The effect of stem cell factor on irradiated human bone marrow

This study evaluates the effect of recombinant human stem cell factor (SCF) on the in vitro response of human bone marrow progenitor cells to irradiation. Light density nonadherent mononuclear cells were isolated from human bone marrow and resuspended in either semisolid culture or liquid culture with or without 100 ng/ml SCF. After 24 h in culture, cells were irradiated and assessed for survival of erythroid burst-forming unit, granulocyte colony-forming unit(s), or granulocyte-macrophage colony-forming unit precursors in the presence of erythropoietin, granulocyte colony-stimulating factor, or granulocyte-macrophage colony-stimulating factor, respectively. Incubation with SCF prior to irradiation (0–300 cGy) resulted in an increase in both absolute colony number and surviving fraction for erythroid burst-forming units, granulocyte colony-forming units, and granulocyte-macrophage colony-forming unit as compared to cultures that did not contain SCF. The mean surviving fraction enhancement ratio after 100 cGy ranged from 1.2 to 3.7. An increased fraction of CD34+ progenitors in S-phase after exposure to SCF may explain in part the apparent radioprotective effect of SCF on human bone marrow progenitor cells.