MiR-21 regulates pulmonary hypertension in rats via TGF-β1/Smad2 signaling pathway

To investigate the effects of micro ribonucleic acid (miR)-21 on pulmonary hypertension (PH) in rats via regulating tumor growth factor-β1 (TGF-β1)/mothers against decapentaplegic homolog 2 (Smad2) signaling pathway and the possible underlying mechanism.

MiR-21 inhibition vector (pLKO-anti-miR-21) was first constructed. The rat model of PH was established by hypoxia feeding induction. A total of three groups were established, including: blank control group, model group and miR-21 low-expression group were set up, with 12 rats in each group. The expression level of miR-21 in lung tissues of rats in each group was detected via quantitative polymerase chain reaction (qPCR). The right ventricle systolic pressure (RVSP) and right ventricular hypertrophy index (RVHI) of rats in each group were measured. The pathological changes in lung tissues of rats were detected using hematoxylin and eosin (H&E) staining. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was used to detect the level of apoptosis in lung tissues of rats in each group. Furthermore, Western blotting was adopted to detect the expression levels of TGF-β1/Smad2 signal pathway-related proteins and apoptosis-related proteins in lung tissues of rats in each group.

Compared with blank control group, the expression level of miR-21 in lung tissues of rats in model group was significantly increased (p<0.01). Meanwhile, miR-21 expression in lung tissues of rats in miR-21 low-expression group was significantly decreased by transfection of miR-21 inhibition vector (p<0.01). The RVSP and RVHI of rats in model group were significantly higher than those of blank control group and miR-21 low-expression group (p<0.01). H&E staining results indicated that the degree of lung tissue injury in model group was remarkably higher than blank control group and miR-21 low-expression group (p<0.01). According to TUNEL staining results, the number of apoptotic cells in lung tissues of rats in model group was markedly smaller than that of miR-21 low-expression group (p<0.01). Moreover, the expression level of Caspase 3 in lung tissues of rats in model group was significantly lower than that of miR-21 low-expression group, while the expression level of B-cell lymphoma 2 (Bcl-2)/Bcl-2-associated X protein (BAX) was markedly higher. The expression levels of TGF-β1 and phosphorylated (p)-Smad2 in lung tissues of rats in model group were evidently higher than those of blank control group (p<0.01). In addition, lowly expressed miR-21 could effectively reduce the expressions of TGF-β1 and p-Smad2 (p<0.01).

MiR-21 regulates the symptoms of PH in rats by activating TGF-β1/Smad2 signaling pathway.