Effect of recombinant human macrophage-colony stimulating factor on marrow, splenic, and peripheral hematopoietic progenitor cells in mice

The effects of human macrophage colony-stimulating factor (M-CSF) on marrow, splenic, and peripheral progenitor cells (CFU-M, CFU-GM, and CFU-G) were investigated in mice administered recombinant human M-CSF (8-4,000 micrograms/kg). Single injection of 4,000 micrograms/kg of M-CSF resulted in a decrease in the number of marrow progenitor cells (CFU-M, CFU-GM, and CFU-G) on day 2 followed by a gradual increase, returning to the original level on day 4 or 5. In contrast, each type of splenic progenitors tested for started to increase markedly on day 2, reaching a level 4- to 15-fold higher than that of the basal value on day 3 or 4. Peripheral CFU-M, CFU-GM, and CFU-G also increased on day 2. In addition, administration of 800 micrograms/kg of M-CSF in mice caused a decrease in marrow CFU-G, as well as an increase in splenic CFU-G. The present results indicate that treatments of mice with pharmacological concentrations of human M-CSF affect the number of progenitor cells not only of monocyte/macrophage lineage but also of granulocyte lineage. Also, the coincidence between decrease of marrow progenitor cells and increase of splenic and peripheral progenitor cells suggests that the progenitor cells are released from bone marrow to peripheral blood and reseeded to the spleen by the action of M-CSF.