Objectives MicroRNAs, as one of key regulators for post-transcriptional gene control, have shown to be involved in cardiovascular diseases. This study aimed to investigate the roles of miR-378 in regulation of cardiac hypertrophy and cardiac fibrosis stimulated by pressure overload.
Methods To construct cardiac remodelling mice models, pressure overload was imposed on the heart of C57B/L6 mice (8 weeks) by constriction of transverse aortic banding (TAC). Chemically modified oligonucleotides miRNA mimics (miR-378-Agomir) and inhibitors (miR-378-Antagomir) treatment started 24 h after TAC by intravenous injections on two consecutive days. Mice were randomly divided into four groups: 1) the TAC group; 2) the TAC-Agomir group; 3) the TAC- Antagomir group; 4) the Sham operation group. Mice after sham or 2 weeks TAC operation were subjected to hemodynamic and echocardiographic measurement. Tissue and serum miR-378 expressions were detected by TaqMan MicroRNA Assay Kit. ANP, BNP, β-MHC, collagen I and collagen III was measured by Real-time PCR. ERK1/2, p-ERK1/2, MMPs and α-SMA expression were analysed by western blotting. Collagen was assessed by immunohistochemistry.
Results We found that miR-378 has a high expression pattern in the heart. After two-week acute pressure overload, the TAC group exhibit prominent cardiac hypertrophic responses and decreased expression of miR-378(p < 0.05) comparing with the sham group. In vivo overexpression of miR-378 in TAC-Agomir group markerly inhibited cardiac hypertrophy, accompanied with downregulation of fetal gene ANP, BNP and β-MHC compared to that of TAC group. Howerver, inhibition of endogenous miR-378 by an infusion of an antagomir caused sustained cardiac hypertrophy, associated with a reinduction of fetal gene expression to a less extent. The p-ERK level was also downregulated in TAC-Agomir group and upregulated in TAC- Antagomir group. In part of cardiac fibrosis, we found that the over-expression of miR-378 of TAC-Agomir group reduced the expression of col I, col III, MMP2, MMP9 and α-SMA(p < 0.05) compared to that of TAC group, whereas down regulation of endogenous miR-378 with anti-miRs promoted collagens and MMPs expression.
Conclusions These findings reveal orchestrating regulatory roles for miR-378 in pressure-overload induced cardiac remodeling. It suggests that miR-378 not only suppresses cardiac hypertrophy by regulating fetal genes expression and ERK1/2 signaling pathway but also controls fibrosis-related genes expression in the heart.