FGF4 and ascorbic acid enhance the maturation of induced cardiomyocytes by activating JAK2–STAT3 signaling

Direct cardiac reprogramming represents a novel therapeutic strategy to convert non-cardiac cells such as fibroblasts into cardiomyocytes (CMs). This process involves essential transcription factors, such as Mef2c, Gata4, Tbx5 (MGT), MESP1, and MYOCD (MGTMM). However, the small molecules responsible for inducing immature induced CMs (iCMs) and the signaling mechanisms driving their maturation remain elusive. Our study explored the effects of various small molecules on iCM induction and discovered that the combination of FGF4 and ascorbic acid (FA) enhances CM markers, exhibits organized sarcomere and T-tubule structures, and improves cardiac function. Transcriptome analysis emphasized the importance of ECM-integrin-focal adhesions and the upregulation of the JAK2–STAT3 and TGFB signaling pathways in FA-treated iCMs. Notably, JAK2–STAT3 knockdown affected TGFB signaling and the ECM and downregulated mature CM markers in FA-treated iCMs. Our findings underscore the critical role of the JAK2–STAT3 signaling pathway in activating TGFB signaling and ECM synthesis in directly reprogrammed CMs. Cardiovascular diseases are a major global cause of death, often due to the loss of cardiomyocytes and increased heart scarring. Existing treatments, like medication and heart transplants, have limitations, emphasizing the need for new cell regeneration therapies. This study investigates direct cardiac reprogramming—a new method to regenerate heart muscle cells by transforming fibroblasts into induced cardiomyocytes using specific factors and small molecules. The team tested various small molecules and found that a mix of FGF4 and ascorbic acid significantly improves the maturation of iCMs. They used techniques like immunofluorescence staining, flow cytometry, and electrophysiological analysis to evaluate the conversion and maturation of iCMs. This study shows that direct cardiac reprogramming can be enhanced with the right combination of small molecules, providing a promising strategy for heart regeneration. This summary was initially drafted using artificial intelligence, then revised and fact-checked by the author.