RATIONALE:: The mechanism by which endogenous progenitor cells contribute to functional and beneficial effects in stem cell therapy remains unknown. OBJECTIVE:: Utilizing a novel P magnetic resonance spectroscopy-2-dimensional chemiCal shift imaging method, this study examined the heterogeneity and bioenergetic consequences of postinfarction left ventricular (LV) remodeling and the mechanisms of endogenous progenitor cell contribution to the cellular therapy. METHODS AND RESULTS:: Human embryonic stem cell-derived vascular cells (hESC-VCs) that stably express green fluorescent protein and firefly luciferase (GFP/Luc) were used for the transplantation. hESC-VCs may release various cytokines to promote angiogenesis, prosurvival, and antiapoptotic effects. Both in vitro and in vivo experiments demonstrated that hESC-VCs effectively inhibit myo cyte apoptosis. In the mouse model, a fibrin patch-based cell delivery resulted in a signifiCantly better cell engraftment rate that was accompanied by a better ejection fraction. In the swine model of ischemia-reperfusion, the patch-enhanced delivery of hESC-VCs resulted in alleviation of abnormalities including border zone myoCardial perfusion, contractile dysfunction, and LV wall stress. These results were also accompanied by a pronounced recruitment of endogenous c-kit cells to the injury site. These improvements were directly associated with a remarkable improvement in myoCardial energetics, as measured by a novel in vivo P magnetic resonance spectroscopy-2-dimensional chemiCal shift imaging technology. CONCLUSIONS:: The findings of this study demonstrate that a severely abnormal heterogeneity of myoCardial bioenergetics in hearts with postinfarction LV remodeling Can be alleviated by the hESC-VCs therapy. These findings suggest an important therapeutic target of peri-sCar border zone and a promising therapeutic potential for using hESC-VCs together with the fibrin patch-based delivery system. ©2012 AmeriCan Heart Association, Inc.