Cardiac-specific overexpression of miR-122 induces mitochondria-dependent cardiomyocyte apoptosis and promotes heart failure by inhibiting Hand2.

MicroRNA-122 (miR-122) is one of several microRNAs elevated in heart failure patients. To investigate the potential role and mechanism of miR-122 in heart failure, we constructed a transgenic mouse overexpressing miR-122 in the heart. This mouse exhibited cardiac dysfunction (as assessed by transthoracic echocardiography), morphological abnormalities of the heart and cardiomyocyte apoptosis characteristic of heart failure. Mechanistically, we identified the Hand2 transcription factor as a direct target of miR-122 using a dual-luciferase reporter assay. In Tg-miR-122 mice and H9C2 cells with miR-122 mimics, we detected apoptosis and increased expression of dynamin-related protein-1 (Drp1). This effect was blocked with prior knockdown of Hand2 in vitro. Our work suggests that miR-122 causes cardiomyocyte apoptosis by inhibiting Hand2 and consequently increasing Drp1-mediated mitochondrial fission. Such a mechanism likely contributes to heart failure and so modulating this pathway could be therapeutically valuable against heart failure.