Young Adult Bone Marrow–Derived Endothelial Precursor Cells Restore Aging-Impaired Cardiac Angiogenic Function

Delivery of young bone marrow–derived stem cells offers a novel approach for restoring the impaired senescent cardiac angiogenic function that may underlie the increased morbidity and mortality associated with ischemic heart disease in older individuals. Recently, we reported that alterations in endothelial cells of the aging heart lead to a dysregulation in the cardiac myocyte platelet-derived growth factor (PDGF)-B–induced paracrine pathway, which contributes to impaired cardiac angiogenic function. Based on these results, we hypothesized that cellular restoration of the PDGF pathway by bone marrow–derived endothelial precursor cells (EPCs) could reverse the aging-associated decline in angiogenic activity. In vitro studies revealed that young murine (3-month-old) bone marrow–derived EPCs recapitulated the cardiac myocyte–induced expression of PDGF-B, whereas EPCs from the bone marrow of aging mice (18-month-old) did not express PDGF-B when cultured in the presence of cardiac myocytes. Transplantation of young, but not old, genetically marked syngeneic bone marrow cells into intact, unirradiated aging mice that populated the endogenous senescent murine bone marrow incorporated into the neovasculature of subsequently transplanted syngeneic neonatal myocardium. Moreover, the young bone marrow–derived EPCs restored the senescent host angiogenic PDGF-B induction pathway and cardiac angiogenesis, with graft survival and myocardial activity in the aging murine host (cardiac allograft viability3-month-old controls, 8/8; 18-month-old controls, 1/8; 18-month-old donors receiving bone marrow from 3-month-old mice, 15/16; or 18-month-old mice, 0/6;P