Abstract 35: Enhanced Reprogramming of Human Fibroblasts into Cardiomyocytes Using Minimal Transcription Factors

Abstract

The adult human heart has limited regenerative capacity and is thus an important target for novel regenerative approaches to replenish lost cardiomyocytes after cardiac injury. Cardiac reprogramming that converts fibroblasts to contractile induced cardiomyocytes (iCMs) by overexpressing cardiac lineage specific transcription factors holds great promise as an alternative approach for cardiac regeneration and disease modeling. Significant advance has been made to generate mouse iCMs; however, human iCM (hiCM) generation remains challenging and the yield is low for clinical applications. Here, we leveraged the knowledge that we learned from studying mouse iCM reprogramming to define the optimal condition for hiCM induction. We titrated the dosage of the human reprogramming factors systematically and surprisingly found the minimal core components GATA4, MEF2C and TBX5 were sufficient to induce cardiac fate in human primary fibroblasts. This is in sharp contrast to what has been reported in the literature. Subsequently, we cloned these three factors into a polycistronic vector separated by 2A peptides for defined ratio of protein expression. By optimizing the growth condition, we further improved the efficiency of hiCM reprogramming. Mechanistically, we found the balanced expression of this minimal combination of transcription factors with tailored microenvironment enhanced the establishment of cardiac program in non-myocytes. In sum, our study demonstrates that the use of a single vector with only three transcription factors simplifies generation and improves the yield of hiCMs for potential future clinical applications.