Abstract 14016: Secreted Frizzled Related Protein 2 (Sfrp2) Regulates Resident Cardiac Progenitor Cell Proliferation and Differentiation by Modulating Wnt6 Canonical Signaling
Introduction: Endogenous repair via activation of cardiac progenitor cells represents an attractive therapeutic approach for limiting remodeling and enhancing cardiac regeneration post infarction. Previously, we have shown that Sfrp2, a Wnt pathway inhibitor, induces cell cycle arrest and enhances cardiac differentiation in CPCs in vitro. Here, we identify Wnt6 as a candidate for modulating Sfrp2 canonical Wnt pathway inhibition, activation cell cycle and cardiac morphogenic transcriptional signatures. Moreover we explore the role of Sfrp2 in cardiac regeneration in vivo.
Methods: Isolated mCPCs were treated with recombinant Sfrp2 protein at 1-100 nM. Differentiation was documented by NKX2.5 staining. Gene expression profiling was completed using Affymetrix Mouse Gene 2.0 ST array. Wnt-Sfrp2 interactions were identified by CoIP. The GSK3β inhibitor BIO, JNK inhibitor SP600125 or CaMKII inhibitor KN-93 was used to test the functional importance of Wnt pathways. The effect of Sfrp2 in vivo was evaluated by direct injection of 0.5µg of Sfrp2 protein in a mouse model of ischemia/reperfusion (I/R) injury.
Results: Treatment of mCPCs with Sfrp2 in the presence of canonical Wnt inhibitor BIO but not SP600125 or KN-93 inhibited the Sfrp2 induced differentiation. Accordingly, Sfrp2 inhibited the canonical/β-Catenin pathway but did not significantly affect non-canonical Wnt signaling. Expression and CoIP analysis revealed that Sfrp2 binds Wnt6, a canonical Wnt modulator shown to restrict cardiac muscle differentiation. Downstream targets as revealed by microarray analysis included multiple genes involved in cell cycle regulation (Cyclin D1, Cdk4 and Myc) and cardiac morphogenesis (Id1, Id3, Jag1, Hdac4, Bmp2 and Bmp2r). In vivo, Sfrp2 reduced infarct size when given 2 days post I/R injury and increased the number of new small cTnT+ cardiomyocytes in the infarct border zone.
Conclusions: Sfrp2 modulates the proliferative and commitment stage of mCPC in vitro by inhibition of canonical Wnt6 signaling. This inhibition removes mCPC from the cell cycle and allows for their priming which drives expression of the cardiac marker Nkx2.5 and subsequent differentiation. Accordingly, in vivo administration of Sfrp2 resulted in enhanced cardiac regeneration.
- © 2011 by American Heart Association, Inc.