Growth of mouse and human bone marrow in diffusion chambers in mice. Development of myeloid and erythroid colonies and proliferation of myeloid stem cells in cyclophosphamide- and erythropoietin-treated mice.

Both murine and human bone marrow cells were cultured in plasma clots which were formed inside diffusion chambers implanted into cyclophosphamide- and saline-treated mice. After an initial fall, the number of mouse bone marrow cells and numbers of mouse myeloid stem cells (CFU-C) and agar cluster-forming units rose faster in the cyclophosphamide-treated animals. These hosts also favored formation of myeloid (CFU-D-G) and erythroid (CFR-D-E) colonies and myeloid higher than those of CFU-C from the same marrow population. These observations suggest the existence of humoral factors stimulating granulocyte progenitor cell replication and differentiation. At its best the increment of CFU-D-E number was equivalent to that caused by a single 0.1 unit erythropoietin dose. Culture of normal human marrow cells resulted in colonies in the plasma clot containing only granulocytes and macrophages. Cyclophosphamide-treated host animals were essential for human CFU-D-G development. Plating efficiency for human marrow myeloid colonies was better in the conventional in vitro agar cultures than in diffusion chambers.