiation levels on the surface to get more information for future human missions.
Working in space is a harsh business. You're busy all the time, you're stuck in a small environment with several people, and your family and friends are far away. NASA keeps close tabs on its astronauts' psychological health through measures such as doctor calls with astronauts, and
during their missions. This will especially be important for Mars, as astronauts will need to be even more self-sufficient due to the time delay in communications between planets. NASA has
for astronauts doing simple tasks; these tasks and their effects on astronauts will be studied as the station work continues.
Microgravity is hard on your body. NASA has its astronauts exercise for a couple of hours a day, which seems to help counteract bone loss for missions of six months. But what about a year, or longer? That's part of what Kelly's mission is supposed to answer. Bones aren't the only things to worry about, either. Muscles shrink, eye pressure increases, your sense of balance changes. Even your immune system may be affected, something that
in detail. So while we think of astronauts as boldly doing spacewalks and experiments on station, understand that they are also part of the experiment. Their very health is being watched for the benefit of future space missions.
While Watney develops a certain affection for potatoes, Kelly recently posted a picture of himself looking pretty pleased next to a floating pile of fruit. It turns out that little comforts do go a long way for astronaut morale, and any nutritionist would tell you that a varied diet of healthy foods is good for you -- not just the freeze-dried stuff the Apollo astronauts survived on during their missions. NASA has an experiment in place to see how well
, and also for their long-term health.
Astronauts are very tied to shipments from Earth right now in terms of eating ... but that is changing in a small way.
, astronauts got to taste some food grown aboard the space station this summer. Lettuce, of course, does not an entire meal make. But as the movie Contact (1997) reminds us, it's through "small moves" that we learn about science. The hope is eventually this experiment will translate into a better way of harvesting crops beyond Earth. For Mars, we're even wondering how viable the soil could be to support plants.
"#ILookLikeAnEngineer on @space_station. Also a scientist, medical officer, farmer & at times a plumber," Kelly wrote with this image in August. What's more, he has to do all those things in a small space. Since every pound hoisted to space costs money, astronauts are accustomed to working in claustrophobic quarters. But NASA, concerned about its astronauts' efficiency and happiness, also has an
. That way, the habitats designed for Mars will be suitable for long-term living.
During a recent Twitter chat, Kelly was asked if he wanted to go to Mars. He said yes, as long as he could return. Getting to Mars and back will take hundreds of days of transportation, let alone the time on the surface. The gravity on Mars is less than 40% what we experience here on Earth. And unless spacecraft design changes substantially, the astronauts will be in microgravity on the way there and back. NASA has an experiment to see
, an experiment that Kelly is participating in. This will be important not only for returning to Earth, but seeing how well a crew can get adapted to Mars after being in microgravity for the transit.