Sending a manned mission to Mars requires not only a powerful launch vehicle, but also an understanding of how a three-year space flight could affect the human body.
With funding from the National Aeronautics and Space Administration (NASA), scientists at the Wake Forest Institute for Regenerative Medicine and their colleagues used human stem cells to determine the effects of radiation exposure in deep space.
The research team has demonstrated for the first time that radiation from long-distance space flights can increase the risk of developing leukemia in humans.
“I hope our experience will help NASA assess potential risks and develop strategies to address them,” said Christopher Porada, senior scientist on the project. The group is currently testing a nutritional supplement that could protect astronauts from these devastating effects.
Radiation exposure is one of the most dangerous aspects of traveling to Mars, according to NASA. The average distance to the Red Planet is about 200 million kilometers, and the entire journey can take three years.
The aim of the study, published in the journal Leukemia, was to evaluate the direct effects of solar energy particles (SEP) and galactic cosmic rays (GCR) radiation on human hematopoietic stem cells (HSCs). These stem cells contain less than 0.1% bone marrow, but produce many types of blood cells that circulate throughout the body and are responsible for transporting oxygen, fighting infection, and eliminating any cancerous cells.
For the study, stem cells were taken from healthy donors aged astronauts (30–55 years). During the experiment, they were exposed to protons and iron ions in doses characteristic of deep space. Then laboratory and experimental studies were carried out to determine the effects of radiation.
“We found that radiation reduced the ability of HSCs to produce almost all types of blood cells by 60–80%,” Porada said. "This can lead to severe weakening of the immune system and anemia during extended missions in deep space."
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In the next step, the scientists evaluated how the cells would function in the body. Irradiated human HSC cells were transplanted into mice, effectively "humanizing" the animals. As a result, they developed acute lymphoblastic leukemia.
"Irradiation can increase the risk of developing leukemia," concluded Porada. "In addition, radiation affected the ability of HSCs to generate types of white blood cells involved in fighting foreign invaders such as infections or tumor cells. This could reduce the immune system's ability to eliminate malignant cells resulting from radiation-induced mutations."
The results are particularly disturbing given previous work showing that microgravity conditions can also induce noticeable changes in the immune system, even after short missions in low Earth orbit, where astronauts are largely shielded from radiation, Porada said. The combined effects of microgravity and radiation can exacerbate the risk of immune dysfunction and cancer.
NASA's Human Research Program is designed to make space missions as safe as possible. It explores not only the effects of radiation, but also microgravity conditions, isolation and confinement in confined environments far from Earth.