Human blood-forming stem cells age more rapidly during spaceflight, accumulating damage linked to cellular ageing and impaired regeneration, A new study has found. The experiment involved human hematopoietic stem and progenitor cells sent aboard a SpaceX Dragon capsule to the International Space Station, where they spent about a month before returning for analysis. Over that period, the cells lost their capacity for healthy renewal, showed DNA wear, possibly affecting immune function, and developed features that may predispose them to cancer.
Molecular Wear in Space
Researchers at UC San Diego, who conducted the experiment, found that hematopoietic stem and progenitor cells exposed to microgravity lost key self-renewal capabilities and exhibited telomere shortening, DNA damage, and mitochondrial stress. The pattern mirrors mutational signatures associated with clonal haematopoiesis, an age-related pre-cancerous condition also known as CHIP, which can progress to leukaemia. As lead researcher Dr Catriona Jamieson put it, “Space is the ultimate stress test for the human body.”
Mutations and Instability
The study also exposed a rise in DNA mutations and genomic instability in the stem cells, suggesting that even brief missions could affect long-term health. Past work, such as NASA’s Twins Study, had uncovered telomere shifts and genome changes in astronauts, findings now echoed at a cellular level.
Health Risks for Long-Duration Missions
As agencies plan for extended journeys, such as trips to Mars, the accelerated ageing of critical stem cells raises concerns about immune decline, cancer risk, and impaired recovery from injuries. The findings reinforce the need to integrate biological monitoring into missions and to explore protective strategies, including real-time diagnostics, shielding, and potential stem cell boosting therapies.
Emerging research initiatives, from UC San Francisco’s tissue-chip experiments to Stanford’s studies on muscle and cellular changes in microgravity, show that no corner of human biology is immune to extraterrestrial stress. The work, part of NASA’s Space Biology Programme and carried out at UC San Diego’s Moores Cancer Center, adds weight to calls for countermeasures as exploration shifts from low Earth orbit toward deep-space living.
The full findings are detailed in Cell Stem Cell.
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