Environmental radiation on large Japanese field mice in Fukushima reduced colony forming potential in hematopoietic progenitor cells without inducing genomic instability

Purpose To study the environmental radiation effects of wild animals after the Fukushima Dai-ichi nuclear power plant accident, we assessed effects on hematopoietic progenitor cells (HPCs) in large Japanese field mice (Apodemus speciosus). Materials and methods A. speciosus were collected from three contaminated sites and control area. The air dose-rates at the control and contaminated areas were 0.96 +/- 0.05 mu Gy/d (Hirosaki), 14.4 +/- 2.4 mu Gy/d (Tanashio), 208.8 +/- 31.2 mu Gy/d (Ide), 470.4 +/- 93.6 mu Gy/d (Omaru), respectively. We investigated possible DNA damage and pro-inflammatory markers in the bone marrow (BM) cells. The colony-forming potential of BM cells was estimated by the number of HPC colony-forming cells. Radiation-induced genomic instability (RIGI) in HPCs was also analyzed by quantifying delayed DNA damage in CFU-GM clones. Results Although no significant differences in DNA damage and inflammation markers in BM cells from control and contaminated areas, the number of HPC colonies exhibited an inverse correlation with air dose-rate. With regard to RIGI, no significant differences in DNA damage of CFU-GM clones between the mice from the control and the three contaminated areas. Conclusions Our study suggests that low dose-rate radiation of more than 200 Gy/d reduced HPCs, possibly eliminating genomically unstable HPCs.