β2-Adrenergic Receptor Stimulation Improves Endothelial Progenitor Cell–Mediated Ischemic Neoangiogenesis

Rationale:Endothelial progenitor cells (EPCs) are present in the systemic circulation and home to sites of ischemic injury where they promote neoangiogenesis. β2-Adrenergic receptor (β2AR) plays a critical role in vascular tone regulation and neoangiogenesis. Objective:We aimed to evaluate the role of β2AR on EPCs’ function. Methods and Results:We firstly performed in vitro analysis showing the expression of β2AR on EPCs. Stimulation of wild-type EPCs with β-agonist isoproterenol induced a significant increase of Flk-1 expression on EPCs as assessed by fluorescence-activated cell sorter. Moreover, β2AR stimulation induced a significant increase of cell proliferation, improved the EPCs migratory activity, and enhanced the EPCs’ ability to promote endothelial cell network formation in vitro. Then, we performed in vivo studies in animals model of hindlimb ischemia. Consistent with our in vitro results, in vivo EPCs’ treatment resulted in an improvement of impaired angiogenic phenotype in β2AR KO mice after i...