Simulated cosmic radiation caused long-term heart fibrosis in rats
Researchers observed cardiac collagen accumulation and persistent immune alterations in rats exposed to simulated spaceflight stressors.
A study published in PLoS ONE revealed that simulated galactic cosmic radiation and simulated microgravity induce persistent pathological changes in male rats 
doi.orgPLoS ONEdoi.orgOpen source ↗. Investigators from the Medical College of Wisconsin subjected male WAG/RijCmcr rats, aged 8–9 months, to hind limb unloading for 30 days and whole-body exposure to a simplified cosmic radiation spectrum at a rapid dose of 1.5 Gy. A separate follow-on experiment tested a Mars-relevant radiation dose of 0.75 Gy without unloading.
Perivascular fibrosis and genomic changes
Radiation exposure at 1.5 Gy increased perivascular collagen content in the heart after 270 days regardless of whether the animals underwent hind limb unloading doi.orgPLoS ONEdoi.orgOpen source ↗. The extent of fibrosis was indistinguishable between irradiated groups, demonstrating no interaction between the two stressors for this endpoint. At the lower dose of 0.75 Gy, cardiac perivascular fibrosis appeared after an extended follow-up period of 360 days. In addition, sequencing identified mutations, frameshifts, and deletions in genes associated with human disease within circulating nucleated blood cells from irradiated subjects.
Immune shifts under simulated microgravity
Hind limb unloading alone altered immune parameters, reducing concentrations of circulating cytokines and depleting splenic CD56+ cells doi.orgPLoS ONEdoi.orgOpen source ↗. Unloading combined with sham irradiation led to elevated blood lymphocytes without affecting myeloid cells, an effect inhibited by concurrent radiation exposure. Neither radiation nor unloading, separately or combined, disrupted calcium homeostasis.
