Neovascularization And Its Mechanisms In Focal Cerebral Ischemia/reperfusion Model In Rats

Objects Research found that neovascularization which may contribute to neurologic recovery does exist in focal ischemia/reperfusion brain , vascular endothelial growth factor(VEGF) and bone marrow derived endothelial progenitor play important roles in new blood vessel formation. So we observed VEGF expression in plasma and brain, and studied roles of circulating CD34+ monocytes and AC133+ cells in neovascularization after focal cerebral ischemia/reperfusion in rats. Methods Right middle cerebral artery suture occlusion model was used. 65 adult SD male rats were randomly divided into 3 groups. They were control, sham-control and animal models which included 1-hour (1h), 3h, 6h, 12h, 24h, 2-day (2d), 3d, 4d, 7d, 14d, 28d reperfusion groups. After right middle cerebral artery occluded, the rats were suffered from ischemia for 2 hours, then reperfusion was allowed for different time as mentioned above before decapitation. Circulating CD34+ cells were detected by cytoflowmetric analysis and plasma VEGF concentration were determined by using a quantitative ELISA technique in groups except 28d reperfusion group. Cerebral VEGF protein expression in 6h, 12h, 24h, 3d, 7d reperfusion groups and cerebral AC133 antigen expression in 2d, 3d, 4d, 7d reperfusion groups were tested by immunohistochemistry. AC133mRNAexpression was tested by RT-PCR in 3d> 7d reperfusion groups. Cerebral vessels were observed in 28d reperfusion group by FITC-dextran perfusion. Result 1. Reperfusion 28 days later, total cerebral vessel areas in infarct hemisphere were more than vessel areas in contralateral hemisphere by 24.79%. 2. Plasma VEGF concentration ranged from 0 to 90pg/ml during lh to 14d. VEGF appeared in plasma in 6h, went down in 12h, reached its peak in 3 days, disappeared by 7 days. 3. Brain VEGF was mainly expressed in neurons, glial cells and endothelial cells in ispilateral hemisphere of infarction. Reperfusion 6 hours, VEGF expression was observed and reached its peak after 7 days. 4. There was no influence on circulating CD34+ cells in rat MCAO models from lh to 2 days after reperfusion. But circulating CD34+ cells sharply decreased from 3 to 7 days and returned to basal values on the 14th day. 5. AC 133 antigen expression was only observed in endothelial cells in areas around infarct core in 4 days. 6. We found that AC133mRNA expressed in normal rat brain tissue. AC133mRNA expression may increase in ispilateral hemisphere of infarction after cerebral ischemia. Compared AC133mRNA expression increasing in ispilateral hemisphere in 7d group with that in 3d group, the former increased by twice (39.1%vsll.8%). Conclusion 1. VEGF plays a vital role in neovascularization after cerebral ischemia/reperfusion. Plasma and tissue VEGF may have close relationship in neovascularization. 2. Circulating CD34+ cells and AC 133 antigen expression in rat MCAO models were probably studied for the first time. We may initially find that AC133mRNA may up-regulate after cerebral ischemia. We hypotheses that circulating CD34+ cells and AC 133 antigen may take part in vessel repair and neovascularization in rat MCAO models.