Objective: The aim of this study was to investigate the effect of micro-ribonucleic acid-195 (miR-195) on myocardial fibrosis in hypertensive rats through the transforming growth factor beta 1 (TGFβ1)-Smad3 signaling pathway.
Materials and methods: Spontaneously hypertensive rats (SHRs) were selected in this study to establish the animal model. The content of miR-195 in the model group and control group was measured, respectively. Arterial blood pressure, liver function and myocardial function in the two groups were detected and examined. Pathological changes in rat myocardial tissues were detected via hematoxylin-eosin (HE) staining. After that, myocardial fibroblasts were collected and added with miRNA inhibitors and mimics to suppress and overexpress miR-195. Thereafter, Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and Western blotting were employed to detect the mRNA and protein expression levels of checkpoint kinase 1 (Chek1) and alpha-smooth muscle actin (α-SMA) (important molecules for proliferation and differentiation of myocardial fibroblasts), as well as the related pathway TGFβ1-Smad3. Furthermore, the effects of miR-195 on myocardial fibrosis in hypertensive rats via the TGFβ1-Smad3 signaling pathway were comprehensively observed.
Results: Serum alkaline phosphatase (ALP), glutamic pyruvic aminotransferase (ALT) and creatine kinase (CK) levels in the SHR group were significantly higher than those of the normal group. Cardiac function examination showed that SHR group had significantly reduced fractional shortening (FS, %) and ejection fraction (EF, %) in comparison with the normal group. However, systolic blood pressure, diastolic blood pressure, left ventricular end-diastolic dimension (LVEDd) and left ventricular end-systolic dimension (LVESd) were markedly elevated in the SHR group. In addition, the miR-195 expression level was remarkably reduced in hypertensive rats. Histopathological changes in rat myocardial tissues were detected through HE staining. The results showed that the normal group had orderly arranged myocardial cells. However, SHR group showed disorderly arranged myocardial cells, thickened myocardial fibers and myocardial fibrosis. RT-PCR assay results revealed that the mRNA levels of Collagen, Chek1, α-SMA, TGFβ1 and Smad3 in rat myocardial fibroblasts were significantly reduced in Mimics group (p<0.05) and increased in Inhibitors group (p<0.05). Western blotting results demonstrated that, compared with the control group, the protein levels of α-SMA, TGFβ1 and Smad3 in rat myocardial cells decreased significantly in Mimics group (p<0.05). Opposite results were observed in Inhibitors group (p<0.05). The above results suggested that overexpression of miR-195 inhibited the expressions of TGFβ1-Smad3 signaling pathway and related molecules, further repressing myocardial fibrosis.
Conclusions: MiR-195 participates in the development and progression of myocardial fibrosis in hypertensive rats through the TGFβ1-Smad3 signaling pathway. Furthermore, this can inhibit the development of myocardial fibrosis in hypertensive rats and prevent myocardial diseases.