Abstract 15007: Chemical Enhancement of Direct Cardiac Reprogramming in vitro and in vivo
Reprogramming of cardiac fibroblasts into induced cardiomyocyte-like cells (iCMs) in situ represents a promising strategy for cardiac regeneration. A combination of three cardiac transcription factors, Gata4, Mef2c and Tbx5 (GMT), can convert fibroblasts into iCMs, albeit with low efficiency in vitro. Here, we screened 5,500 compounds in primary mouse cardiac fibroblasts and identified 19 compounds that increased reprogramming efficiency by 2-6 fold compared to controls. Among these were 4 chemicals annotated as TGF-β inhibitors and 4 as WNT inhibitors. Activation of TGF-β signaling or canonical WNT signaling abrogated the improvement in cardiac reprogramming by either class of chemical inhibitors, respectively. The combination of a transforming growth factor (TGF)-β inhibitor and a WNT inhibitor increased reprogramming efficiency eight-fold when added to GMT-overexpressing cardiac fibroblasts. The small-molecules also enhanced the speed and the quality of cell conversion, as we observed beating cells as early as 1 week after reprogramming compared to 6-8 weeks with GMT alone. In vivo, mice exposed to GMT plus TGF-β and WNT inhibition for 2 weeks after myocardial infarction (MI) showed significantly improved reprogramming and cardiac function compared to those exposed to only GMT. 12 weeks after MI, ejection fraction by MRI measured as follows: GMT + compounds: 38.74% ±1.39%; compounds only: 22.72±3.78%; GMT only: 28.49±3.08%; DMSO only 21.36±3.37% (p<0.05 for GMT compared to DMSO and for GMT + compounds compared to GMT only, n=6-7 in each group). Human cardiac reprogramming was similarly enhanced and accelerated upon TGF-β and WNT inhibition and was achieved most efficiently with GMT plus Myocardin. Thus, TGF-β and WNT inhibitors jointly enhance GMT-induced direct cardiac reprogramming from cardiac fibroblasts in vitro and in vivo and provide a more robust platform for cardiac regeneration.
Author Disclosures: T.M. Mohamed: None. N. Stone: None. E. Berry: None. E. Radzinsky: None. Y. Huang: None. K. Pratt: None. Y. Ang: None. P. Yu: None. H. Wang: None. S. Tang: None. S. Magnitsky: None. S. Ding: None. K. Ivey: None. D. Srivastava: None.
- © 2016 by American Heart Association, Inc.