SUMMARYThe interstitial and perivascular spaces of the heart contain stem-like cells including cardiac colony forming units -fibroblast (cCFU-F), a sub-fraction of PDGF-AB stimulated S + P + cell proliferation and conversion to myofibroblasts through a metabolic priming effect, yet significantly enhanced anatomical and functional repair via multiple cellular processes. Our study provides a rationale for a novel therapeutic approach to cardiac injury involving stimulating endogenous repair mechanisms via activation of cardiac stem and stromal cells.