It has been reported that granulocyte-colony stimulating factor (G-CSF) and granulocyte-macrophage-colony stimulating factor (GM-CSF) can mobilize endothelial progenitor cells (EPCs) in bone marrow cells (BMCs) into peripheral blood (PB) in vivo. Previously, we also reported that macrophage-colony stimulating factor (M-CSF) can mobilize EPCs into PB, which results in the rapid recovery of blood flow in induced-ischemia limbs by augmenting the number of intramuscular capillaries in vivo. In the present study, we demonstrate that M-CSF and/or G-CSF can increase EPCs from lineage (CD3, B220, Gr-1, Mac-1, CD11c, Ter119, NK1.1 or CD31)-negative BMCs in vitro. Lineage-negative BMCs were cultured with or without M-CSF and/or G-CSF. Three days after culture with M-CSF and/or G-CSF, the number of Flk-1+/CD45−, Sca-1+/CD45−, CD31+/CD45− or CD146+/CD45− cells increased in comparison with no cytokines. When the cultured BMCs with or without G-CSF and/or M-CSF were intravenously injected into ischemia-induced hindlimbs of mice, the number of intramuscular capillaries in the ischemia-induced legs increased; BMCs cultured with G-CSF and/or M-CSF were more effective than those of cytokine non-treated BMCs. These results suggest that M-CSF and/or G-CSF can induce the differentiation of BMCs into EPCs, even in vitro.

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