A cardiac fibrosis determinative factor, Meox1, blocks direct reprogramming of cardiac myofibroblasts to cardiomyocyte-like cells

Abstract Direct reprogramming of cardiac fibroblasts (CFs) into induced cardiomyocyte-like cells (iCMs) is a promising regenerative medicine therapy for myocardial infarction (MI) patients. CFs are activated and transition to myofibroblasts (MFs) after MI, which are abundant in the injured area. However, MFs show lower cardiac reprogramming efficiency. We identified Meox1 , a TGF-β1 downstream transcription factor, which involved in cardiac fibrosis, as a barrier to cardiac reprogramming. In MFs induced with MGT (Mef2c, Gata4 and Tbx5) or MGT plus Myocd (MGTM), Meox1 knockdown results in significant increase in reprogramming efficiency. RNA-seq and CHIP-seq analysis showed the function of Meox1 in stabilizing a fibrosis-associated transcriptomic program. Furthermore, mutations disrupting the MEOX1 DNA binding domain or fusing it to a transcriptional repressor domain attenuate its inhibition of cardiac reprogramming. Dual recombinase tracing showed that iCM reprogramming efficiency is higher and cardiac function can be restored after MI with Meox1 knockdown. Finally, we found that Meox1 knockdown improved reprogramming efficiency in human CFs. These findings provide a potent target that can be further developed for direct cardiac regeneration.