There are numerous risks associated with sending someone into space — it’s a completely foreign environment where even a small mistake can spell disaster. Our squishy Earth-bound bodies are so unaccustomed to space that simply being in microgravity can be dangerous long-term. The key to safer human space travel could be hiding inside these really buff mice. Scientists have found that blocking a protein in mice makes them resistant to muscle and bone wasting in space. Could humans be next?
The story actually starts 20 years ago when researchers at Johns Hopkins University discovered myostatin, a protein that limits muscle growth. Researchers Se-Jin Lee and Emily Germain-Lee showed at the time that deleting the gene caused mouse muscles to grow about twice as large. They speculated that manipulating myostatin could boost muscle mass in space. Currently, astronauts have to exercise with resistance equipment frequently to stave off the effects. Sending people to Mars with 37 percent Earth gravity would also lead to loss of muscle and bone, putting a kink in SpaceX CEO Elon Musk’s plans.
Lee finally had the chance to test this with a December cargo run to the International Space Station. Lee, now at the Jackson Laboratory for Genomic Medicine, sent 40 mice into space aboard the SpaceX CRS-19 mission. Of those mice, 24 were normal control animals, and eight were genetically modified to remove the myostatin gene. The remaining eight were treated with a compound that suppressed myostatin and a similar protein called activin A.
The team found that the normal mice lost significant muscle and bone mass. For a human, this would make reacclimating to Earth extremely difficult or impossible. The experimental animals without active myostatin showed notable improvements in muscles and bones. You can see in the image above how much larger these animals were after several months on the ISS compared with the control mice. Giving the myostatin inhibitor to mice after they returned from Space also helped them regain muscle mass.
Lee speculates that this could lead to treatments that help astronauts preserve muscle and bone mass during extended space missions. However, there’s a lot of work to be done first. It’s not feasible (or advisable) to modify an astronaut’s DNA before sending them into space. A molecule that could inhibit myostatin and activin A could be extremely helpful, but only after we’ve made sure it’s safe for humans. Such a drug could also be helpful in treating muscle wasting diseases like muscular dystrophy.
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