Recovery of hemopoietic stromal progenitor cells after lethal total-body irradiation and bone marrow transplantation in mice.

The recovery of fibroblastic colony-forming units (CFU-F) in murine bone marrow hemopoietic stroma was studied during eighteen months after 9 Gy lethal total-body irradiation and reconstitution with syngeneic bone marrow cells. After an initial depletion, CFU-F numbers increased from 10% of normal values at three months to 40% at 18 months after treatment, irrespective of graft size and presence of CFU-F in the graft. Fourteen months after treatment 35% of all CFU-F present in the recipients' bone marrow was donor-derived independent of graft size. When mice were treated with high-dose lipopolysaccharide-W three months after irradiation and bone marrow transplantation, CFU-F numbers decreased to hardly detectable levels within one day, and then recovered to normal numbers four weeks later--whereas radiation control mice still had low CFU-F numbers. These data suggest that after lethal total-body irradiation the stroma still contained viable fibroblastic cells that had lost their in vitro colony-forming capacity as a result of radiation damage. In consequence there was no need for replacement of these fibroblastic cells by donor-derived or host-derived CFU-F. Only depletion of CFU-F from the bone marrow, as was induced with lipopolysaccharide, stimulated repopulation of the stroma with colony-forming fibroblastic cells.