Humans venturing into space can have negative effects on the body. Sending a manned mission to Mars requires more than a powerful launch
rocket. Preparation work also includes learning how a three-year space flight
could affect the human body.
With funding from the National Aeronautics
and Space Administration (NASA), researchers at the Wake Forest
Institute for Regenerative Medicine and colleagues are using human stem
cells to measure the effects of deep space radiation.
‘The radiation encountered in deep space travel may increase the risk of leukemia in humans.’
Using mice transplanted with human stem cells, the research team has
demonstrated for the first time that the radiation encountered in deep
space travel may increase the risk of leukemia in humans.
"Our results are troubling because they show radiation exposure
could potentially increase the risk of leukemia in two ways," said
Christopher Porada, associate professor of regenerative medicine
and senior researcher on the project.
As part of this ongoing project, the group has identified and is
currently testing a common dietary supplement for its ability to protect
astronauts from these damaging effects.
"It is rewarding to use our expertise in stem cells to help NASA
evaluate the potential health risks of space travel and hopefully
develop strategies to address them," said Porada.
Radiation exposure is believed to be one of the most dangerous
aspects of traveling to Mars, according to NASA. The average distance to
the red planet is 140 million miles, and a roundtrip could take three
The goal of the study, published in the journal Leukemia
was to assess the direct effects of simulated solar energetic particles
(SEP) and galactic cosmic ray (GCR) radiation on human hematopoietic
stem cells (HSCs). These stem cells comprise less than 0.1% of the bone
marrow of adults, but produce the many types of blood cells that
circulate through the body and work to transport oxygen, fight
infection, and eliminate any malignant cells that arise.
For the study, human HSCs from healthy donors of typical astronaut
age (30-55 years) were exposed to Mars mission-relevant doses of protons
and iron ions - the same types of radiation that astronauts would be
exposed to in deep space - at the NASA Space Radiation Laboratory at
Brookhaven National Laboratory. Researchers at the Wake Forest Institute
for Regenerative Medicine then performed laboratory and animal studies
to define the impact of the exposure.
These exposure levels that simulated deep space radiation were found
to dramatically affect the health and function of the HSCs. "Radiation
exposure at these levels was highly deleterious to HSC function,
reducing their ability to produce almost all types of blood cells, often
by 60-80%," said Porada. "This could translate into a severely
weakened immune system and anemia during prolonged missions in deep
Previous studies by other researchers had already demonstrated
that exposure to high doses of earthly radiation, such as from X-rays,
can have harmful (even life-threatening) effects on the body's ability
to make blood cells, and can significantly increase the likelihood of
cancers, especially leukemias. However, the current study was the first
to show a damaging effect of low, mission-relevant doses of space
The current study is significant because it shows that radiation
affected cells at the stem cell level. It caused mutations in genes
involved in the hematopoietic process, and it dramatically reduced the
ability of HSCs to give rise to mature blood cells.
The next step was to assess how the cells would function in the
body. Mice were transplanted with GCR-irradiated human HSCs, essentially
"humanizing" the animals. The mice developed what appears to be T-cell
acute lymphoblastic leukemia - the first demonstration that exposure to
space radiation may increase the risk of leukemia in humans.
"Our results show radiation exposure could potentially increase the
risk of leukemia in two ways," said Porada. "We found that genetic
damage to HSCs directly led to leukemia. Secondly, radiation also
altered the ability of HSCs to generate T and B cells, types of white
blood cells involved in fighting foreign 'invaders' like infections or
tumor cells. This may reduce the ability of the astronaut's immune
system to eliminate malignant cells that arise as a result of
Porada said the findings are particularly troubling given previous
work showing that conditions of weightlessness/microgravity present
during spaceflight can also cause marked alterations in astronaut's
immune function, even after short duration missions in low earth orbit,
where they are largely protected from cosmic radiation. Taken together,
the results indicate that the combined exposure to microgravity and
SEP/GCR radiation that would occur during extended deep space missions,
such as to Mars, could potentially exacerbate the risk of
immune-dysfunction and cancer.
NASA's Human Research Program explores not only the effects of
radiation, but also conditions of microgravity, isolation and
confinement, hostile and closed environments, and distance from earth.
The ultimate goal of the research is to make space missions as safe as