In Vitro Conversion of Murine Fibroblasts into Cardiomyocyte-Like Cells

Direct reprogramming of fibroblasts into induced cardiomyocytes (iCMs) holds great promise as a potential treatment for cardiovascular disease, many of which are associated with tremendous loss of functional cardiomyocytes and simultaneous formation of scar tissue. Burgeoning studies have shown that the introduction of three minimal transcriptional factors, Gata4, Mef2c, and Tbx5 (G/M/T), could convert murine fibroblasts into iCMs that closely resemble endogenous CMs both in vitro and in vivo. Recent studies on iCM cell fate determination have demonstrated that the removal of genetic and epigenetic barriers could facilitate iCM reprogramming. However, varied reprogramming efficiency among research groups hinders its further study and potential applicability. Here, we provide a newly updated and detailed protocol for in vitro generation and evaluation of functional iCMs from mouse embryonic fibroblasts and neonatal cardiac fibroblasts using retroviral polycistronic construct encoding optimal expression of G/M/T factors. We hope that this optimized protocol will lay the foundation for future mechanistic studies of murine iCMs and further improvement of iCM generation.