Effect of miR-26a on diabetic rats with myocardial injury by targeting PTEN

S.-S. Cai, X.-W. Tao, Y. Long, K. Xia, Y. Zhang

Department of Cardiovascular Medicine, 2Department of Neonatal Medicine; Wuhan Children’s Hospital (Wuhan Maternal and Child Healthcare Hospital), Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China. 1539210298@qq.com

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• Geriatrics

OBJECTIVE: To investigate the effect of micro ribonucleic acid (miR)-26a on diabetes-induced myocardial injury in rats by targeting the gene of phosphate and tension homology detected on chromosome ten (PTEN).

MATERIALS AND METHODS: Male Wistar rats aged 8-9 weeks old were divided into the control group (n=10), GK group (n=10), and miR-26a agomir group (n=10) according to the body weight. MiRanda and TargetScan target gene prediction software were used to predict and analyze the target gene of miR-26a-5p. The expressions of miR-26a and PTEN in the myocardial tissues of the diabetic rats were detected by quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR). Hematoxylin-eosin (HE) staining was adopted to observe the pathological changes in the myocardial tissues. In addition, the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay was conducted to detect myocardial apoptosis, while the expression of PTEN protein was detected via immunohistochemistry, and the protein expressions of PTEN, b-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), and cysteinyl aspartate specific proteinase-3 (Caspase-3) were tested by Western blotting.

RESULTS: TargetScan database analysis results showed that miR-26a-5p and PTEN 3’UTR had 6 pairs of complementary bases with the same sequence. Compared with those in the control group, the messenger RNA (mRNA) expression of PTEN in the GK group was notably increased (p<0.05), while that of miR-26a was substantially reduced (p<0.05). In comparison with those in the GK group, the mRNA expression of PTEN was significantly decreased, but that of miR-26a was significantly raised in miR-26a agomir group (p<0.05). Through observation under an optical microscope, it was manifested that in the control group, the myocardial fibers were intact with clear texture but no fracture, and the solid necrosis did not appear in myocardial cells. In the GK group, the myocardial fibers were disorderedly arranged and incomplete with an unclear edge and burrs. The myocardial fibers in the miR-26a agomir group were more regular, with less breakage and solid necrosis. According to TUNEL staining results, the TUNEL-stained brown granules in rats in the GK group were remarkably increased, relative to the control group (p<0.05). Compared with the GK group, miR-26a agomir group had markedly decreased the TUNEL-stained brown particles (p<0.05). It was found in immunohistochemical results that PTEN protein was in lighter color after staining in the control group, with a clear myocardial cell stripe structure. Compared with that in control group, PTEN protein in the GK group was in deeper color after staining, and in comparison with that in the GK group, the color of PTEN protein in miR-26a agomir group became significantly lighter. Moreover, the Western blotting results demonstrated that, compared with those in the control group, the Caspase-3 and Bax protein expressions in the GK group were significantly raised, while Bcl-2 protein expression was notably reduced (p<0.05). Besides, in comparison with the GK group, miR-26a agomir group evidently elevated Caspase-3 and Bax protein expressions and a notably increased Bcl-2 protein expression (p<0.05).

CONCLUSIONS: We showed that miR-26a can protect against myocardial injury in diabetic rats by regulating PTEN.

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