As people age, they gradually lose muscle mass and strength because of a condition called sarcopenia, which typically takes decades to progress. For astronauts in space, however, microgravity, or weightlessness, causes them to experience extreme muscle weakness over a significantly shorter period of time.
To test whether microgravity can be a tool to better understand sarcopenia, a team of Stanford Medicine researchers sent engineered muscle tissue to the International Space Station. If the experiment works, scientists will be able to rapidly assess potential drugs that diminish muscle loss in advance of launching treatment clinical trials. The tissue was launched into space on Aug. 10.
"If one were to try to develop a drug to treat sarcopenia on Earth, that would be really hard because it would take decades to study the efficacy in patients," said Ngan F. Huang, PhD, assistant professor of cardiothoracic surgery and principal investigator of this study, which is funded by the National Science Foundation and the Center for the Advancement of Science in Space. "Microgravity has been shown, in a lot of contexts, to accelerate a lot of different diseases. We thought: 'Well, maybe microgravity could be a way to accelerate the process of sarcopenia.'"
The condition primarily impacts people who are 60 or older, accelerating mobility problems, falls and fractures. It is estimated that about 10% of the global population suffers from sarcopenia, and the prevalence approaches 50% for individuals older than 80. As the global aging population is expected to double by 2050, developing treatments for sarcopenia becomes increasingly important.
Tracking how negative gravity affects aging tissue
To create the engineered tissue, Huang and her colleagues layered human muscle cells onto scaffolding made from collagen, a structural protein found in hard and soft tissues. The cells fuse into organized strips of myotubes, or primitive muscle fibers.
As the muscle cells grow and mature, astronauts onboard the space station will collect microscopic images and tissue samples from them.
The astronauts will also test whether two drugs that have been shown to induce the formation of myotubes work efficiently in microgravity. This could allow scientists to identify therapeutics for sarcopenic patients on Earth and for astronauts during long space missions.
After seven days in space, the engineered tissue will be sent back to Earth. Its genetic signature will then be analyzed to see if it matches that of sarcopenia. Huang's team will also examine whether the muscle cells that didn't receive any drugs struggled to form new myotubes.
"Based on what we know from other works and from the astronauts themselves, we think microgravity will simulate muscle atrophy," said Huang. "If it works, this platform could be used to identify drugs over the course of a week or two."
Photo courtesy of Palo Alto Veterans Institute for Research/NASA