西罗莫司对心肌梗死大鼠心肌纤维化的治疗作用及其机制

Effect of sirolimus on myocardial fibrosis in rats with myocardial infarction via TGF-β1/Samd signaling pathway

目的探讨西罗莫司对心肌梗死大鼠心肌纤维化的治疗作用,并分析其可能的作用机制。方法将45只雄性SD大鼠随机分为对照组、模型组、西罗莫司组各15只。对照组仅暴露冠状动脉左前降支用结扎线只穿过但不结扎;模型组、西罗莫司组用结扎冠状动脉左前降支构建大鼠心肌梗死模型。西罗莫司组术后每天给予2 mg/kg西罗莫司灌胃,对照组、模型组给予等量生理盐水灌胃。均连续给药4周。采用彩色多普勒超声心动图检测各组心脏功能;将大鼠处死取心脏,用Masson染色法测算心肌胶原容积分数(CVF),用免疫组化法检测心肌组织中Ⅰ、Ⅲ型胶原蛋白表达,用Western blotting法检测心肌组织中转化生长因子β1(TGF-β1)及TGF-β受体Smad2、7蛋白表达。结果与对照组比较,模型组左心室收缩末期直径(LVESD)、左心室舒张末期直径(LVEDD)高(P均<0.05),左室短轴缩短率(LVFS)、左室射血分数(LVEF)低(P均<0.05)。与模型组比较,西罗莫司组LVESD、LVEDD低(P均<0.05),LVFS、LVEF高(P均<0.05)。与对照组比较,模型组CVF高(P<0.05);与模型组比较,西罗莫司组CVF低(P<0.05)。与对照组比较,模型组Ⅰ型胶原、Ⅲ型胶原蛋白阳性细胞百分比高(P均<0.05);与模型组比较,西罗莫司组Ⅰ型胶原、Ⅲ型胶原蛋白阳性细胞百分比低(P均<0.05)。与对照组比较,模型组TGF-β1、p-Smad2蛋白相对表达量高(P均<0.05),Smad7蛋白相对表达量低(P<0.05)。与模型组比较,西罗莫司组TGF-β1、p-Smad2蛋白相对表达量低(P均<0.05),Smad7蛋白相对表达量高(P<0.05)。结论西罗莫司可通过抑制TGF-β1/Samd信号通路激活减轻心肌梗死大鼠的心肌纤维化。

Objective To investigate therapeutic effects of sirolimus on myocardial fibrosis rats with myocardial infarction and to explore its possible mechanism.Methods Forty-five male SD rats were randomly divided into three groups:the control group,model group,and sirolimus group,with 15 rats in each.In the control group,the left anterior descending branch of the coronary artery was only exposed to ligation line,without ligation.In the model group and sirolimus group,the left anterior descending branch of the coronary artery was ligated to construct the myocardial infarction model.The rats in the sirolimus group were given 2 mg/kg sirolimus daily after surgery,while the rats in the control group and the model group were given the same amount of normal saline by gavage.The drug was continuously given for 4 weeks.The cardiac function of each group was detected by color Doppler echocardiography.The rats were sacrificed and the hearts were harvested.Masson staining method was used to measure the myocardial collagen volume fraction(CVF),the expression of collagen type I in the myocardial tissues was detected by immunohistochemistry,and the expression of transforming growth factorβ1(TGF-β1)and TGF-βreceptor Smad2/7 in the myocardial tissues was detected by Western blotting.Results Compared with the control group,the left ventricular end-systolic diameter(LVESD)and left ventricular end-diastolic diameter(LVEDD)were higher,and the left ventricular fractional shortening(LVFS)and left ventricular ejection fraction(LVEF)were lower than those in the model group(all P<0.05).Compared with the model group,LVESD and LVEDD were lower(all P<0.05),while LVFS and LVEF were higher in the sirolimus group(all P<0.05).Compared with the control group,CVF was higher in the model group(P<0.05).Compared with the model group,CVF was lower in the sirolimus group(P<0.05).Compared with the control group,the positive cell percentages of typeⅠcollagen and typeⅢcollagen in the model group were higher(both P<0.05).Compared with model group,the positive cell percentages of typeⅠcollagen and typeⅢcollagen in the sirolimus group were lower(both P<0.05).Compared with the control group,the relative expression levels of TGF-β1 and p-Smad2 proteins in the model group were higher while the relative expression levels of Smad7 proteins were lower(all P<0.05).Compared with the model group,the relative expression levels of TGF-β1 and p-Smad2 proteins in the sirolimus group were lower and the relative expression levels of Smad7 proteins were higher(all P<0.05).Conclusion Sirolimus alleviates the myocardial fibrosis in rats with myocardial infarction through TGF-β1/Smad signaling pathway.