VDR Expression on Circulating Endothelial Progenitor Cells in Dialysis Patients Is Modulated by 25(OH)D Serum Levels and Calcitriol Therapy

Background/Aims: Vitamin D deficiency is associated with endothelial dysfunction in uremic patients, possibly by the impairment in the number and function of endothelial progenitor cells (EPCs). In 89 hemodialysis patients, we investigated the factors associated with the number of circulating EPCs (CD34(+)/CD133(+)/KDR(+) and CD34(+)/CD133(-)/KDR(+) cells), the presence of VDR and the determinants of VDR expression on EPCs, in particular in calcitriol therapy. Methods: EPC counts, percentages of VDR-positive EPCs and VDR expression were assessed by flow cytometry. Cells isolated from a subgroup of patients were cultured to analyze colony-forming units, specific markers expression and a capillary-like structure formation. Results/Conclusions: Our study demonstrates the presence of VDR on EPCs. In our dialysis patients, the parameters studied on both CD34(+)/CD133(+)/KDR(+) and CD34(+)/CD133(-)/KDR(+) cells, in particular VDR expression, seem to be influenced by uremia-related factors, including anemia, inflammation, diabetes, 25(OH)D serum levels and calcitriol therapy.