Objective Patients with cardiorenal syndrome (CRS) have high cardiovascular morbidity. Endothelial progenitor cells (EPC) constitute an endogenous vascular repairsystem, protecting against atherosclerosis development. Erythropoietin (EPO) treatment may have beneficial effects by mobilizing EPC from the bonemarrow. Our objective is to determine EPC levels and effects of EPO therapy on EPC levels in CRS patients.

Design Open-label randomized trial.

Setting Part of the EPOCARES-trial, conducted in Utrecht (Netherlands).

Patients Patients with CRS and anaemia and healthy controls were included.

Interventions Patients were randomized to receive EPO therapy (50 IU/kg/wk) for 52 weeks or no EPO therapy.

Main outcome measures CD34⁺KDR⁺-EPC, cultured EPC outgrowth and function at baseline, after 18 days and after 52 weeks.

Results Patients showed lower CD34⁺KDR⁺-cell numbers compared to controls (6(12) vs. 19(19) cells/10⁵ granulocytes; p=0.010), despite increased levels of stromal cell-derived factor-1α; (3.1(0.8) vs 2.6(0.3) ng/ml; p=0.001). EPC outgrowth and function were not different between patients and controls. EPC levels did not change after 18 days with or without EPO treatment. CD34⁺KDR⁺-cells significantly declined after 52 weeks in the non-treated group (p=0.028). Long-term EPO therapy did not significantly affect this reduction in CD34⁺KDR⁺-EPC levels.

Conclusions CRS patients showed reduced CD34⁺KDR⁺-EPC levels compared to controls, consistent with a reduced vascular regenerative potential and despite upregulated SDF-1α levels. Over a one-year follow-up period a marked 68% further reduction in EPC levels was observed in the patient group without EPO treatment. In spite of promising experimental studies, our longitudinal, randomized study did not show significant influence of either short- or long-term EPO therapy on reduced EPC levels in CRS patients.