Human peripheral blood-derived CD31⁺ cells have robust angiogenic and vasculogenic properties and are effective for treating ischemic vascular disease

Objectives: This study aimed to determine if CD31 is a novel marker of a circulating angio-vasculogenic cell population and to establish the cells' therapeutic effects on experimental ischemia. Background: Emerging evidence suggested that therapeutic mechanisms underlying various bone marrow-derived cells are due to paracrine effects. Furthermore, the vasculogenic potential of these cells is under debate. CD31 is a well-known marker for endothelial cells but is also expressed in a fraction of peripheral blood (PB) mononuclear cells. Methods: CD31⁺ cells were isolated from human PB by magnetic-activated cell sorting. The gene expression profile was examined by deoxyribonucleic acid microarray and real-time reverse transcriptase polymerase chain reaction. Various in vitro endothelial differentiation or vasculogenic assays were conducted. Finally, cells were directly implanted into a mouse hind limb ischemia model to test angiogenic-vasculogenic and therapeutic effects. Results: Fluorescent-activated cell sorter analysis revealed that PB-CD31 ⁺ cells exhibited endothelial and hematopoietic stem/progenitor markers. CD31⁺ cells had higher levels of expression of proangiogenic genes on microarray and real-time reverse transcriptase polymerase chain reaction and generated higher numbers of endothelial progenitor cells than CD31^- cells did. CD31⁺ cells spontaneously formed vascular tubelike structures and exhibited an endothelial cell phenotype in vitro. In a hind limb ischemia model, CD31⁺ cell transplantation augmented blood perfusion and prevented limb loss. Both angiogenic cytokines and capillary density were increased, suggesting CD31⁺ cells augmented neovascularization. Conclusions: CD31 is a novel marker that designates circulating angiogenic and vasculogenic cells. These cells are easily isolated from human PB and thus are a novel candidate for treatment of ischemic cardiovascular disease.