Inhibition of profibrotic signalling enhances the 5-azacytidine-induced reprogramming of fibroblasts into cardiomyocytes

•Improving the conversion efficiency of CFs to cardiac myocytes is a challenging task.•The appearance of fibrotic prevents cardiac reprogramming.•Inhibition of pro-fibrotic signalling by the TGF-β receptor inhibitor enhances the reprogramming of CFs to iCMs. Recent studies have shown that cardiac fibroblasts (CFs) can be transformed into induced cardiomyocytes (iCMs). This phenomenon represents a potential method for rescuing damaged myocardia after myocardial infarction. The mechanism underlying cardiac reprogramming regulation must be clarified to improve the induction efficiency of iCMs. In this study, we treated CFs with 5-aza for 24 h and added TGF-β inhibitor A83-01 for 2 weeks in vitro to investigate the effect of inhibiting fibrosis on myocardial differentiation. Inhibition of TGF-β1 activity with A83-01 significantly decreased the expressions of collagen III and α-SMA and increased the expression of myocardial specific marker cTnT and gap junction protein Cx43 in CFs, enhanced cardiac reprogramming as opposed to 2 weeks with 5-aza alone. Transcriptome and quantitative real-time reverse transcription-polymerase chain reaction analysis at the 14th day postinduction of A83-01 revealed that the expression of genes involved in cardiac development increased in the presence of 5-aza. These findings suggest that the addition of A83-01 remarkably inhibits profibrotic signalling and improved the efficiency of iCMs, provide new insights into the molecular mechanisms of cardiac reprogramming and promote the use of iCMs in clinical applications.