Abstract 13003: MicroRNA-133 Promotes Direct Cardiac Reprogramming by Snai1 Repression and Silencing Fibroblast Signatures
Background: Cardiomyocytes are terminally differentiated cells and their regenerative capacity is limited. We recently succeeded in reprogramming of fibroblasts directly to functional cardiomyocytes by transduction of Gata4, Mef2c and Tbx5(GMT). However, the induction of fully reprogrammed functional cardiomyocytes is inefficient and roadblocks during reprogramming remain undefined. This study was designed to investigate the role of miRs in direct cardiac reprogramming.
Methods and Results: To determine if miRs induce cardiac reprogramming, we used mouse embryonic and neonatal tail-tip fibroblasts(MEF and TTF) from α-myosin heavy chain(αMHC)-GFP transgenic mouse in which only cardiomyocytes express GFP. We first transfected cardiac-enriched microRNAs(cardiac miRs) alone into αMHC-GFP MEF and TTF, but GFP or cardiac troponinT(cTnT) was not induced. Next, we transduced cardiac miRs plus GMT. Compared with control-miR, a pool of cardiac miRs greatly enhanced generation of αMHC-GFP+ cells. By screening of cardiac miRs, we identified miR-133 is sufficient for increasing cardiac induction. Addition of miR-133 increased generation of cTnT+ cells by 5 folds than control-miR. Whole transcriptome analyses demonstrated that miR-133 plus GMT (GMT/miR-133) changed global gene expression pattern of αMHC-GFP+ cells toward a cardiomyocyte-like state after 1 week of transduction. Moreover, spontaneous cellular contractions began after 10 days of GMT/miR-133 introduction, which generally took 4 weeks in GMT transduction. GMT/miR-133 increased the number of contracting cells nearly 10-fold. Molecularly, we found that the expression of Snai1, a master regulator of epithelial-to-mesenchymal transition, was a novel target of miR-133, and its expression was suppressed by miR-133 overexpression. Snai1 knockdown recapitulated miR-133-induced cardiac reprogramming, while Snai1 overexpression inhibited miR-133-induced reprogramming and activated fibroblastic signatures.
Conclusion: These results indicate thatmicroRNAs and transcription factors can cooperate in a powerful way toreprogram fibroblasts into functional cardiomyocytes. Importantly, this is the first study demonstrating the molecular mechanisms of direct reprogramming.
- © 2013 by American Heart Association, Inc.