Human bone marrow stromal cell colonies: response to hydrocortisone and dependence on platelet-derived growth factor

Long-term bone marrow cultures are dependent on the formation in vitro of an adherent cell layer that supports hematopoiesis. We have grown bone-marrow-adherent cells, termed stromal colony-forming units, or CFU-ST, as isolated adherent colonies, and examined some of their growth requirements. Bone marrow mononuclear cells separated from aspirates by density centrifugation and cultured in medium supplemented with fetal calf serum or human plasma gave rise to adherent colonies (CFU-ST). An average of 23.4 +/- 2.1 (mean +/- SEM, n = 19) CFU-ST were produced by 10(5) bone marrow mononuclear cells. CFU-ST could not be cultured from similarly prepared peripheral blood mononuclear cells. The colonies were composed of spindle cells, flat cells, and fat-containing cells, with all three types often present in the same colony, suggesting derivation from a common progenitor. Cells were negative for nonspecific esterase and factor VIII antigen. Hydrocortisone added to the cultures at concentrations of 10(-7) M induced the formation of adipose cells in the center of one-third to one-half of the colonies but did not affect CFU-ST number. Human platelet-poor plasma and platelet-rich plasma were substituted for fetal calf serum in the medium. When all determinations for four experiments were averaged, platelet-rich plasma gave 17.8 +/- 1.2 (mean +/- SEM, n = 16) colonies, whereas platelet-poor plasma gave only 0.2 +/- 0.1 colonies (n = 15). When purified platelet-derived growth factor (PDGF) was added to platelet-poor plasma, growth of CFU-ST was enhanced, and a dose-response relationship was found between size of colonies and concentration of added PDGF. Granulocyte-macrophage colony stimulating factor added to cultures had no effect on the growth of CFU-ST.