大鼠脑缺血再灌注早期血脑屏障通透性的变化

Changes of blood-brain barrier permeability in early stage of cerebral ischemia-reperfusion injury in rats

摘要:

目的 探讨大鼠脑缺血再灌注早期血脑屏障(BBB)通透性的变化。方法 采用随机数字表法,将大鼠分为6组:假手术(Sham)组、缺血1 h组,缺血2 h组、缺血2 h再灌注0.5 h组、缺血2 h再灌注1 h组和缺血2 h再灌注2 h组。采用大脑中动脉线栓法制作局灶性脑缺血再灌注模型,透射电子显微镜下观察,并经鼠尾静脉注射I¹²⁵-神经生长因子(I¹²⁵-NGF),观察脑组织中I¹²⁵-NGF渗入量的变化。采用脑组织冠状冰冻切片放射自显影技术观察I¹²⁵-NGF在脑组织中的范围。结果 与Sham组比较,缺血1 h组,缺血2 h组、缺血2 h再灌注0.5 h组、缺血2 h再灌注1 h组和缺血2 h再灌注2 h组大鼠的¹²⁵I-NGF γ计数均显著增高,差异具有统计学意义(P＜0.05)。与Sham组比较,缺血2 h组内皮细胞管腔面的微绒毛数目明显增多,内皮细胞轻度皱缩,胞质中胞饮小泡正在形成,内皮细胞胞质中部分线粒体轻度肿胀,星形胶质细胞足突轻度肿胀,细胞外间隙轻度扩大。缺血2 h再灌注2 h组内皮细胞核明显皱缩,内皮细胞线粒体肿胀模糊,基质膜增宽,密度变淡,星形胶质细胞足突肿胀,细胞外间隙扩大,水肿液积聚。Sham组脑室部有少量的I¹²⁵-NGF渗入；缺血2 h组的脑室和部分皮层损伤中心有I¹²⁵-NGF渗入；缺血2 h再灌注2 h组的脑室、损伤侧大脑皮层及皮层下组织均有较多I¹²⁵-NGF渗入。结论 大鼠脑缺血再灌注早期有BBB的破坏,随缺血再灌注时间延长,BBB通透性加剧。

Abstract:

Objective To study the changes of the permeability of blood-brain barrier (BBB) in the early stage after cerebral ischemia-reperfusion (I/R) injury in rats. Methods Thirty rats were randomly divided into 6 groups:sham group, ischemia for 1 h group (I1h), ischemia for 2 h group (I2h), ischemia for 2 h followed by reperfusion for 0.5 h (I2h/R0.5h), ischemia for 2 h followed by reperfusion for 1 h (I2h/R1h), and ischemia for 2 h and then reperfusion for 2 h (I2h/R2h). The cerebral ischemia-reperfusion model of middle cerebral artery occlusion (MCAO) was established by middle cerebral artery occlusion. The BBB structure was observed with transmission electron microscopy. After I¹²⁵ labeled nerve growth factor (I¹²⁵-NGF) was injected into the rats by tail vein, its permeation through the BBB was determined by counting γ-rays. Autoradiography was used to observe the distribution of I¹²⁵-NGF in the involved areas in the frozen section of brain coronal tissues. Results Compared with that in rats of the sham group, the content of I¹²⁵-NGF was significantly higher in the rats from the I1h, I2h, I2h/R0.5h, I2h/R1h, and I2h/R2h groups (P<0.05). Compared with sham group, the I2h group displayed that the number of microvilli on the luminal surface of endothelial cells was increased significantly, and the endothelial cells were slightly shrunken, with the pinocytotic vesicles formed in the cytoplasm and slightly swollen mitochondria. And the astrocytes were observed with mild swollen foot processes and wilder extracellular space. In the I2h/R2h group, the endothelial cells were swollen and blurred, with wrinkled nucleus and larger gap, and the astrocytes were with mild swollen foot processes, wilder extracellular space, and accumulated edema fluid. I¹²⁵-NGF was slightly infiltrated into the ventricle of the sham group, moderately into the ventricle and involved cortex of the I2h group, but largely into the ventricle, involved cortex and subcortical tissues in the I2h/R2h group. Conclusion BBB is impaired at the early stage of cerebral ischemia-reperfusion injury in rats. With the elapse of ischemia/reperfusion duration, the integrity of the BBB has deteriorated more severely.