Study Reveals Spaceflight Accelerates Aging in Human Stem Cells

Research has unveiled that spaceflight accelerates aging in human stem cells, highlighting the significant impacts of space exploration on human health. A study published in Cell Stem Cell on March 14, 2024, indicates that stem cells, essential for tissue maintenance and repair, lose functionality in microgravity environments.

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

The research, partially funded by NASA, was conducted during four resupply missions to the International Space Station by SpaceX from late 2021 to early 2023. This study is notable for being the first to observe stem cell behavior in low Earth orbit in real-time, providing insights into the health management of astronauts.

Monitoring stem cells in space
The investigation focused on bone marrow stem cells from patients undergoing hip replacement surgery. These stem cells, vital for immune and blood health, were placed in sterile bioreactors resembling cell phones. Onboard the International Space Station, an artificial intelligence system continuously monitored the cells.

Jamieson explained that under normal conditions, stem cells should remain inactive 80 percent of the time to retain full functionality. “However, in space, microgravity and cosmic radiation influenced their well-being,” she noted. The stem cells became overly active, leading to functional exhaustion.

Some cells experienced up to 45 days of spaceflight and showed signs of accelerated aging. They activated normally dormant sections of DNA, referred to as the “dark genome,” which are retroviral remnants that constitute approximately 55 percent of human DNA. “Under conditions of stress, we activate these repetitive elements,” Jamieson said, adding that this could push stem cells into a “death spiral.”

Potential implications for cancer treatment
Jamieson, who has participated in nine space missions, plans to conduct further studies to explore countermeasures against the aging process observed in space. She highlighted the potential of using bioreactors to predict which astronauts may cope well in space and which may struggle, suggesting upcoming clinical trials for medications to mitigate the effects of dark genome activity.

Encouragingly, preliminary results from a separate study indicate that stem cells can recover from accelerated aging after astronauts return to Earth, though recovery may take about a year. This research could also provide valuable insights for cancer patients, as their stem cells exhibit similar stress-related damage.

Health risks for astronauts
The findings raise concerns about the health of astronauts during long missions. Arun Sharma, a stem cell biologist and associate professor at Cedars-Sinai Medical Center, noted that weakened blood and immune systems could increase health risks for those in space. He agreed with Jamieson that the study’s results could enhance understanding of the aging process and lead to new therapies.

According to Luis Villa-Diaz, an assistant professor at Oakland University, the research underscores the potential damage microgravity and radiation exposure can inflict on stem cells, emphasizing the health risks associated with extended space travel. “Knowing the potential negative effects that low Earth orbit has on stem cell aging gives us directions to address these issues,” he stated.

Contrasting findings from other studies suggest not all research on stem cells in space points in the same direction. Elena Kozlova, a professor at the University of Uppsala, observed in her work that certain conditions in space might promote a more youthful state in some stem cell populations.

As space exploration continues to advance, understanding the effects of microgravity on human biology will be crucial. The findings from this study not only contribute to astronaut health but may also translate into significant biomedical advancements for patients on Earth.