Cold Spring Harbor Laboratory (CSHL) scientists recently led a team of researchers to study potential effects of space radiation on astronauts. The results of their study are revealing and will provide the foundation for ensuring the safety of crew members participating in long distance space travel.
Measures to protect astronauts from health risks caused by space radiation will be important during extended missions to the moon or Mars, say researchers in a paper currently online in Experimental Neurology.
Using a mouse model designed to reveal even slight changes in brain cell populations, scientists found radiation appeared to target a type of stem cell in an area of the brain believed to be important for learning and mood control.
The findings — from a team of researchers from The Cold Spring Harbor Laboratory, Brookhaven National Laboratory, NASA's Kennedy Space Center and the McKnight Brain Institute of the University of Florida (UF) — suggest that identifying medications or physical shielding to protect astronauts from cosmic and solar radiation will be important for the success of human space missions beyond low Earth orbit.
“Our discovery does not present any adverse issues for the astronaut program because the ground-based dose and application of radiation we used were not comparable to that seen for existing space travel,” said Dennis A. Steindler, Ph.D., executive director of UF's McKnight Brain Institute and co-investigator in the study. “But the exceptional sensitivity of these neural stem cells suggests that we are going to have to rethink our understanding of stem cell susceptibility to radiation, including cosmic radiation encountered during space travel, as well as radiation doses that accompany different medical procedures.”
Stem cells are important because they have the remarkable ability to renew themselves and produce many different cell types.
In this study, Cold Spring Harbor Laboratory scientists developed mice that were genetically engineered with easily identifiable, florescent stem cells. The stem cells lose their florescence when they transform into neurons, which makes it easier to account for them. Scientists from the NASA Space Radiation Laboratory located at the Brookhaven National Laboratory in Upton, NY, then administered a single dose of radiation to the mice about equal to the amount astronauts would receive after a three-year space voyage to Mars.
A CSHL team of scientists led by neurobiologist Grigori Enikolopov, Ph.D., then examined the mice and unexpectedly found that a special type of stem cell is selectively killed in the hippocampus. The cell is described as quiescent — or quiet — because even though it is the wellspring that repopulates the brain with new cells, it exists in relative repose while its daughter cells divide and reproduce in great numbers.
“Our findings are surprising because it is assumed that dividing cells are the most vulnerable to radiation — that is why radiation is used in cancer therapy,” said Enikolopov, who served as co-investigator and corresponding author for the project. “These stem cells divide quite rarely and it was unexpected that they would be the most vulnerable to this type of radiation. But at least two thirds of these quiescent cells died. The challenge now is to find something to protect those cells.”