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Sarcopenia, which is a progressive and extensive decline in muscle mass and strength, is common with aging and is estimated to affect up to 50% of people aged 80 and older. It can lead to disability and injuries from falls and is associated with a lower quality of life and increased mortality. Apart from lifestyle changes, there is no current clinical treatment for sarcopenia.

Space flight with the associated absence of gravity and limited strain on muscles causes muscle weakness, a prominent feature of sarcopenia, within a short period of time, providing a time-lapse view on age-related atrophy-associated changes in the muscle. This relatively short window of time in space provides a microgravity model for muscular aging and opens opportunities for studying sarcopenia, which normally takes decades to develop in patients on Earth.

To understand the changes of muscle in microgravity, Siobhan Malany, Maddalena Parafati, and their team from the University of Florida, U.S., engineered skeletal muscle microtissues from donor biopsies and launched them to the International Space Station (ISS) aboard SpaceX CRS-25.

Their findings were in Stem Cell Reports.

The microtissues were taken from both young, active donors and from aged, sedentary donors and cultured in an automated mini-lab, which, besides regular feeding and monitoring of cultures, also enabled electrical stimulation to simulate exercise.

On Earth, the contraction strength of microtissues from young, active individuals was almost twice as much as the strength of tissues from older, sedentary individuals.

After only two weeks in space, muscle strength trended to decline in the young tissues and was now more comparable to the strength of old tissues. A similar trend was seen for the muscle protein content, which was higher in young microtissues on Earth compared to old microtissues but decreased in microgravity to levels measured in old tissues.

Further, space flight changed gene expression, particularly in the younger microtissues, and disturbed cellular processes related to normal muscle function. Interestingly, electrical stimulation could mitigate these changes in gene expression to some extent.

"Using electrical pulses to trigger real-time muscle contractions in space, we can simulate exercise and observe how it helps protect against rapid muscle weakening in microgravity," said Siobhan Malany, one of the lead researchers.

"This technology advancement offers insight into how we might preserve muscle health during long-duration space missions and, ultimately, how to combat age-related muscle loss here on Earth."

This study shows that sarcopenia-related muscle decline can be modeled within a relatively short period in space and paves the way for follow-up studies on causes and potential treatments for sarcopenia from aging or space travel.