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In Vivo Stimulatory Effect of Endothelial Progenitor Cells on Vasodilator Function of Rabbit Cerebral Arteries

Evidence continues to accumulate on the importance of endothelial progenitor cells (EPCs) in neovascularization of ischemic tissues and repair of injured endothelium. The present study was designed to determine the in vivo effect of EPCs on the vasomotor function of rabbit cerebral arteries. Isolated mononuclear cells from rabbit peripheral blood were cultured in endothelial growth medium (EGM‐2) for 7 days, yielding EPCs. Rabbits were injected intracisternally with either autologous EPCs (1x105 to 5x105 cells) or vehicle (EGM‐2) as control. After 24 hours, basilar arteries were isolated, vasomotor function was studied in organ chambers, and protein expression in the basilar arteries quantified by Western blot analysis. In rabbits treated with EPCs, contractions to either potassium chloride (80 mmol/L) or histamine (10−9 to 10−5 mol/L) were not affected. However, endothelium‐dependent relaxations to acetylcholine (10−9 to 10−5 mol/L) and endothelium‐independent relaxations to a NO donor, DEA‐NONOate (10−9 to 10−5 mol/L) were enhanced in basilar arteries from EPC‐treated rabbits. Western blot studies demonstrated increased expressions of cyclooxygenase‐2 and prostacyclin synthase (PGI2 synthase) only in arteries exposed to EPCs. Results of the present study suggest that in vivo administration of EPCs could augment vasodilatation of the cerebral arteries by increasing vascular production of prostacyclin.