Objective      To investigate the effect and mechanism of granulocyte-colony stimulating factor (G-CSF) on mobilization of bone marrow stem cells

angiogenesis and nerve repair in infarct brain tissues of rats with focal cerebral ischemia.       Methods      The rat models of middle cerebral artery occlusion (MCAO) were constructed using filament occlusion method

and 60 MCAO model rats were randomly divided into a control group (n=12) and a G-CSF group (n=48). The rats of the G-CSF group were subcutaneously injected with G-CSF [2

10

50 and 250 μg/(kg·d)] for 1

3

5 and 7 d

and the rats of the control group were injected with the same amount of normal saline. The neurological scale was evaluated. The number of mononuclear cells (MNCs) in peripheral blood was counted. The mRNA expressions of CD31 and CXCR4 were detected by RT-PCR. The expressions of CD31

CD133 and stromal cell-derived factor 1 (SDF-1) were detected by immunohistochemistry.       Results      Compared with the control group

the neurological function of the rats was improved significantly (P0.05)

and the number of MNCs in peripheral blood increased significantly in the G-CSF group. The mRNA expression of CD31 and CXCR4 in MNCs increased in a time-dependent manner in the low-dose G-CSF groups [2 and 10 μg/(kg·d)]. In the high-dose G-CSF groups [50 and 250 μg/(kg·d)]

the mRNA expression of CD31 and CXCR4 in MNCs increased in a dose-dependent manner in the first 3 d

but the increase was gradually weakened from the 4th to the 7th day. The expression of CD31

CD133 and SDF-1 in the brain tissues of the G-CSF group significantly increased as compared with those of the control group.       Conclusion      The symptoms of MCAO model rats can be relieved by G-CSF

which can induce the mobilization of bone marrow stem cells in peripheral blood and upregulate the SDF-1 expression in brain tissues of MCAO model rats to promote angiogenesis and nerve repair.