A new study funded by NASA has found that spaceflight accelerates the aging of blood-forming stem cells in the human body, raising potential concerns about the long-term health effects of extended missions in space. The research, published in the journal Cell Stem Cell, monitored human hematopoietic stem and progenitor cells flown aboard four SpaceX resupply missions to the International Space Station (ISS) and compared them to identical samples kept on Earth.
The experiments were conducted using cells collected from multiple human donors. These cells, which are responsible for producing all types of blood and immune cells in the bone marrow, were flown to the ISS on missions launched in December 2021, July 2022, November 2022, and March 2023. The samples remained in orbit for 30 to 45 days before being returned for analysis. Researchers found that space-exposed stem cells exhibited a measurable decline in their ability to regenerate. The cells became overactive during the flight period, losing their capacity to return to a resting state that is essential for long-term maintenance and recovery.
This over-activation depleted the cells’ regenerative reserves, diminishing their function. The analysis also showed elevated levels of DNA damage, telomere shortening at the ends of chromosomes, and signs of cellular stress and inflammation. In addition to functional decline, the cells showed increased mitochondrial activity and triggered expression of normally inactive parts of the genome, sometimes referred to as the “dark genome.” These changes, scientists said, are characteristic of aging and were not observed in the control samples kept on Earth.
Scientists identify aging markers in blood-forming cells
The study noted that the response varied between individual donors, indicating possible differences in biological resilience to spaceflight. The principal investigator of the study, Dr. Catriona Jamieson, Director of the Sanford Stem Cell Institute at the University of California San Diego School of Medicine, said the findings offer new insight into how space conditions affect the human body at a cellular level. She emphasized that the differences observed between donor cells suggest a degree of individual variation in how stem cells respond to environmental stressors such as microgravity and space radiation.
The research involved the use of artificial intelligence-guided nano-bioreactor systems that enabled scientists to monitor cellular changes in real time while in orbit. The stem cells were housed in compact, self-contained units aboard the space station that allowed continuous monitoring of their growth, gene expression, and metabolic activity. These systems provided a level of biological detail not previously possible in microgravity experiments.
Human cells lose regenerative function in microgravity
Unlike Earth, where the atmosphere and magnetic field offer substantial protection from cosmic radiation, astronauts in low Earth orbit are exposed to higher levels of ionizing radiation. Combined with microgravity, this environment presents unique challenges to human physiology. Previous studies have linked spaceflight to bone density loss, muscle atrophy, cardiovascular strain, and immune system changes. The current findings add stem cell aging and dysfunction to that list.
The study was part of NASA’s ongoing efforts to understand how spaceflight impacts human biology in preparation for longer-duration missions beyond low Earth orbit. While the study did not draw conclusions about long-term health risks, it provided empirical data on cellular responses under spaceflight conditions. Further research is continuing, including additional experiments launched aboard a SpaceX resupply mission in August 2025. The results contribute to a growing body of scientific literature examining how the space environment affects the human body at a fundamental level. – By Content Syndication Services.