Overexpression of the β2AR gene improves function and re-endothelialization capacity of EPCs after arterial injury in nude mice

Background Proliferation and migration of endothelial progenitor cells (EPCs) play important roles in restoring vascular injuries. β2 adrenergic receptors (β2ARs) are widely expressed in many tissues and have a beneficial impact on EPCs regulating neoangiogenesis. The aim of the present study was to determine the effect of overexpressing β2ARs in infused peripheral blood (PB)-derived EPCs on the re-endothelialization in injured vessels. Methods Induction of endothelial injury was performed in male nude mice that were subjected to wire-mediated injury to the carotid artery. Human PB-derived EPCs were transfected with an adenovirus serotype 5 vector expressing β2AR (Ad5/β2AR-EPCs) and were examined 48 h later. β2AR gene expression in EPCs was detected by real-time polymerase chain reaction and Western blot analysis. In vitro, the proliferation, migration, adhesion, and nitric oxide production of Ad5/β2AR-EPCs were measured. Meanwhile, phosphorylated Akt and endothelial nitric oxide synthase (eNOS), which are downstream of β2AR signaling, were also elevated. In an in vivo study, CM-DiI-labeled EPCs were injected intravenously into mice subjected to carotid injury. After 3 days, cells recruited to the injury sites were detected by fluorescent microscopy, and the re-endothelialization was assessed by Evans blue dye. Results In vitro, β2AR overexpression augmented EPC proliferation, migration, and nitric oxide production and enhanced EPC adhesion to endothelial cell monolayers. In vivo, when cell tracking was used, the number of recruited CM-DiI-labeled EPCs was significantly higher in the injured zone in mice transfused with Ad5/β2AR-EPCs compared with non-transfected EPCs. The degree of re-endothelialization was also higher in the mice transfused with Ad5/β2AR-EPCs compared with non-transfected EPCs. We also found that the phosphorylation of Akt and eNOS was increased in Ad5/β2AR-EPCs. Preincubation with β2AR inhibitor (ICI118,551), Akt inhibitor (ly294002), or eNOS inhibitor (L-NAME) significantly attenuated the enhanced in vitro function and in vivo re-endothelialization capacity of EPCs induced by β2AR overexpression. Conclusions The present study demonstrates that β2AR overexpression enhances EPC functions in vitro and enhances the vascular repair abilities of EPCs in vivo via the β2AR/Akt/eNOS pathway. Upregulation of β2AR gene expression through gene transfer may be a novel therapeutic target for endothelial repair.