Abstract 21: Stiffness-Dependent Notch1 Activation Regulates Cardiogenic Differentiation of Cardiac Progenitor Cells
Cardiac progenitor cells (CPCs) are multipotent, self-renewing cells that can regenerate the myocardium and improve cardiac function in animal models of MI by cardiogenic differentiation. However, limited survival of stem/progenitor cells, myocardial scarring and fibrosis inhibit cardiac regeneration. Notch signaling promotes early cardiac development, cardiomyocyte survival and cardiac gene expression in circulating endothelial progenitor cells, mesenchymal stem cells and CPCs. As misregulation of Notch signaling during development is lethal due to cardiovascular defects, activating this critical pathway during cell transplantation could improve the efficacy of stem cell therapy. We investigated whether self-assembling peptide nanofiber hydrogels can be used to activate Notch1 signaling.
The 16 amino acid self-assembling scaffold (RAD) was modified with a 20 amino acid peptide mimicking the active site of Notch1 ligand, Jagged1 (RJAG) or with the corresponding scrambled peptide (RSCR). To determine whether scaffold stiffness regulates Notch1 activation, CHO cells with Notch1 responsive YFP expression were cultured in scaffolds of 1-3% w/v in presence of RSCR or RJAG at a 1:10 ligand: scaffold ratio in 3D. Presence of the RJAG peptide (p<0.01) and % concentration of the scaffold (p<0.01) increased Notch1 activation significantly (n=5) indicating that RJAG mediated Notch1 activation in 3D is scaffold stiffness-dependent. Therefore, CPCs were cultured within 3D scaffolds (1-3% w/v; empty, scaffold +RJAG or RSCR) and cardiogenic gene expression was determined by qPCR. An increase in expression of early endothelial (Flk1, Flt1, vWF) and smooth muscle (sm22α, sm αactin) genes was observed in CPCs cultured in 3D scaffolds containing RJAG but not when cultured in 2D. These data show that Notch1 activation is dependent on ligand density and scaffold stiffness. Delivery of CPCs in JAG1 containing self-assembling scaffolds could be used to enhance therapeutic angiogenesis and improve cardiac function following myocardial infarction.
- © 2012 by American Heart Association, Inc.