Characterization of human bone marrow long-term cultures.

In an attempt to more closely simulate the native hematopoietic environment, human bone marrow bony matrix was cultivated in long-term human bone marrow cultures. Sternal bone marrow curettings (i.e., 'bony matrix') were cultured with and without autologous bone marrow single cell suspensions. Fresh media were provided at weekly intervals and the 'harvested' cells were assayed for CFU-gm (i.e., the granulocyte-macrophage precursor). Bone marrow bony matrix alone was not competent to maintain CFU-gm production, although early in the culture nucleated cells and CFU-gm were recruited from the bony matrix. A dose of 850 rad of X-radiation to the bone marrow matrix damaged the hematopoietic growth-promoting effects of the adherent cell layer, which was, however, rapidly reconstituted by an inoculation of intact autologous bone marrow cells. Additional investigations revealed that, whereas the addition of hydrocortisone to this culture system did not alter the maintenance of CFU-gm, recharging the cultures with fresh autologous marrow maintained CFU-gm for 10 weeks. These data indicate that human bone marrow stroma is more sensitive to X-irradiation in vitro than in vivo, and the bone marrow hematopoietic microenvironment provided by its bony matrix seemed to be less effective in vitro than in vivo with respect to the maintenance of hematopoietic precursor cells.