Analysis of cell cycle in mouse bone marrow cells following acute in vivo exposure to 56Fe ions

A pilot study was conducted to examine the magnitude of cell-cycle delay and apoptosis in bone marrow (BM) cells collected at 18, 42 and 66 hr from radiosensitive CBA/CaJ mice and radioresistant C57BL/6J mice following a whole-body in vivo exposure to 1 GeV/amu 56Fe ions or 137Cs γ rays. At each sacrifice, BM cells were collected from three mice of each strain per dose of 56Fe ions (0, 10 and 100 cGy) and two mice of each strain per dose of 137Cs γ rays (0, 100 and 300 cGy). A significant G1-arrest (ANOVA, p<0.05) was observed at 18 hr after exposure of mice to 100 cGy of 56Fe ions or 300 cGy of 137Cs γ rays, relative to their corresponding sham-controls, resulting in a significant decrease in the percentage of cells cycling into S-phase in both strains. The percentage of S-phase cells subsequently increased and persisted up to 66 hr post-irradiation. Significant numbers of G2/M cells were found at 18 and 66 (but not at 42) hr post-irradiation, regardless of radiation-type or mouse-strain. It is likely that BM cells have undergone at least one cell cycle at 66 hr after exposure of mice to either 100 cGy 56Fe ions or 300 cGy 137Cs γ rays. Our study is the first to investigate the in vivo effects of 56Fe ions (1 GeV/amu) on the cell cycle of mouse BM cells using flow cytometry. The cell-cycle distribution (but not the number of apoptotic cells) was dependent on radiation-dose and harvest-time. (author)