Inhibition of myocardial remodeling through miR-150/TET3 axis after AMI

Current studies have suggested that miRNA is beneficial in inhibiting myocardial remodeling after myocardial infarction (AMI), however, its underlying mechanism is unclear.

We aimed to investigate whether miR-150 can inhibit myocardial remodeling after myocardial infarction and whether this process is regulated by the miR-150/TET3 pathway.

On the first day, C57BL/6 AMI mice(n = 15) were administrated with miR-150, and another 15 AMI mice were administrated with the same volume of control Agomir. Left ventricular ejection fraction (LVEF%) and myocardial remodeling were compared after one week; TET3 (ten-eleven translocation 3) and VEGF-α (vascular endothelial growth factor-α) were also determined in the infracted heart simultaneously. The neovascularization in the infarcted area at day 21 was compared through CD31 using fluorescence microscopy; Activated monocytes stimulated with LPS were transfected with miR-150. Laser scanning confocal microscopy was used to detect the intracytoplasmic imaging of miR-150 in Ly6C^high monocytes. Expression of the miR-150 in the monocytes was measured using Q-PCR. After 48 h, the proportion of Ly6C^high/low monocytes was determined using flow cytometry. Expression of TET3 in Ly6C^high/low monocytes was measured using Q-PCR and Western blot. After the downregulation of TET3 specifically, the levels of Ly6C^high/low monocytes were further determined.

We first observed an increased trend of mice survival rate in the miR-150 injection group, but it didn't reach a statistical difference (66.7% vs. 40.0%, p = 0.272). However, AMI mice administrated with miR-150 displayed better LVEF% (51.78%±2.90% vs. 40.28%±4.20%, p<0.001) and decreased infarct size% (25.47 ± 7.75 vs. 50.39 ± 16.91, p = 0.002). After miR-150 was transfected into monocytes, the percentage of Ly6C^low monocytes increased significantly after 48 h (48.5%±10.1% vs. 42.5%±8.3%, p < 0.001). Finally, Western blot analysis (0.56 ± 0.10/β-actin vs. 0.99 ± 0.12/β-actin, p < 0.001) and real-time PCR (1.09 ± 0.09/GAPDH vs. 2.53 ± 0.15/GAPDH, p < 0.001, p < 0.001) both confirmed decreased expression of TET3 in monocytes after transfection with miR-150. After the downregulation of TET3 specifically, Ly6C^low monocytes showed a significant increase (16.73%±6.45% vs. 6.94%±2.99%, p<0.001, p < 0.001).

miR-150 alleviated myocardial remodeling after AMI. Possible mechanisms are ascribed to the regulating of TET3 and VEGF-α in inflammatory monocytes.