Differentiation of human bone marrow-derived fibroblastoid colony forming cells (CFU-F) and their roles in haemopoiesis in vitro

S ummary . Human bone marrow-derived fibroblastoid colonies have been quantitatively developed in a liquid culture. A linear relationship between cell number plated and colony number formed supports their clonal origin and hydroxyurea killing indicates that the fibroblastoid colony forming cell (CFU-F) is not in cell cycle in normal bone marrow. Adipose cells were induced in the fibroblastoid colonies by the addition of hydrocortisone (optimal concentration: 10⁻⁶ M). Furthermore, adherent layers with adipocytes provided a more favourable condition for maintaining haemopoiesis in Dexter-system cultures. These results indicate that CFU-F belongs to stromal precursor cells intimately involved in the formation of the haemopoietic microenvironment. Colony incidence of CFU-F was almost normal in most patients with aplastic anaemia, haemopoietic dysplasia and chronic myelogenous leukaemia. However, in acute myelogenous leukaemia, it varied with the stage of the disease. It is concluded that the colony assay is useful for investigating stroma/haemopoietic cell interactions.