Abstract 11415: Enhancing Direct Cardiac Reprogramming Efficiency Using Small Molecules
The ability to directly trans-differentiate fibroblasts into cardiomyocytes through overexpression of three core transcription factors, Gata4, Mef2C &TBX5 (GMT), has been demonstrated by our group and others. Direct cardiac reprogramming has great potential to treat heart failure. However, clinical application remains limited due to inefficiencies in the reprogramming process and immaturity of the differentiated cardiomyocytes. In the current work, using a chemical approach we aim to increase the efficiency and the maturation of these directly reprogrammed cardiomyocytes.
We have optimized a high-throughput screening method in 384-well plates using an alpha-MHC-GFP reporter to detect cardiac reprogramming in mouse cardiac fibroblasts. We screened 5500 compounds and identified 20 hits which have increased the reprogramming efficiency by 2-6 fold compared to controls. Among these top hits, 4 TGF-β inhibitors (DS 1-4) and 4 WNT inhibitors (DS 5-8) enhanced direct cardiac reprogramming. Further in depth investigations showed that the combination of the TGF-β inhibitor DS1 and the WNT inhibitor DS5 increased reprogramming efficiency 7 fold when added to the GMT-overexpressing fibroblasts on the first day of reprogramming. This combination of small molecules also enhanced the maturation of the reprogrammed cells, as we observed beating cells after only 1 week of reprogramming compared to 6–8 weeks without the small molecules. Activation of canonical WNT signaling or TGF-β signaling significantly abrogates the improvement in cardiac reprogramming by DS1 and DS5. These results indicate the specificity of the action of these inhibitors through the canonical WNT and TGF-β pathways. In a translational effort, we injected DS1, 2 and 5 intraperitoneally in mice for 2 weeks in combination with GMT following myocardial infarction (MI) and found a significant improvement in cardiac function as represented by an ejection fraction of 39.11% ±1.2% in the GMT + compounds group vs. 28.44% ± 3.98% in the GMT only group (p<0.05), 6 weeks after MI compared to an ejection fraction of 22.72% in the control untreated group.
In conclusion, small molecules, especially the TGF-β inhibitors and WNT inhibitors, greatly enhanced direct reprogramming in vitro and in vivo.
Author Disclosures: T.M. Mohamed: None. N. Stone: None. E. Berry: None. H. Wang: None. S. Ding: None. D. Srivastava: None.
- © 2015 by American Heart Association, Inc.