Spaceflight Accelerates Aging in Human Stem Cells, Study Reveals

New research indicates that exposure to spaceflight significantly accelerates the aging process in human stem cells. A study funded in part by NASA reveals that certain stem cells experience a decline in functionality while in microgravity. This research enhances the understanding of how space exploration affects the human body, particularly for long-term missions.

The study, published on March 15, 2024, in the journal Cell Stem Cell, was conducted during four resupply missions to the International Space Station (ISS) operated by SpaceX between late 2021 and early 2023. According to lead study author Catriona Jamieson, director of the Sanford Stem Cell Institute and professor of medicine at the University of California, San Diego, the research found that stem cells in space not only age faster but also lose their ability to regenerate effectively.

“In space, stem cells decline in function,” Jamieson stated. “They actually reduce their ability to renew themselves or regenerate, and that’s an important thing to be able to know for long-term space missions.”

The implications of this research extend beyond space exploration. It suggests that astronauts may face significant health risks due to weakened blood and immune systems during prolonged missions. This concern is underscored by a previous NASA experiment conducted in 2010 that explored the effects of microgravity on embryonic stem cells from mice.

In the current study, researchers focused on bone marrow stem cells provided by patients who underwent hip replacement surgery. These cells, essential for immune system health, were placed on a sterile sponge matrix within bioreactors designed for space conditions. While aboard the ISS, an artificial intelligence system monitored the cells in real-time to assess their condition.

Jamieson noted that under normal circumstances, stem cells should remain inactive for about 80 percent of the time to maintain optimal function. Unfortunately, in the microgravity environment of space, the cells became overactive and could not return to their dormant state. “The stem cells woke up, and they didn’t go back to sleep, and they became functionally exhausted,” she explained.

Some of the stem cells remained in space for as long as 45 days, during which they showed signs of accelerated aging. This increased activity led to the depletion of their energy reserves and a reduction in their capacity to generate new cells. In a surprising revelation, the study also found that stress from microgravity activated dormant sections of DNA, referred to as the “dark genome.”

“Under conditions of stress, really strong stress, we activate these repetitive elements,” Jamieson said, highlighting that these fragments, remnants of ancient retroviruses, could contribute to cellular decline. “They send the stem cells into a death spiral. The cells just feel overstressed.”

The research parallels observations made by Jamieson in patients with preleukemic disorders, where similar stress-induced cellular changes occur. With nine space missions under her belt, Jamieson is looking ahead to future studies aimed at developing countermeasures against the aging process 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 stated. Upcoming clinical trials may investigate potential medications to mitigate the effects of the dark genome activity.

Encouragingly, preliminary findings from an upcoming study suggest that stem cells can recover from accelerated aging once astronauts return to Earth, although this recovery may take about a year.

The implications of this research reach beyond the realm of space travel. It may also benefit cancer patients, whose stem cells exhibit similar stress-related damage. “I think this is an important tool for us to accelerate the pace of cancer research,” Jamieson added.

For researchers like Arun Sharma, a stem cell biologist at Cedars-Sinai Medical Center in California, these findings underscore the potential health risks associated with long-duration space missions. Sharma, who was not involved in the study, acknowledged that the research could provide valuable insights into aging processes and lead to new therapeutic developments.

The study also highlights the damaging effects of radiation exposure and microgravity on stem cells, emphasizing the need for strategies to mitigate these risks. Luis Villa-Diaz, an assistant professor in biological sciences at Oakland University in Michigan, stated, “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.”

Research on stem cells in space has yielded mixed findings, with some studies suggesting that spaceflight may even promote youthful characteristics in certain stem cell populations. Elena Kozlova, a professor at Uppsala University in Sweden, noted that not all studies align in their conclusions, indicating the complexity of stem cell behavior in microgravity.

As space exploration continues to advance, understanding the impact of microgravity on human health remains crucial. The findings from this study may not only inform the future of long-term space missions but also contribute to biomedical advancements that benefit individuals on Earth.