Abstract 247: Scaffold-stiffness Dependent Notch1 Activation Regulates Cardiogenic Gene Expression In Cardiac Progenitor Cells

Rationale: Cardiac progenitor cells (CPCs) are multipotent, self-renewing cells that can regenerate the myocardium and improve cardiac function in animal models of myocardial infarction (MI). However, limited survival of stem/progenitor cells inhibits cardiac regeneration. Force dependent Notch activation promotes cardiac development and cardiac gene expression in many adult stem cells. As dysregulation of Notch signaling leads to embryonic lethal cardiovascular defects, activating this critical pathway during cell transplantation could improve efficacy of stem cell therapy. Objective: Investigate i) whether self-assembling peptide scaffolds can be used to activate Notch1 signaling in CPCs to promote cardiogenic differentiation and ii) the effect of scaffold stiffness on Notch1 activation and differentiation. Methods: Rat CPCs (c-kit + ) were cultured for 48h in 3D self-assembling scaffolds of varying stiffness (1% low, 2% high): empty scaffolds (RADA), scaffolds modified with peptide mimicking Notch1 ligand, Jagged1 (RJAG), or scaffolds modified with a scrambled peptide (RSCR) and cardiogenic gene expression measured by qRT-PCR. CHO cells expressing Notch1 responsive YFP were also cultured in the above scaffolds for 48h and YFP expression was determined. Results are mean ± SEM with p<0.05 considered significant by one or two-way ANOVA with appropriate post test. Results: In the Notch1 reporter cells, Notch1 activation increased significantly in presence of RJAG (p<0.01) and on increasing scaffold stiffness (p<0.01,n=6) indicating scaffold stiffness-dependent Notch1 activation. Culture of CPCs in RJAG containing 1% scaffolds (low stiffness) significantly increased early endothelial and smooth muscle but not cardiac gene expression while in 2% scaffolds (high stiffness) significantly increased only cardiac and not endothelial or smooth muscle gene expression (p<0.05, n≥4). Conclusions: Taken together, these data show that i) Notch1 activation in 3D is dependent on ligand density and scaffold stiffness and ii) stiffness dependent Notch1 activation differentially regulates cardiogenic gene expression in CPCs. Therefore, delivery of CPCs in JAG containing scaffolds could be used to improve cardiac function following MI.