The small intestine is particularly vulnerable to space radiation, raising further concern over human deep-space travel.
Everybody wants to go to
space.
But before we can go deeper -- and settle on planets such as
Mars -- we need a better understanding of cosmic pathologies and how they may arise.
Researchers at Georgetown University Medical Center (GUMC) in Washington, DC have been studying how ionizing radiation may affect the gastrointestinal (GI) tract in humans to better prepare astronauts to make long-duration trips across the solar system.
On such missions, astronauts will be exposed to radiation from a number of different sources and, currently, there are no effective methods of blocking that radiation out.
"With the current shielding technology, it is difficult to protect astronauts from the adverse effects of heavy ion radiation. Although there may be a way to use medicines to counter these effects, no such agent has been developed yet," stated Kamal Datta, project leader and senior investigator on the study, in a press release Monday.
The GI tract is a great candidate for experimentation because the effects of ionizing radiation on the biological processes are already well-known. Over the course of three to five days, the cells in the tract are renewed -- new cells divide and replace old cells. Disturbance of this process results in a raft of changes -- some that even lead to the formation of tumors.
At the
NASA Space Radiation Laboratory (NSRL) in New York, scientists subjected mice to low doses of heavy ion radiation or gamma rays. By comparing the mice with those that were not exposed to any radiation, the scientists were able to determine how the gastrointestinal tract may be affected by the dangers of space. After seven days, 60 days or 12 months post-exposure, mice were euthanized and assessed.
Their results demonstrated that gamma rays only produced small, modest effects on the cells of the small intestine that were able to recover to normal within 60 days. However, heavy ion irradiation caused a panoply of changes to those cells, with decreased migration and increased cell proliferation with ongoing DNA damage that persisted even a year after exposure.
In a second subset of mice, euthanized 150 days after a dose of heavy ion radiation, the research team showed that those alterations in the small intestine had the potential to increase the likelihood of developing tumours.
The poor, helpful mice.
"While short trips, like the times astronauts traveled to the Moon, may not expose them to this level of damage, the real concern is lasting injury from a long trip, such as a Mars or other deep space missions which would be much longer," explained Datta.
A key in prolonging our time in space will be to better understand the changes that occur to human physiology -- and how we may counteract any pathologies that may arise. Further studies will look to address how the precursors to these cells are affected by radiation and hopefully keep us on track for safe deep-space travel in the next decade.