Radiation and Simulated Microgravity Double Heart Vessel Collagen in Rat Study
Male rats exposed to simulated cosmic radiation develop roughly twice as much collagen around heart blood vessels at long-term follow-up, raising new questions for long-duration space exploration. The study, published in PLOS ONE and conducted by researchers associated with the Medical College of Wisconsin, examined biological changes months after exposure. While simulated weightlessness altered immune signaling, combining both spaceflight stressors did not consistently worsen cardiac fibrosis.
Simulating Space Environment in Laboratory Experiments
At NASA’s Space Radiation Laboratory at Brookhaven National Laboratory, investigators used five ion types delivered through six beams to approximate galactic cosmic radiation components after spacecraft shielding. Rats received radiation doses of 0.75 gray or 1.5 gray, with the lower dose treated as representative of a three-year Mars mission. To simulate microgravity, some animals underwent 30 days of hindlimb unloading, a technique that suspends the rear legs to alter fluid distribution and loading without removing gravity entirely.
Long-Term Scarring Around Coronary Blood Vessels
At 360 days after exposure, rats receiving 0.75 gray without hindlimb unloading showed approximately double the collagen deposition around cardiac vessels, known as perivascular cardiac fibrosis. Animals receiving 1.5 gray showed a similar increase at 270 days. The study did not measure cardiac pumping performance.
Immune System Signaling and Genomic Changes
Immune and genomic measurements revealed complex patterns that challenged simple cumulative assumptions. Hindlimb unloading alone reduced concentrations of 20 out of 27 examined cytokines while increasing circulating immune-cell populations, mirroring six decreased cytokines shared with findings from the NASA Twins Study. However, adding the higher radiation dose prevented those cytokine reductions. Genomic analysis of blood-cell DNA from a small subset of six rats identified variants in 30 genes associated with clonal hematopoiesis, though individual animal differences dominated the results.
Frequently Asked Questions About Deep Space Health Risks
Did the experiments prove that astronauts will develop heart disease on Mars?
No, the findings are based on a specific rat model evaluated under ground-based simulations and do not quantify the exact likelihood of heart attacks or cancer in humans traveling to Mars.
How did researchers simulate microgravity on Earth?
Scientists used hindlimb unloading, a harness method that elevates a rat’s hindquarters to reduce weight-bearing on the lower body and alter fluid distribution, though it does not fully replicate actual spaceflight conditions.
What limitation exists regarding radiation delivery in the study?
The study used a simplified simulator that cannot reproduce the entire radiation environment of deep space, and compressed radiation delivery limits direct human predictions.