骨形态发生蛋白-7对大鼠脑缺血再灌注后Caspase-3表达的影响

Effect of bone morphogenetic protein-7 on expression of Caspase-3 in rats with cerebral ischemic reperfusion injury

目的观察骨形态发生蛋白-7(BMP-7)对大鼠局灶性脑缺血再灌注损伤神经细胞凋亡的影响及其机制。方法将40只SD雄性大鼠随机分为实验组、对照组和假手术组,采用改良线栓法制作大脑中动脉栓塞缺血再灌注(MCAO/R)模型,实验组在缺血2h再灌注后尾静脉注射BMP-7(0.1mg/kg)250μl,对照组和假手术组尾静脉注射等量生理盐水,运用Bederson评分法进行神经功能缺失评分。再灌注24h后将大鼠处死,采用2,3,5-氯化三苯基四氮唑(TTC)染色法观察梗死灶范围,并计算梗死灶体积占半球体积的百分比;HE染色观察脑组织病理变化,原位缺口末端标记法(TUNEL)计数神经元凋亡数量,免疫组织化学染色观察缺血脑组织内Caspase-3表达。结果 BMP-7组大鼠Bederson评分(1.7±0.5)比对照组(2.7±0.5)明显降低(t=4.66,P<0.01),脑梗死体积百分比(7.6±1.4)比对照组(22.3±4.5)明显降低(t=6.98,P<0.01)。与对照组相比,HE染色显示BMP-7组大鼠缺血侧大脑皮质脑组织损伤明显减轻。BMP-7组缺血侧大脑皮质、纹状体及海马TUNEL阳性细胞数(分别为3.6±0.6、7.4±1.1、5.0±0.7)明显低于对照组同一区域(分别为13.4±1.1、17.8±1.5、15.4±1.1,P<0.01)。BMP-7组缺血侧大脑皮质、纹状体及海马Caspase-3阳性细胞数(分别为7.6±0.9、5.8±0.8、10.6±1.1)明显低于对照组同一区域(分别为15.4±0.6、14.0±1.2、17.2±0.8,P<0.01)。结论 BMP-7可通过下调Caspase-3表达而抑制大鼠脑缺血再灌注损伤引起的细胞凋亡,起到神经保护作用。

Objective To explore the effect and the mechanism of bone morphogenetic protein-7 （BMP-7） on neuronal apoptosis in the rat brain after cerebral isehemic reperfusion injury. Methods Ten rats from 40 adult healthy male Sprague-Dawley rats received sham-operation, and the other 30 rats were subjected to middle cerebral artery occlusion （ MCAO ） for 2 hours, of which the 20 successfully modeled rats were equally randomized into the control group and the treatment group, 10 rats each group. The rats in the treatment group were intervened with 250μl of BMP-7 （0. 1mg/kg） via caudal vein injection, while the rats in the control group and the sham-operative group were intervened with equal volume of normal saline. Animals were sacrificed at the 24th hour after reperfusion. Neurological deficits were evaluated by Bederson method, and the infarction volume of brain was investigated by 2,3,5-triphenyl tetrazolium chloride coloring. Pathological changes in the lesion site were investigated by HE coloring. The neuronal apoptosis was detected by TUNEL staining and the expression of Caspase-3 with the immunohistochemistry method. Results In the treatment group, the Bedersonscore （1.7±0.5, t=4.66, P〈0.01） and focusinfaretion [（7.6±1.4）%, t=6.98, P 〈0.01] were lower than those in the control group [ 2. 7± 0. 5, （22.3 ± 4. 5 ） % ]. Damage of the ischemia brain was significantly lessened in the BMP-7 treatment group. The number of TUNEL positive cells in the cortex （3.6 ± 0. 6）, striatum （7.4± 1.1 ） and hippoeampus （5.0 ±0. 7） of the treatment group were lower than those in the control group （13.4 ±1.1,17.8 ± 1.5,15.4＋1.1,P〈0.01）. The number of Caspase-3 positive cells in the cortex （7.6±0.9）,striatum （5.8 ±0.8） and hippocampus （ 10.6 ± 1.1 ） of the treatment group were lower than those in the control group （ 15.4 ＋ 0. 6, 14. 0 ± 1.2, 17.2±0. 8, P 〈 0. 01 ）. Conclusion BMP-7 may down-regulate the expression of Caspase-3, and inhibit the neuronal apoptosis in order to protect animals against ischemia injury.