Effects of radiation on human hemopoietic stem cells

The purposes of the present study were to investigate : 1) effects of oxygen tension, serum concentration, and growth factors on human bone marrow fibroblast colony (CFU-F) formation ; 2) effects of Co-60, Cf-252, and tritiated water beta rays (HTO) on hemopoietic stem cells from fresh bone marrow cells ; and 3) the number of hemopoietic stem cells and chromosome aberrations in A-bomb survivors exposed at short distance. Relative plating efficienty (PE) and relative size of CFU-F colony were significantly increased at lower oxygen tensions. CFU-F colony formation was dependent on the concentration of fetal calf serum (FCS), irrespective of oxygen tension. There was a positive correlation between PE and FCS concentration. CFU-F colony formation was suppressed by the following growth factors : phorbol myristate acetate (50 ng/ml or more), cholera toxin (10-8 to 10-11 M), and fibroblast growth factor (50 - 200 ng/ml). The D0 values of Co-60, Cf-252, and HTO were 0.84 +- 0.03 Gy, 0.31 +- 0.01 Gy, 0.29 +- 0.01 Gy, respectively, for CFU-E ; 0.88 +- 0.07 Gy, 0.50 +- 0.08 Gy, and 0.68 +- 0.06 Gy for BFU-E ; and 1.24 +- 0.30 Gy, 0.60 +- 0.10 Gy, and 0.92 +- 0.06 Gy for HTO. Survival curves were linear, except for those of CFU-F for Co-60 and Cf-252. Using RBE of Co-60 as the standard, RBE of Cf-252 and HTO were 2.7 and 2.9, respectively, for CFU-E ; 1.8 and 1.3 for BFU-E ; and RBE of Co-60 and HTO for CFU-F depended on radiation doses (3 or more for one Gy or less). In A-bomb survivors, a significant decrease was observed in the number of granulopoietic stem cells and stromal progenitor. Stable type chromosome aberration was observed in all cases. (Namekawa, K.)