To investigate the effects of long non-coding ribonucleic acid (lncRNA) metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) on myocardial ischemia/reperfusion (I/R) injury in rats and its mechanism, and to provide a certain reference for the clinical prevention and treatment of myocardial infarction.A total of 60 male Sprague-Dawley rats were divided into 3 groups using a random number table, including the Sham group (n=20), I/R group (n=20) and I/R + MALAT1 small interfering RNA (siRNA) group (n=20). An I/R model was established by means of recanalization after ligation of the left anterior descending coronary artery of the rats. The rats in the I/R + MALAT1 siRNA group were used to establish a model of MALAT1 knockdown by injecting MALAT1 siRNA from the tail vein. The myocardial infarction area in each group was detected via 2,3,5-triphenyl tetrazolium chloride (TTC) staining. The ejection fraction% (EF%) and fractional shortening% (FS%) of the heart in each group were measured through echocardiography. Hematoxylin and eosin (H&E) staining was adopted to determine the morphological changes in myocardial cells in each group. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining was performed to detect the apoptosis levels of myocardial cells and fibroblasts in the cardiac tissues in each group, and Western blotting assay was conducted to measure the expression levels of apoptosis-related proteins [B-cell lymphoma-2 (Bcl-2) and Bcl-2-associated X protein (Bax)]. In addition, the content of β-catenin in the three groups of rats was determined via immunohistochemical staining. Finally, the impacts of MALAT1 siRNA on the expression level of β-catenin protein were detected using Western blotting assay.MALAT1 siRNA could prominently ameliorate the I/R-induced cardiac insufficiency in the rats and improve the EF% and FS% of the heart (p<0.05). Moreover, MALAT1 siRNA was able to remarkably inhibit the I/R injury-induced myocardial infarction, reducing the infarction area from (59.54±3.45) to (24.85±1.30; p<0.05). The results of the H&E staining indicated that compared with those in the I/R group, the myofilaments of the myocardial cells were well-arranged, the degrees of degradation and necrosis of the myofilaments declined, and the cellular edema was relieved markedly in the I/R + MALAT1 siRNA group. It was shown in the results of immunohistochemistry and Western blotting that MALAT1 siRNA could notably reverse the I/R-induced up-regulation of β-catenin expression (p<0.05).MALAT1 knockdown can significantly ameliorate the I/R-induced myocardial injury and improve the cardiac function of the rats, whose mechanism is probably correlated with the inhibition of MALAT1 siRNA on β-catenin. Therefore, MALAT1 siRNA is expected to become a new target for the treatment of myocardial infarction.
