Circulating CD34‐positive cells stimulate phosphorylation of endothelial nitric oxide synthase in cerebral arteries

Abstract

In animal models, transplantation of CD34+cells has beneficial effect on cerebral ischemia and recovery from stroke, however, the mechanism underlying cerebrovascular effects of CD34+cells is poorly understood. In the present study, CD34+ cells were obtained by magnetic cell sorting of rabbit peripheral blood mononuclear cells. Rabbit basilar arteries were exposed to autologous CD34+ cells (~5×105 cells) in vitro or in vivo. Arteries treated with endothelial growth medium‐2 (EGM‐2, vehicle) served as controls. Twenty four hours after intracisternal delivery of cells, basilar arteries were isolated and studied. In arteries treated with CD34+ cells either in vivo or in vitro, protein expression of phosphorylated Ser‐473‐Akt and phosphorylated Ser‐1177 endothelial nitric oxide synthase (eNOS) were significantly increased (n = 6, P<0.05), while expressions of eNOS, Akt, inducible NOS, cyclooxygenase‐1 (COX‐1) and COX‐2 were not affected (n = 6, P>0.05). In arteries exposed to CD34+ cells in vitro, cGMP content was significantly augmented (n = 4, P<0.01), whereas cAMP levels remained unaffected (n = 4, P>0.05). Our results suggest that in basilar artery, CD34+ cells stimulate phosphorylation of Akt and eNOS thereby increasing endothelial NO production. These findings may help to explain described therapeutic effect of transplanted CD34+ cells in cerebral circulation.