Scientists have uncovered why astronauts lose body mass during extended stays in space. A new study conducted on the International Space Station (ISS) and in ground-based laboratories has identified the molecular mechanism behind this phenomenon.
Prolonged time in space leads to muscle atrophy and reduced bone density. Researchers have long sought the cellular roots of these processes. It turns out that the absence of gravity disrupts the function of mitochondria—the energy powerhouses of cells.
Research in space biology holds significance for medicine on Earth. The discovery of how cells deteriorate in weightlessness opens up avenues for combating sarcopenia—age-related skeletal muscle atrophy that causes strength loss in older adults. Understanding how mechanical cell adhesion regulates mitochondria could aid in developing drugs that slow aging and support the health of bedridden patients.
On the International Space Station, mitochondria in human and worm cells produce significantly fewer proteins. Previous scientific data already indicated that space flights damage mitochondria and affect the transcription of DNA into messenger RNA (mRNA).
In this new study, a Japanese team from the RIKEN institute, led by molecular biologist Shintaro Iwasaki and published in the journal Nature Communications, focused on the translation process—the stage where ribosomes synthesize proteins based on mRNA.
Experiments conducted by astronauts in orbit with human cell cultures revealed a marked decrease in mitochondrial protein synthesis within just 24 hours of weightlessness. Control samples spun in a centrifuge to simulate Earth’s gravity showed no such changes.
Similar results emerged from studies of Caenorhabditis elegans worm larvae exposed to weightlessness for four days. Follow-up experiments on Earth using a clinostat—a device that mimics reduced gravity by rotating cells—confirmed this pattern. After 24 hours of operation, human cells produced 13 fewer mitochondrial proteins, and extending the experiment to three days further intensified this effect.
Space biologist Thomas Corydon from Aarhus University in Denmark noted that it is well known that microgravity reduces or alters gene expression. However, this analysis is the first to clearly demonstrate how the absence of gravity directly impacts cells at the protein level.
To understand the causes of this phenomenon, researchers examined cell adhesion—the ability of cells to bind to each other in tissues via surface proteins. They discovered that it is precisely the disruption of mechanical cell adhesion forces in weightlessness that triggers negative changes in mitochondria.
When the authors treated cells with specialized proteins that support adhesion before placing them in the clinostat, mitochondrial protein synthesis returned to normal. Conversely, substances that interfere with cell adhesion completely blocked mitochondrial translation and reduced oxygen consumption.
Shintaro Iwasaki’s team now plans to continue searching for chemical compounds and drugs capable of activating translation in mitochondria. This could not only help develop effective measures to protect astronaut health during deep-space missions but also open new approaches to treating age-related diseases on Earth.
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