Chemical Enhancement of In Vitro and In Vivo Direct Cardiac Reprogramming
Background—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.
Methods—We screened 5,500 compounds in primary cardiac fibroblasts to identify the pathways that can be modulated to enhance cardiomyocyte reprogramming.
Results—We found that a combination of the transforming growth factor (TGF)-β inhibitor SB431542 and the WNT inhibitor XAV939 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, SB431542, and XAV939 for 2 weeks after myocardial infarction showed significantly improved reprogramming and cardiac function compared to those exposed to only GMT. Human cardiac reprogramming was similarly enhanced upon TGF-β and WNT inhibition and was achieved most efficiently with GMT plus Myocardin.
Conclusions—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.
- Received July 26, 2016.
- Revision received September 14, 2016.
- Accepted October 21, 2016.