Spaceflight Accelerates Aging in Human Stem Cells, Study Reveals

Research has unveiled that exposure to spaceflight accelerates the aging process in human stem cells, a finding that could significantly impact future space exploration and astronaut health. The study, conducted during four resupply missions to the International Space Station (ISS) from late 2021 to early 2023, demonstrates how microgravity affects stem cell functionality. This research was partially funded by NASA and published on March 15, 2024, in the journal Cell Stem Cell.

Lead author Catriona Jamieson, director of the Sanford Stem Cell Institute and professor of medicine at the University of California, San Diego, emphasized that stem cells exhibit reduced functionality in space. “In space, stem cells decline in function,” Jamieson stated. “They actually reduce their ability to renew themselves or regenerate, which is crucial for long-term space missions.”

The investigation involved analyzing bone marrow stem cells from patients undergoing hip replacement surgery. These stem cells were placed on a sterile sponge matrix inside bioreactors designed to mimic their natural environment. Once aboard the ISS, an artificial intelligence system monitored the cells, observing that they remained active rather than entering a dormant state as they typically would on Earth.

Jamieson noted, “Our stem cells should be asleep 80 percent of the time to retain their full function.” In contrast, in the microgravity of space, the cells became functionally exhausted, raising concerns about their ability to support the immune system. Some of the stem cells were subjected to up to 45 days of spaceflight, becoming more active and showing signs of accelerated aging. This increased activity led to a depletion of their energy reserves and a diminished capacity to generate new cells.

The study revealed that under stress, these stem cells began to activate normally dormant segments of DNA, referred to as the “dark genome.” Jamieson explained, “Under conditions of strong stress, we activate these repetitive elements. They send the stem cells into a death spiral, causing them to age too quickly.” This phenomenon mirrors the stress seen in cells from patients with preleukemic disorders, which Jamieson actively studies in her work to prevent the progression to leukemia.

Looking ahead, Jamieson plans to conduct further research into potential countermeasures to mitigate the aging effects observed in stem cells during space missions. “We can use these bioreactors, or avatars for stem cell health, to predict who’s likely to do well and who’s likely to do extremely badly in space,” she explained, mentioning upcoming clinical trials for medications aimed at counteracting the impact of the dark genome.

Encouragingly, preliminary results from another study suggest that stem cells can recover from accelerated aging once astronauts return to Earth, although this recovery may take approximately a year. The implications of this research extend beyond space exploration; it may also enhance understanding of cancer-related stem cell stress, as the same damage mechanisms observed in space are present in cancer patients.

The findings highlight significant health risks for astronauts on extended missions, potentially compromising their blood and immune systems. Arun Sharma, a stem cell biologist and associate professor at Cedars-Sinai Medical Center in California, noted that these results could aid in developing therapies to slow or reverse aging processes.

Moreover, Luis Villa-Diaz, an assistant professor in biological sciences at Oakland University, stated that while this study offers compelling evidence of the potential damage caused by radiation exposure and microgravity, it also provides a roadmap for addressing these challenges and supporting future space exploration.

“Knowing the potential negative effects that low Earth orbit has on stem cell aging and function gives us directions to address these issues,” Villa-Diaz added.

The research reflects a growing body of work examining how spaceflight impacts biological systems, moving from earlier studies that suggested vulnerabilities to clearer evidence of aging. Elena Kozlova, a professor at the University of Uppsala in Sweden, noted the complexities of the findings, as her own research indicated that microgravity might promote a more youthful state in certain stem cell populations.

As space agencies prepare for longer missions, understanding the biological challenges posed by microgravity will be critical to ensuring astronaut health and safety. This study marks a significant step forward in addressing the implications of spaceflight on human biology, with potential benefits for both space explorers and medical research on Earth.