EFFECTS OF IRRADIATION OF CBA CA MICE ON HEMATOPOIETIC STEM-CELLS ANDSTROMAL CELLS IN LONG-TERM BONE-MARROW CULTURES

Following 200 cGy total body irradiation, 20-25% of CBA/Ca mice and th eir CBA/B and CBA/H sublines develop myeloid leukemia, To determine wh ether hematologic changes in vitro were detectable, long-term marrow c ultures (LTBMCs) were established from the right and left hind limbs o f 11 individual control and 11 CBA/B mice 100-114 days after 200 cGy t otal body irradiation. Individual cultures were studied weekly for cum ulative production of nonadherent cells and colony-forming, hematopoie tic progenitor cells. Control cultures produced significantly more non adherent cells over 25 weeks in long-term marrow culture compared to t hose from irradiated (treated) mice. Permanent stromal cell lines were established from control and irradiated CBA/B mouse LTBMCs and clonal sublines were established. The stromal cell lines from LTBMCs of in v ivo irradiated CBA/B mice had uniformly lower plating efficiencies, an d only one formed a permanent clonal subline at 100-fold lower frequen cy compared to stromal cell lines from control mouse LTBMCs. The irrad iation sensitivity of both uncloned and clonal sublines was similar by single-hit, multihit or by linear quadratic formula, Cocultivation of an IL-3-dependent hematopoietic progenitor cell line established from a control CBA/B, LTBMC with control or irradiated stromal cell lines derived from either a control (CC3) or the one successfully cloned in vivo irradiated (CT4) LTBMC, produced few cobblestone islands in the p resence of IL-3. In contrast, formation of cobblestone islands in the presence of L cell-conditioned medium as a source of M-CSF was signifi cantly greater, and these persisted for 21 days on both CC3 and CT4 st romal lines. The data provide evidence for irradiation induced changes in the bone marrow stromal cell compartment of CBA/B mice which persi st and are detectable in vitro 6 months after explant of the cells to culture. These marrow stromal cell lines may provide valuable resource s for analyzing the molecular biologic changes in the hematopoietic mi croenvironment during irradiation leukemogenesis.