局灶性缺血预处理对脑缺血大鼠血管内皮生长因子表达及血管形成的影响

Effects of Focal Ischemia Preconditioning on VEGF Expression and Angiogenesis in Rats with Cerebral Ischemia

目的:探讨血管内皮生长因子(VEGF)在脑缺血耐受中的作用及其与血管形成的关系。方法:Wistar大鼠线栓法阻塞大脑中动脉建立局灶性缺血预处理模型,并进行神经功能评分。随机分为假手术(对照组)、非缺血预处理(NIP)组和缺血预处理(IP)组,NIP和IP组再根据不同时间窗随机分成5个亚组。分别在缺血预处理后1、3、7、14和21 d进行再次缺血2 h再灌注22 h,然后取脑检测:TTC染色测定脑梗死体积,计数微血管密度,免疫组化检测CD34和VEGF蛋白表达,原位杂交法检测VEGF mRNA表达。结果:①组间比较:IP 1、3和7 d亚组脑梗死体积较NIP组明显减小(P<0.01),其神经行为缺损评分也明显降低(P<0.05);IP 3和7 d亚组脑微血管密度明显增高(P<0.05);IP 1、3和7 d亚组VEGF蛋白及mRNA表达明显增高(P<0.05,P<0.01)。②组内比较:IP 7 d亚组微血管在缺血灶周边区分布最为密集,脑微血管密度明显高于同组内其他亚组(P<0.05);IP 3和7 d亚组VEGF蛋白表达明显增高,VEGF mRNA表达在IP 1 d即开始升高,高峰出现在IP 3 d,持续至7 d。结论:缺血预处理诱导了脑缺血耐受,缺血预处理诱导的VEGF表达增加以及血管形成在脑缺血耐受中发挥重要作用。

Aim： To investigate the effects of focal ischemia preconditioning on vascular endothelial growth factor（VEGF） expression and angiogenesis in rats with cerebral ischemia.Methods： Healthy Wistar rats were randomly assigned to three groups： sham surgery,non-ischemic preconditioning（NIP）,and ischemic preconditioning（IP）.For ischemic preconditioning,the rats were given middle cerebral artery occlusion（MCAO） for 10 min.In the IP group,rat models of pre-ischemia-reperfusion-ischemia-reperfusion were established by MCAO using the twice suture method.In the NIP group,pre-ischemia was replaced by sham surgery.Subsequently,the latter two groups were equally divided into five subgroups according to the time of first reperfusion,including 1,3,7,14,21 day subgroups.The sham surgery group received the sham surgerytwice.Brain sections were stained with TTC for surveying the volume of infraction.The expression of microvascular density（MVD）and VEGF were determined by immunohistochemical staining and in situ hybridization respectively.Results： ① Intergroup comparison： compared with the NIP group,neurologic deficit scores and infarct volume significantly decreased in the 1,3,7 day subgroups of IP group（P0.05,P0.01）.The expression of VEGF protein and mRNA significantly increased in the rat cerebral cortex and corpus striatum in the ischemic hemisphere in the 1,3,7 day subgroups of IP group.The expression of MVD significantly increased in the 3,7 day subgroups.② In the IP group,there were no significant differences in neurologic deficit scores among subgroups,infarct volume significantly decreased in the 1,3,7 day subgroups（P0.05）.The expression of MVD at 7 days,VEGF mRNA at 1,3,7 days significantly increased compared with the other groups（P0.05）.Conclusion： Increased expression of VEGF and MVD induced by IP might contribute to brain ischemic tolerance.