The mobilization efficiency of granulocyte colony-stimulating factor (G-CSF) and stem cell factor (SCF) to bone marrow mononuclear cells (MNCs) in mice was observed,and the changes of CXCL12/CXCR4 signal were detected in order to find out the mobilization mechanism of stem cells.Kunming mice were randomly divided into two groups.The mice in treatment group were subjected to subcutaneous injection of G-CSF at a dose of 100 μg/kg and SCF at a dose of 25 μg/kg every day for 5 days,and those in control group were given isodose physiological saline.The MNCs were separated,counted and cultured,and the colony-forming unit-fibroblast (CFU-F) was evaluated.CD34+CXCR4+ MNCs were sorted by flow cytometry.The expression of CXCL12 protein in bone marrow extracellular fluid was detected by ELISA,and that of CXCL12 mRNA in bone marrow was measured by RT-PCR.The results showed that the counts of MNCs in peripheral blood and bone marrow were increased after administration of G-CSF/SCF (P＜0.01).The factors had a dramatic effect on the expansion capability of CFU-F (P＜0.05).Flow cytometric of bone marrow MNCs surface markers revealed that CD34+CXCR4+ cells accounted for 44.6%±8.7% of the total CD34+ MNCs.Moreover,G-CSF/SCF treatment induced a decrease in bone marrowCXCL12 mRNA that closely mirrored the fall in CXCL12 protein.In this study,it is evidenced that G-CSF/SCF can effectively induce MNCs mobilization by disrupting the balance of CXCL12/CXCR4 signaling pathway in the bone marrow and down-regulating the interaction of CXCL12/CXCR4.