Objective  To observe the change of the number of endothelial progenitor cells (EPCs) in peripheral circulation after acute middle cerebral artery occlusion/reperfusion (MCAO/R) and to evaluate the therapeutic effect of VEGF through mobilizing bone marrow-derived EPCs in treatment of mouse brain infarction after acute MCAO/R.   Methods  Totally 36 mice were randomized into MCAO/R+VEGF group

MCAO/R group and sham operation group. MCAO/R mice model was established according Longa’s method. VEGF [3.3 ng/(g·d)

for 7 d] was injected intraperitoneally to the mice of MCAO/R+VEGF group to mobilize bone marrow-derived EPCs. The other 2 group received an injection of normal saline. At days 1

4

7 during mobilization

neurological functions were evaluated and blood samples were taken from angular vein. Then the number of EPCs in peripheral circulation in MCAO/R group and MCAO/R+VEGF group was detected by flow cytometry. Mice were decapitated and brains sliced and stained with  triphenyltetrazolium chloride  (TTC) to calculate infarct volume using specific image analyzing system. Infarct volumes were calculated and compared among groups.   Results  The number of EPCs in MCAO/R+VEGF group began to increase at day 1 after treatment

and peaked at day 4 and sustained to day 7

which was significantly larger than those in MCAO/R group and sham operation group at every time point (P0.01). Neurological functions were improved significantly in both MCAO/R+VEGF group and MCAO/R group at day 7 compared with those at day 4 respectively (P0.05)

and the functions were improved significantly as early as 4 d after operation in MCAO/R+VEGF group compared with that at  1 day after operation (P0.05). There was significant difference when neurological functions were compared between MCAO/R+VEGF group and MCAO/R group at day 4 and day 7 respectively (P0.05). After VEGF treatment

infarct volume was decreased significantly in MCAO/R+VEGF group at day 4 compared with that at day 1 (P0.01)

and with the volumes of MCAO/R group at the 2 time points (P0.01). Significant difference was seen when infarct volumes were compared between MCAO/R+VEGF group and MCAO/R group at day 4 and day 7 respectively (P0.01)

and infarct volume in MCAO/R+VEGF group was smaller than that in MCAO/R group.   Conclusion  Bone barrow-derived EPCs can be mobilized by VEGF to help the recovery of injury in acute MCAO/R mice. The mobilized EPCs can increase angiogenesis to decrease infarction area and treat brain infarction.