AILSA CHANG, HOST:
And now an update on some muscular mice who spent a month on the International Space Station. NPR's Jon Hamilton reports that these mousetronauts (ph) were part of an experiment that may show how humans can stay strong during interplanetary voyages.
JON HAMILTON, BYLINE: Without Earth's gravity, muscles and bones can get weak fast, so astronauts on the space station spent two hours a day exercising. Back in April, Jessica Meir and Drew Morgan even made a weightless workout video.
(SOUNDBITE OF ARCHIVED RECORDING)
DREW MORGAN: This next exercise is cardiovascular exercises - T2, treadmill two. Bungees and my harness are holding me against the treadmill.
JESSICA MEIR: It's pretty fun to run on the T2. You get a little bit of an extra spring in your step.
HAMILTON: Intense exercise reduces bone and muscle loss but doesn't stop it, and that's a problem if you're headed for, say, Mars. So in December, researchers sent some very special mice into orbit.
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UNIDENTIFIED GROUP: Five, four, three, two, one.
UNIDENTIFIED PERSON: And (unintelligible).
HAMILTON: Some of the mice were just along for the ride. Others got injections of a drug that inactivates two substances that occur naturally in the body. They're called myostatin and Activin-A, and normally, their job is to limit the growth of muscle and bone. Dr. Se-Jin Lee of the Jackson Laboratory says when they reached the space station, all the mice got lots of exercise.
SE-JIN LEE: Once they get up there, they become very active. And in fact, they have a name for it - racetracking (ph) - because they're, you know, running around quite a bit.
HAMILTON: After a month in orbit, the mice splashed down off the California coast and were rushed to a lab in San Diego. Lee says normal mice that did not receive any treatment lost more than 10% of their muscle mass, and he says bone loss was an even bigger problem.
LEE: They lost a substantial amount of bone in space. And then even after being on earth, they actually continued to lose a little bit more bone mass.
HAMILTON: Lee says the mice that got the drug did much better.
LEE: The drug was effective not just in preserving the muscle mass and bone mass that was being lost but actually caused the muscles and bones to grow.
HAMILTON: The drug also reversed muscle and bone loss in mice that got it after they returned to Earth. Dr. Emily Germain-Lee of the University of Connecticut says a human version of the drug could help both astronauts in space and millions of people on Earth.
EMILY GERMAIN-LEE: That would be a miracle for a person either with primary bone disease, primary muscle disease or a combination.
HAMILTON: But Germain-Lee, who is married to Se-Jin Lee, cautions that so far, the treatment has only worked in mice.
GERMAIN-LEE: They had a phenomenal response to the drug without, apparently, any bad side effects. That's not necessarily something that we could extrapolate to humans.
HAMILTON: But she's hopeful and says experiments on people are underway. The research appears in the journal Proceedings of the National Academy of Sciences.
Jon Hamilton, NPR News.
(SOUNDBITE OF BLOCKHEAD SONG, "FAREWELL SPACEMAN") Transcript provided by NPR, Copyright NPR.
