MicroRNA profiling during rat ventricular maturation: A role for miR-29a in regulating cardiomyocyte cell cycle re-entry.

Recent studies demonstrated that the mammalian heart possesses some capacity to proliferate. We observed cardiomyocyte proliferation within 4 weeks of age (P4W) in rats. We found 95 microRNAs that are differentially expressed in P4W cardiomyocytes. MicroRNA-29a was among the most highly up-regulated microRNAs in P4W cardiomyocytes. Overexpression of microRNA-29a suppressed the proliferation of H9c2 cell line. MicroRNA-29a inhibition induced cardiomyocytes to proliferate, accelerated the G1/S and G2/M transition, and up-regulated the cell cycle gene expression. Cyclin D2 (CCND2) was identified as a direct target of microRNA-29a. These findings indicate that microRNA-29a is involved in cardiomyocyte proliferation during postnatal development.