Abstract 17539: IGF promotes Cardiac Lineage Induction by Selective Expansion of Mesoderm in vitro
Purpose: A thorough understanding of the developmental processes that direct embryonic stem cells (ESCs) towards a cardiac fate is essential for translational application of ESCs in cardiac disease modeling and therapy.
Methods: This study set out to identify, by high throughput screening, key signaling pathways that regulate early cardiac lineage formation.
Results: A panel of 44 signaling molecules was tested for ability to induction of Nkx2.5+ cardiac progenitor cell (CPC) formation during ESC in vitro differentiation. Consistent with previous reports, treatment with insulin-like growth factor (IGF) family of ligands (e.g. IGF1, IGF2, insulin) resulted in expansion of Nkx2.5+ CPCs by 7.4-fold ± 0.79 (IGF1; 2.71%±0.27 vs. 0.37%±0.03); 6.3-fold ± 0.46 (IGF2; 2.96%±0.25 vs. 0.47%±0.07) and 6.3-fold ± 0.35 (insulin; 2.85%±0.01 vs. 0.45%±0.03), respectively. To examine the mechanism of IGF-mediated cardiac lineage expansion, we quantified the abundance of endoderm, ectoderm, and mesoderm populations after IGF treatment and found that IGF increased the number of mesendodermal cells (Brachyury+ cell population: IGF1 treated; 14.3%±1.51, IGF2 treated; 19.3%±0.95, and insulin treated 17.3%±1.51 compared with control; 3.95%±0.56), but not of ectodermal (Nestin+) populations. This was corroborated by analysis of lineage marker expression using quantitative PCR. Mechanistically, IGF treatment selectively enhanced the proliferation of Brachyury+ cells (Brachyury+/Ki-67+ cells = 46.2%±7.27, 46.0%±12.7, and 50.3%±8.58 after IGF1, IGF2, or insulin supplementation vs. 26.0%±8.34 in control). Furthermore, IGFs appear to directly signal to mesodermal cells through phosphorylation of the Akt/mTOR pathway.
Conclusions: Our data uncover a novel role for IGF family ligands to regulate cardiac lineage induction through its ability to expand the mesodermal cell population. These findings contribute to our understanding of early developmental events during germ layer induction and provide new approaches to enhance in vitro cardiogenesis for regenerative medicine applications.
- © 2013 by American Heart Association, Inc.