ACE2过表达对大鼠心肌梗死后心室重构的影响

Effect of overexpression of angiotensin converting enzyme 2 on ventricular remodeling after myocardial infarction in rats

目的探讨携带ACE2基因的重组腺病毒载体(Ad-ACE2)转染对大鼠心肌梗死(MI)后心室重构的影响及其机制。方法 Sprague-Dawley(SD)大鼠75只,8～10周龄,体质量200～250 g,结扎左冠状动脉前降支,建立SD大鼠MI模型,完全随机分为心梗组(MI组)、生理盐水组(NS组)、空载体组、Ad-ACE2组(转染Ad-ACE2组),并另设假手术组(n=15)。NS组、空载体组、Ad-ACE2组分别以直接心肌内注射方式沿梗死周边区选取5个点注射NS、Ad-EGFP及Ad-ACE2,假手术组及MI不予以任何注射。术后4周检测并评价相关指标。结果①与假手术组比较,Ad-ACE2组ACE2蛋白表达增加(P<0.05)。②与MI组比较,Ad-ACE2组肌纤维排列紊乱,肌丝断裂,细胞核固缩、碎裂等现象明显减轻;Ⅰ、Ⅲ型胶原表达均减少。③免疫组化与ELISA结果显示:与假手术组比较,MI组、NS组、空载体组及Ad-ACE2组AngⅡ、Ang-(1-7)蛋白表达均增高(P<0.05);与MI组比较,Ad-ACE2组AngⅡ蛋白表达降低(P<0.05),Ang-(1-7)蛋白表达增高(P<0.05)。④免疫印迹结果显示:与MI组比较,Ad-ACE2组MMP-9蛋白表达降低(P<0.05),TIMP-1蛋白表达水平增加(P<0.05),且MMP-9/TIMP-1的比值降低。⑤与假手术组比较,MI组、NS组、空载体组的TGF-β和α-SMA表达增高(P<0.05),而Ad-ACE2组表达降低(P<0.05)。结论过表达ACE2可改善心肌纤维化,缓解心室重构,其机制可能与其调节肾素-血管紧张素系统,下调MMP-9、TGF-β及α-SMA的表达,维持MMP-9/TIMP-1的比例平衡有关。

（ Ad-ACE2 ） on the Objective To determine the effect of adenovirus-angiotensin converting enzyme 2 ventricular remodeling after myocardial infarction （MI） in rats. Methods A total of 75 Sprague-Dawley（SD） rats, at an age of 8 to 10 weeks, weighing 200 to 250 g were randomly divided into MI model group （n = 60） and sham operation group （n = 15 ）. MI model was induced by the ligation of the anterior descending branch of left coronary artery. Then the MI rats were randomly treated with normal saline, vector, and Ad-ACE2, with 15 rats in each group. The left 15 MI rats served as model control. The rats from above treatment groups were injected intramyocardial directly into normal saline, Ad-EGFP and Ad-ACE2 in 5 different points along the infarct borders respectively. Rats in the model group and sham operation group received no such injection. The relative ventricular remodeling indexes after 4 weeks were evaluated. Results Compared with sham operation group, ACE2 protein was highly expressed in Ad-ACE2 group（P 〈0. 05 ）. The changes of muscle fiber disorder, myofilament fracture, nuclear condensation, and nuclear fragmentation, and the elevated expression levels of type I and Ill collagens in the model control were improved significantly, and decreased in Ad-ACE2 group. Immunohistoehemical staining and ELISA indicated the expression levels of Ang Ⅱand Ang-（1-7） were increased in MI, normal saline group, vector and Ad-ACE2 groups than in the sham operation group （P 〈 0. 05 ）, and that of Ang Ⅱ was decreased, while that of Ang-（ 1-7 ） protein was increased in AdACE2 group than in MI group（P 〈 0.05 ）. Western blotting showed that Ad-ACE2 injection resulted in an obvious decrease in the MMP-9 expression, a significant increase in the TIMP-1 expression, and a following reducein the ratio of MMP-9/TIMP-1 when compared with MI control （P 〈 0. 05 ）. Compared with sham operation group, the protein levels of TGF-13 and oL-SMA were consistently increased in MI group, normal saline group and vector group, and decreased in Ad-ACE2 group （P 〈 0.05 ）. Conclusion The over-expression of ACE2 ameliorates ventricular fibrosis and attenuates ventricular remodeling after MI, which probably through regula- ting renin-angiotensin system, down-regulating MMP-9, TGF-β, and α-SMA, and maintaining the balance of MMP-9/TIMP-1.