Spaceflight may cause blood stem cells to age faster

Human blood stem cells appear to age faster in space, a new study has found.

After spending 32-45 days in space, the stem cells showed several symptoms of ageing, including activation of normally silent DNA, replication errors, and increased mitochondrial stress. They also demonstrated increased activity, consuming more energy, resulting in impaired ability to regenerate and replicate.

'Space is the ultimate stress test for the human body. These findings are critically important because they show that the stressors of space – like microgravity and cosmic galactic radiation – can accelerate the molecular ageing of blood stem cells,' said Professor Catriona Jamieson from the University of California San Diego School of Medicine, who led the study published in Cell Stem Cell.

Professor Jamieson's team, in collaboration with Space Tango and NASA, collected hematopoietic stem and progenitor cells (HSPCs) donated by patients undergoing hip replacement surgery. HSPCs are found in human bone marrow, and they can form either platelets, white blood cells, or red blood cells.

The stem cell samples were divided between two nanobioreactors, allowing the cells to be monitored in real time. One of each pair was launched on one of four missions to the International Space Station, the other was kept on Earth as a control.

The space-flown cells showed differences from the controls. Unlike the control stem cells, which spent on average around 80 percent of their time inactive, the space-based cells demonstrated increased activity and higher mitochondrial stress.

Genetic analysis revealed other signs of stress, including shorter telomeres (protective caps on the ends of the chromosomes), increased DNA replication errors, and activation of the 'dark genome': sections of highly repetitive DNA associated with impaired cell function.

The paper builds on previous research, such as NASA's 2019 twin study, where astronaut Scott Kelly showed increased cellular ageing compared to his twin brother Mark, who remained on Earth. Notably, most of these observations were reversed when Scott returned to Earth; however, some took up to a year to return to normal, while others persisted (see BioNews 942).

It is thought that both microgravity, causing muscular atrophy and decreased bone density in astronauts, as well as increased exposure to cosmic radiation, which is usually filtered out by the Earth's atmosphere, can lead to increased genetic damage.

By understanding the accelerated ageing of stem cells in space, researchers can develop better techniques to monitor these biomarkers and develop therapies to protect astronauts' health.

'Knowing the potential negative effects that low Earth orbit has on [stem cell] ageing and function gives us directions to address these issues and develop strategies to prevent or counteract these effects, and support future space exploration,' Dr Luis Villa-Diaz from the biological sciences and bioengineering departments at Oakland University, Michigan, who was not involved in the study told CNN.

Beyond space travel, many of these increased ageing cellular pathways are seen in cancer and other diseases, so the research could help understand these too.