The bait has another effect: it traps a second protein called Activin A, which also prevents muscle and bone growth. Sure enough, space mice injected with the decoy receptor had a twofold benefit: they kept their muscles polished and their bone density high. Bones and muscles even grew, so the treated mice with more of this tissue landed than untreated mice that were left on the ground.
The team also tested whether the treatments could reverse muscle and bone loss that had already occurred. To do this, they gave the decoy receptor to regular mice that had lost muscle and bone mass on the ISS after being splashed down in the Pacific on Jan. 7, 2020 and landing in San Diego. These animals quickly recovered from bones and muscles; Your muscles got even bigger than before the start.
The results suggest there might be a way to use a drug to protect astronauts from muscle and bone loss, says David Glass, vice president of research on aging and age-related disorders at Regeneron Pharmaceuticals in Tarrytown, New York. However, he warned that space atrophy is different from earth-based forms.
Still, Lee hopes that blockers for myostatin and activin A can maintain or restore the muscles in the floor. The physiologist Christoph Handschin from the University of Basel in Switzerland agrees, but adds a qualification: “That looks very promising – if this can be transferred to humans.” Handschin, who opposes the landscape of therapies in the Annual Review of Physiology Muscle wasting, notes that several drug companies have tried treating people with compounds that interfere with myostatin without much success.
However, Lee is optimistic. Suspecting that blocking myostatin is not enough in humans, he hopes that compounds like the deception receptor that activate activin A might prove to be more potent than previous compounds. Glass says that to avoid side effects, it would be important to develop a drug that is unlikely to interact with molecules other than myostatin and activin A as bait can.
And while helping human spaceflight isn’t Lee’s primary goal, such a molecule could potentially pique NASA’s interest as the agency plans longer space missions that likely won’t have room for bulky fitness equipment.
This article originally appeared in Knowable Magazine, an independent journalistic company owned by Annual Reviews. Sign up for the newsletter.