Sending a manned mission to Mars needs more than simply building a powerful launch rocket. Scientist are also studying how a three-year space flight would affect the human body.
Researchers at the Wake Forest Institute for Regenerative Medicine have been funded by the National Aeronautics and Space Administration (NASA). They are using human stem cells to measure the effects of deep space radiation by using mice transplanted with human stem cells.
The team has shown for the first time that the radiation present in deep space travel may increase the risk of leukemia in humans.
Christopher Porada, Ph.D., associate professor of regenerative medicine and senior researcher on the project is troubled by the results, as these show that radiation exposure could potentially increase the risk of leukemia in two ways.
The team has identified, and is currently testing, a common dietary supplement as part of this ongoing project. They are hoping the supplement will be able protect astronauts from the damaging effects of radiation.
Porada finds it rewarding to use their expertise in stem cells to help NASA evaluate the potential health risks of space travel. He hopes they will be able to develop strategies to mitigate the risks.
It is believed that radiation exposure is one of the most dangerous aspects of traveling to Mars. The distance to the red planet is 140 million miles, and a return trip could take three years.
The study was published in the journal Leukemia, and its aim was to assess the direct effects of simulated galactic cosmic ray (GCR) and solar energetic particles (SEP) radiation on human hematopoietic stem cells (HSCs). These stem cells produce the many types of blood cells that circulate through the body, although they comprise less than 0.1% of the bone marrow of adults. The blood cells produced fight infection, transport oxygen and eliminate any malignant cells that arise.
The study was conducted at the NASA Space Radiation Laboratory at Brookhaven National Laboratory. Human HSCs from healthy donors of typical astronaut age (30 to 55 years) were exposed to doses of protons and iron ions that were Mars mission relevant. In deep space, astronauts would be exposed to these types of radiation. Laboratory and animal studies to define the impact of the exposure were then performed by researchers at the Wake Forest Institute for Regenerative Medicine.
The exposure levels simulating deep space radiation were found to affect the function and health of the HSCs dramatically. According to Porada, radiation exposure at these levels was highly poisonous to HSC function and reduced their ability to produce almost all types of blood cells, often by as much as between 60 and 80 percent.
This could result in anemia and a severely weakened immune system during extended missions in deep space. It has already been shown in previous studies by other researchers that exposure to high doses of earthly radiation, such as from X-rays, can have harmful effects on the body’s ability to make blood cells. These effects can even be life threatening and can increase the likelihood of cancers, especially leukemia, significantly. The current study was the first to demonstrate the damaging effect of low, mission relevant doses of space radiation.
The current study is noteworthy because it shows that radiation affected cells at the stem cell level, and this dramatically reduces the ability of HSCs to produce mature blood cells. It also caused mutations in genes involved in the hematopoietic process.
The next step the researchers took was to determine how the cells would function in the body. Mice were transplanted with GCR-irradiated human HSCs. The mice developed what appears to be T-cell acute lymphoblastic leukemia. This is the first indication that exposure to space radiation may increase the risk of leukemia in humans.
Porada explained that these results show that radiation exposure could potentially increase the risk of leukemia in two ways. Radiation altered the ability of HSCs to generate B and T cells, the types of white blood cells involved in fighting foreign intruders like tumor cells or infections. Radiation also caused genetic damage to HSCs that led directly to leukemia. This may reduce the capacity of the astronaut’s immune system to eradicate malignant cells that arise because of mutations induced by radiation.
Porada found the results particularly troubling given that previous work showed that conditions of weightlessness and microgravity during spaceflight could also cause significant alterations in the astronaut’s immune function. This could occur even during short duration missions in low earth orbit where they are largely shielded from cosmic radiation. When combined, the results suggest that the combined exposure to microgravity and SEP/GCR radiation that would occur during an extended deep space mission to Mars could potentially aggravate the risk of cancer and immune dysfunction.
NASA’s Human Research Program is exploring the conditions of microgravity, effects of radiation, isolation and confinement, hostile and closed environments and distance from earth. The ultimate aim of the research is to make space missions as safe as humanly possible.