Objective        To determine the therapeutical  effect of endothelial progenitor cells (EPCs) transplantation on transient middle cerebral artery occlusion (tMCAO) rats

and to investigate the potential role of vascular endothelial growth factor (VEGF) in this process.       Methods        EPCs were isolated from the bone marrow of rats. After primary culture and identification by laser scanning confocal microscopy

they were transplanted into tMCAO rat model through internal carotid. The experimental rats were divided into 2 groups

PBS control group (CG) and EPCs transplantation group (EG). TUNEL were used to detect cell apoptosis in perirhinal cortex of rats which were collected in 1

3

5 and 7 d after transplantation

and immunohistochemistry and Western blotting were used to detect activated Caspase-3 and VEGF expression at the same time points.       Results       In 5 d after transplantation

EPCs transplantation resulted in a smallest number of apoptotic cells in the ischemic cortex (54.68±3.12)

lowest expression of Caspase-3 (31.24±2.73）

but highest expression level of VEGF （0.99±0.03）. All these indexes were significantly different from those of the control group at every time point (P0.05).       Conclusion       EPCs transplantation suppresses neuron apoptosis and attenuates nerve impairment after ischemia injury in tMCAO rats

which might be due to VEGF paracrine and thus decreased Caspase-3 activity.