We've always been seeing news about how we've been sending people to space and gathering endless data but we see very less of news about how these people are fairing in space and when they're back on earth. In a recent video, NASA astronaut Andrew Feustel after 197 days in space took his first steps on earth and he faltered. Weightlessness does this to the body. When astronauts spend extended time in space, the lack of gravity leads to losses in bone density and muscle mass.
NASA has rehabilitation programs that help astronauts recover upon returning to Earth, but Marni Boppart, Ph.D., the new paper's first author and an associate professor at the University of Illinois Beckman Institute, believes that she's found a way to combat muscle loss through muscular injections of pericytes.
Pericytes are found around the blood vessels in the muscles of both humans and mice, and when muscles aren't active, pericytes degrade and muscle mass declines. In her experiment, Boppart watched the muscle fibers and pericytes decline in tandem: Mice whose hind limbs were immobilized for 14 days lost these cells and muscle fibers at a rapid rate compared to mice that were allowed to wander freely. A similar phenomenon happens when our muscles atrophywhen they're not used. Just think about the muscle loss that happens while a limb is immobilized in a cast.
Recovering lost muscle takes time, energy, and the slow process of physical therapy. But Boppart's strategy speeds things up considerably. When the team re-injected populations of pericytes back into mice starting their own muscle recovery process, they found that the injections made a huge difference. By the end of just two weeks, the mice who received injections had completely recovered, whereas control mice still had significantly reduced muscle mass.
"We decided based on that finding that we could potentially transplant these cells to replace the pericyte loss, and that would help with the recovery process," says Boppart. "What we found was in fact that the perricyte injection was very beneficial in enhancing the recovery of muscle."
Boppart thinks that pericytes do more than just replace lost muscle cells. She believes that they excrete extracellular vesicles - tiny packages that cells sometimes use to communicate - of therapeutic agents that stimulate the regrowth of muscle and, crucially, the regrowth of capillaries, the vessels that deliver oxygen-rich blood to muscles.
"We know that these cells are very beneficial," she says. "But when we're thinking about our future studies we're hoping to actually extract the important regenerative materials from these cells. So what we're hoping to do is to extract the extracellular vesicles secreted by the pericytes in the blood stream, and hopefully inject those derived from a person, back into that same individual."
Going forward in human studies, her work will likely focus on mining the riches of and developing a personalized muscle-restoration injection that, in combination with exercise, will help restore muscle. Ideally, these injections should greatly reduce the time it takes human astronauts to reacclimatize to life on their home planet, and perhaps even help people who have spent months recuperating in casts or in hospital beds get back up to full speed.
