Circulating endothelial progenitor cells are reduced in hemodialysis patients

Objective: The risk of cardiovascular disease in hemodialysis patients is far greater than in the general population. Endothelial progenitor cells (EPCs) circulating in the peripheral blood contribute to neovascularization in the ischemic tissue. EPCs are considered to be included in CD34 positive (CD34(+)) or AC133 positive (AC133(+)) mononuclear cells (MNCs). This study's aim was to determine the number and functional activity of EPCs in hemodialysis patients and age-matched control subjects. Methods: The numbers of CD34(+) MNCs and AC133(+) MNCs in the peripheral blood were quantified by flow cytometry. The peripheral blood EPCs were also examined by an in vitro culture assay. The levels of serum vascular endothelial growth factor (VEGF) were measured by sandwich enzyme immunoassay. Results: The numbers of CD34(+) MNCs and AC133(+) MNCs were significantly reduced by 56% and 49%, respectively, in hemodialysis patients (n = 50) compared with control subjects (n = 36). The number of EPCs determined by the culture assay was also significantly reduced by 41% in hemodialysis patients compared with control subjects. Multivariate analysis revealed that none of the atherosclerotic risk factors were independent predictors of reduced CD34(+) MNC counts. The serum VEGF levels in hemodialysis patients were not different from those in control subjects and did not correlate with CD34(+) MNC counts. Conclusion: Circulating EPCs are significantly reduced in hemodialysis patients, which might be related to impaired neovascularization and cardiovascular disease in these patients.