Akt1/Protein Kinase B Enhances Transcriptional Reprogramming of Fibroblasts to Functional Cardiomyocytes

Conversion of fibroblasts to functional cardiomyocytes represents a potential approach for restoring cardiac function following myocardial injury, but the technique thus far has been slow and inefficient. To improve the efficiency of reprogramming fibroblasts to cardiac-like myocytes (iCMs) by cardiac transcription factors (Gata4, Hand2, Mef2c, and Tbx5=GHMT), we screened 192 protein kinases and discovered that Akt/protein kinase B dramatically accelerates and amplifies this process. Approximately 50% of reprogrammed fibroblasts displayed spontaneous beating after three weeks of induction by Akt plus GHMT. Furthermore, addition of Akt1 to GHMT evoked a more mature cardiac phenotype for iCMs, as seen by enhanced polynucleation, cellular hypertrophy, gene expression, and metabolic reprogramming. Igf1 and Pi3 kinase acted upstream of Akt, whereas mTORC1 and Foxo3a acted downstream of Akt to influence fibroblast-to-cardiomyocyte reprogramming. These findings provide new insights into the molecular basis of cardiac reprogramming and represent an important step toward further application of this technique. We performed RNA-Seq using either isolated adult mouse ventricular cardiomyocytes (CMs) or MEFs treated for three weeks with empty vector, GHMT (iCMs cell sorted using αMHC-GFP before RNA-Seq), or AGHMT (iCMs cell sorted using αMHC-GFP before RNA-Seq).