目的 探讨微小RNA（miR)-98-5p靶向Kruppel样转录因子9(KLF9)对大鼠心肌缺血/再灌注（MI/R）损伤的保护作用。  方法 50只大鼠随机分为假手术组、模型组、miR-98-5p agomir组、agomir-NC组及miR-98-5p agomir+pcDNA-3. 1-KLF9组，每组10只。通过冠状动脉结扎法建立MI/R注模型。HE染色观察心肌组织病理情况；TUNEL检测心肌组织细胞凋亡情况；ELISA检测血清肌酸激酶(CK)、肌酸激酶同工酶(CK-MB)、乳酸脱氢酶(LDH)含量；Real-time PCR检测心肌组织miR-98-5p、KLF9 mRNA表达水平；Western blotting检测心肌组织KLF9、Bax和JAK2/STAT3信号通路相关蛋白表达；双荧光素酶报告实验验证miR-98-5p与KLF9的关系。  结果 与假手术组相比，模型组大鼠心肌细胞排列较乱，出现坏死；心肌组织细胞凋亡率、血清CK、CK-MB、LDH含量均升高，心肌组织miR-98-5p表达水平下降，KLF9 mRNA和蛋白及p-JAK2和p-STAT3蛋白表达均升高（P<0.05）。过表达miR-98-5p后，大鼠心肌细胞排列较为整齐，心肌细胞坏死减少；心肌组织细胞凋亡率、血清CK、CK-MB、LDH含量及心肌组织p-JAK2、p-STAT3蛋白表达均下降（P＜0.05）。双荧光素酶报告实验结果验证KLF9是miR-98-5p的靶基因。过表达KLF9逆转了miR-98-5p agomir对心肌损伤大鼠产生的作用。  结论 MiR-98-5p靶向KLF9改善MI/R大鼠心肌损伤，其机制可能与miR-98-5p调控JAK2/STAT3信号通路抑制心肌细胞凋亡相关。

Objective  To investigate the protective effect of micro RNA(miR)-98-5p targeting Kruppel-like factor 9(KLF9) against myocardial ischemia-reperfusion(MI/R) injury in rats.   Methods  Totally 50 rats were randomly divided into sham operation group, model group, miR-98-5p agomir group, agomir-NC group, and miR-98-5p agomir+pcDNA-3. 1-KLF9 group, 10 in each group. MI/R model was established by coronary artery ligation. The pathological changes of myocardial tissue were detected by HE staining. The myocardial apoptosis were detected by TUNEL. The levels of creatine kinase (CK), creatine kinase isoenzymes (CK-MB) and lactate dehydrogenase (LDH) in serum were detected by ELISA. The expression levels of miR-98-5p and KLF9 mRNA were detected by Real-time PCR. The expression of KLF9, Bax and JAK2/STAT3 pathway relative protein were detected by Western blotting. Dual luciferase assay verified the relationship between miR-98-5p and KLF9.  Results  Compared with the sham operation group, the arrangement of myocardial cells in the model group was disordered, and the myocardial cells appeared necrosis. The apoptosis rate of myocardial cells, serum CK, CK-MB and LDH contents increased, the expression level of miR-98-5p decreased, and the expression levels of KLF9 mRNA and protein, p-JAK2 and p-STAT3 protein increased (P<0.05). After the overexpression of miR-98-5p, the myocardial cells arranged more orderly and the myocardial cell necrosis decreased. The apoptosis rate of myocardial tissue, the contents of CK, CK-MB and LDH in serum and the expression of p-JAK2 and p-STAT3 protein were decreased (P<0.05). The result  of dual luciferase assay showed that KLF9 was the target gene of miR-98-5p. The overexpression of KLF9 reversed the effects of miR-98-5p agomir on myocardial injury.  Conclusion  MiR-98-5p targeting KLF9 can improve the myocardial injury of MI/R rats. The mechanism may be related to the regulation of JAK2/STAT3 signal pathway by miR-98-5p which inhibit myocardial cell apoptosis.