Study Reveals Spaceflight Accelerates Aging in Human Stem Cells

Research has uncovered that spaceflight accelerates the aging process in human stem cells, a finding that could significantly impact our understanding of human health during long-term space missions. Conducted by a team led by Catriona Jamieson, director of the Sanford Stem Cell Institute and a professor at the University of California, San Diego, the study highlights how microgravity affects stem cell function in real-time aboard the International Space Station.

The study, partially funded by NASA, monitored human bone marrow stem cells during four resupply missions operated by SpaceX from late 2021 to early 2023. Published on March 15, 2024, in the journal Cell Stem Cell, the research illustrates the decline in stem cell functionality in space, raising concerns for astronauts on extended missions.

In her analysis, Jamieson emphasized that stem cells typically should remain inactive for about 80 percent of their lifecycle to maintain their regenerative capacity. Yet, conditions in space disrupt this balance. “The stem cells woke up, and they didn’t go back to sleep, and they became functionally exhausted,” she noted. Such exhaustion compromises their ability to support a healthy immune system, which is crucial for astronauts exposed to the stresses of space travel.

The research involved stem cells collected from patients undergoing hip replacement surgery. These cells were housed in specially designed bioreactors onboard the ISS, where they were continuously monitored by an artificial intelligence system. The results revealed that some stem cells endured up to 45 days in space, but their increased activity led to significant energy depletion and signs of accelerated aging.

According to Jamieson, these stem cells began activating previously dormant regions of DNA known as the “dark genome,” which consists of ancient retroviruses. “Under conditions of stress, really strong stress, we activate these repetitive elements,” she explained. “They send the stem cells into a death spiral.” This phenomenon echoes the stress observed in stem cells of patients with preleukemic disorders, a condition Jamieson actively researches in her medical practice.

Looking forward, Jamieson plans to investigate potential countermeasures that could mitigate the accelerated aging process observed in stem cells. “We can actually 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 said. The findings could inform clinical trials aimed at developing medications to counteract the detrimental effects of stress on stem cells.

Preliminary results from additional studies indicate that stem cells may recover from accelerated aging after astronauts return to Earth, though this recovery process may take approximately one year. This aspect of the research could also benefit cancer patients, as their stem cells exhibit similar stress-related damage.

The implications of this study extend beyond space exploration. According to Arun Sharma, a stem cell biologist at Cedars-Sinai Medical Center, the findings suggest that long missions could weaken astronauts’ blood and immune systems, thereby raising health risks. He stated that understanding these effects may lead to new therapies aimed at slowing or reversing the aging process.

Researchers such as Luis Villa-Diaz from Oakland University support these findings, highlighting the strong evidence that radiation exposure and microgravity can adversely affect stem cells. “The good news is that knowing the potential negative effects that low Earth orbit has on stem cell aging and function gives us directions to address these issues and develop strategies to prevent or counteract these effects,” he remarked.

While earlier studies hinted at vulnerabilities in stem cells due to space conditions, this research provides clearer evidence of the aging process in response to spaceflight. Elena Kozlova from Uppsala University also noted that not all studies align in their findings, with some indicating that spaceflight may promote growth in certain stem cell populations.

Overall, the research underscores the necessity of understanding stem cell dynamics in space to ensure the health and safety of astronauts during future exploration missions.