Robust small molecule-aided cardiac reprogramming systems selective to cardiac fibroblasts

Direct cardiac reprogramming to induce cardiomyocyte-like cells, e.g., by GMT (Gata4, Mef2c and Tbx5), is a promising route for regenerating damaged heart in vivo and disease modeling in vitro. Supplementation with additional factors and chemical agents can enhance efficiency but raises concerns regarding selectivity to cardiac fibroblasts and complicates delivery for in situ cardiac reprogramming. Here, we screened 2000 chemicals with known biological activities and found that a combination of 2C (SB431542 and Baricitinib) significantly enhances cardiac reprogramming by GMT. Without Gata4, MT (Mef2c and Tbx5) plus 2C could selectively reprogram cardiac fibroblasts with enhanced efficiency, kinetics, and cardiomyocyte function. Moreover, 2C significantly enhanced cardiac reprogramming in human cardiac fibroblasts. 2C synergistically enhances cardiac reprogramming by inhibiting Alk5, Tyk2 and downregulating Oas2, Oas3, Serpina3n and Tgfbi. 2C enables selective and robust cardiac reprogram-ming that can greatly facilitate disease modeling in vitro and advance clinical therapeutic heart regeneration in vivo.