Radiosensitivity of cloned permanent murine bone marrow stromal cell lines: nonuniform effect of low dose rate.

The x-irradiation biology of supportive stromal cells of the bone marrow microenvironment was investigated by using cloned permanent cell lines that were established from hematopoietically active murine long-term bone marrow cultures. X-irradiation survival curves were derived for each cell line at either 120 cGy/min or clinical low dose rate (LDR) (5 cGy/min) that is used in total body irradiation protocols prior to bone marrow transplantation. Four cell lines, MBA-1, MBA-13, 14F2.1, and D2XRII (Group I) demonstrated a significant increase in D0 at 5 cGy/min (280 cGy, 270 cGy, 210 cGy, and 240 cGy, respectively) compared to 120 cGy/min (215 cGy, 210 cGy, 157 cGy, and 210 cGy, respectively) (p less than 0.05). In contrast, three other clonal cell lines, +/+ #2 cl 4, S1d #3, and GPI alpha-1 (Group II) showed no significant dose rate dependent change in D0 at 5 cGy/min (164 cGy, 174 cGy, and 159 cGy, respectively) compared to 120 cGy/min (159 cGy, 167 cGy, and 143 cGy, respectively). Group I and II cell lines could not be distinguished by differences in synthesis of extracellular matrix proteins including laminin, collagen types I and IV, or histochemically detectable enzymes. Three Group I lines (MBA-1, MBA-13, and D2XRII) and one Group II line, Sld #3, showed decreased support capacity for cocultivated hematopoietic stem cells in vitro. All seven lines had detectable polyA+ mRNA for monocyte colony-stimulating factor (M-CSF) as detected by molecular hybridization; one had detectable levels of polyA+ mRNA for granulocyte-macrophage colony-stimulating factor (GM-CSF) (D2XRII); one, detectable levels of polyA+ mRNA for interleukin 1 (IL-1); and none of the seven had detectable polyA+ mRNA for granulocyte colony-stimulating factor (G-CSF) or IL-3 (multi-CSF). The data indicate that some cells of the hematopoietic microenvironment may not be selectively protected by clinical low dose rate irradiation.(ABSTRACT TRUNCATED AT 250 WORDS)