Background: Endothelial progenitor cells (EPCs) induce neovascularization and repair vascular damage. We have demonstrated that EPC function is impaired in hypertensive rats with increases in oxidative stress and that angiotensin II receptor blockers improved the impaired function of EPCs. In this study, we investigated basal EPC functions in normotensive control subjects and patients with essential hypertension and the effect of losartan on EPC function in hypertensive patients.

Methods: Eighteen normotensive control subjects and 36 patients with essential hypertension who were undergoing treatment participated in the study. Hypertensive patients were randomly selected to receive 50mg of losartan or 4 mg of trichlormethiazide daily for 4 weeks. Peripheral blood mononuclear cells were isolated and cultured to assay EPC colony formation. Blood pressure, biological examination, and oxidative stress were evaluated in all subjects.

Results: The number of EPC colonies was significantly lower in patients with essential hypertension than in normotensive control subjects. EPC colony number was significantly and inversely correlated with systolic and diastolic blood pressure in all subjects. EPC colony number was significantly increased by treatment with losartan in patients with essential hypertension but not affected by treatment with trichlormethiazide.

Conclusions: EPC function was inversely correlated with blood pressure and was impaired in essential hypertension. Losartan significantly improved the impaired EPC function in hypertensive patients. Impaired EPC function may determine the cardiovascular complications in essential hypertension. The improvement of EPC function with the administration of angiotensin II receptor blockers is considered to be one of the cardiovascular protective effects.