Endothelial progenitor cell dysfunction in patients with progressive chronic kidney disease

Abstract

Endothelial progenitor cells (EPC) contribute to repair and maintenance of the vascular system, but in patients with chronic kidney disease (CKD), the number and function of EPC may be affected by kidney dysfunction. We assessed numbers and the angiogenic function of EPC from patients with CKD in relation to disease progression. In a cross-sectional, prospective study, 50 patients with varying degrees of CKD, including 20 patients undergoing dialysis and 10 healthy controls, were included. Mononuclear cells were isolated, and circulating EPC were quantified by flow cytometry based on expression of CD14 and CD34. EPC were cultured on fibronectin-coated supramolecular films of oligocaprolactone under angiogenic conditions to determine their angiogenic capacity and future use in regenerative medicine. CKD patients had normal numbers of circulating CD14+ EPC but reduced numbers of circulating CD34+ EPC. Furthermore, EPC from patients with CKD displayed functional impairments, i.e., hampered adherence, reduced endothelial outgrowth potential, and reduced antithrombogenic function. These impairments were already observed at stage 1 CKD and became more apparent when CKD progressed. Dialysis treatment only partially ameliorated EPC impairments in patients with CKD. In conclusion, EPC number and function decrease with advancing CKD, which may hamper physiological vascular repair and can add to the increased risk for cardiovascular diseases observed in CKD patients.

Figures

Fig. 1.

Determinants of circulating CD34+ endothelial progenitor cell (EPC) numbers. CD34+ EPC decreased in early stages of chronic kidney disease (CKD) and decreased further during disease progression (A and B). Statin use increased the number of circulating CD34+ EPC (C). Also, hemodialysis treatment resulted in mobilization of CD34+ EPC (D). □, Healthy controls; •, CKD patients; ○, hemodialysis (HD) and peritoneal dialysis (PD) patients. ***P < 0.001 vs. healthy controls.

Fig. 2.

Determinants of circulating CD14+ EPC numbers. CD14+ EPC numbers were similar in CKD patients and healthy controls (A), but the number of CD14+ EPC increased slightly during CKD progression (B). There was no mobilization effect caused by hemodialysis treatment (C). Symbols are as defined for Fig. 1.

Fig. 3.

Adherence and apoptosis of endothelial outgrowth cells. The adherence of endothelial outgrowth cells from patients with CKD was hampered as early as stage 1 (eGFR > 60; A). Dysfunctional adhesion was associated with CKD disease progression (B). Apoptosis of endothelial outgrowth cells did not contribute to reduced adhesion, for apoptosis was similar in all patient groups and healthy controls (C). Increased numbers of CD34+ EPC were associated with increased cell adherence (D) and reduced apoptosis (E). Activation of cells through hemodialysis also increased cell adherence (F). Symbols are as defined for Fig. 1. *P < 0.05 vs. health controls. ***P < 0.001 vs. healthy controls.

Fig. 4.

Endothelial cell differentiation by cultured endothelial outgrowth cells. Endothelial outgrowth cells from patients with CKD lost the ability to differentiate into mature endothelial cells, as indicated by reduced coexpression of CD31 and von Willebrand factor (vWF; A) and CD144 and endothelial nitric oxide synthase (eNOS; B). Although differentiation was affected at the early stages of disease, differentiation capacity decreased progressively during disease progression (C and D). The level of endothelial cell differentiation was associated with the number of CD34+ EPC (E and F) and increased after hemodialysis treatment (G and H). Furthermore, the use of prescribed statins increased endothelial cell differentiation (I and J). Symbols are as defined for Fig. 1. ***P < 0.001 vs. healthy controls.

Fig. 5.

Endothelial cell proliferation and function of cultured endothelial outgrowth cells. Endothelial outgrowth cells from CKD patients showed drastic decreases in cell proliferation (A). Proliferation of endothelial outgrowth cells was associated with the presence of CD34+ EPC (B). Furthermore, endothelial outgrowth cells from end-stage renal failure patients showed reduced antithrombogenic behavior (C), indicating improper maturation. In CKD patients, functional maturation depended partly on the number of circulating CD34+ EPC numbers (D). Symbols are as defined for Fig. 1.