Down-regulation of microRNA-184 contributes to the development of cyanotic congenital heart diseases.

Purpose: We aimed to investigate the roles of miR-184 in adaptation of hypoxic cardiomyocytes, as well as to elucidate the possible mechanisms of miR-184 in the development of cyanotic congenital heart diseases (CHD).

Materials And Methods: We conducted quantitative real-time polymerase chain reaction (qRT-PCR) to determine the expression of miR-184 in patients with cyanotic cardiac defects. The embryonic rat ventricular myocardial H9c2 cells were transfected with miR-184 inhibitor and negative scramble RNA. Mock group was untreated by anything. We then used MTT assay and in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling (TUNEL) to determine whether inhibition of miR-184 in vitro affect cell proliferation and apoptosis under hypoxic conditions. Besides, the expression levels of caspase-3 and caspase-9 in hypoxic H9c2 cells were determined by western blot.

Results: MiR-184 was significantly down-regulated in CHD patients with cyanotic cardiac defects. In addition, miR-184 was successfully inhibited in hypoxic H9c2 cells. Moreover, inhibition of miR-184 markedly decreased cell viability and obviously induced apoptosis under hypoxic conditions in vitro. Besides, the expression levels of caspase-3 and caspase-9 in hypoxic H9c2 were significantly increased after miR-184 inhibition.

Conclusions: Our findings indicate that inhibition of microRNA-184 may contribute to the development of cyanotic CHD via decreasing proliferation and inducing apoptosis of cardiomyocytes. Moreover, miR-184 inhibition may promote hypoxia-induced apoptosis via activation of caspase-3 and caspase-9. Congenital down-regulation of miR-184 may be a mechanism leading to CHD development.