Comparative study on circulating endothelial progenitor cells in systemic lupus erythematosus patients at active stage.

Circulating endothelial progenitor cells (CEPCs) play an important role in the process of atherosclerosis. Most previous studies on CEPC in systemic lupus erythematosus (SLE) patients were on their number and some functions and the results were not consistent. No studies on their anti-inflammatory function and integrated status were reported. The purpose of this study was to determine the number, function (including anti-inflammatory function), and the integrated status of CEPCs in active SLE patients. The study was performed in 35 active SLE patients (28 females, 7 males) and 35 age-and gender-matched healthy controls. CEPC number was determined by Fluorescence-Activated Cell Sorting. Proliferation capacity of CEPC was assessed by PCNA staining. Adhesion capacity of CEPC to fibronectin and adhesion capacity of THP1 cell to CEPC were determined by cell adhesion assay. Migratory capacity of CEPC was measured by transwell chamber assay and the potential to form tubes on Matrigel of CEPC was determined by in vivo tube formation on Matrigel test. The expression of inducible nitric oxide synthase (iNOS) and interleukin-6 (IL-6) assessed by quantitative PCR as well as the expression of intercellular adhesion molecule-1 (ICAM-1) and phosphorylated-Akt (p-Akt) assessed by western-blotting were used to evaluate the anti-inflammatory function and cell status of CEPCs. The number of CEPC in SLE patients was not different from that in control (p > 0.05). Proliferation capacity of CEPC was decreased in active SLE patients (p = 0.027). Adhesion capacity of CEPC to fibronectin was decreased (p = 0.04) in SLE patients and adhesion capacity of THP1 cell to CEPC was increased in SLE patients (p < 0.001). Migratory activity was reduced in patient CEPCs (p < 0.001). Capacity of CEPCs to form tube on Matrigel was decreased in SLE patients (p < 0.001). Expression of iNOS and IL-6 (p < 0.001, p = 0.006, respectively) and ICAM-1 were increased in CEPC of SLE patients and expression of p-Akt was decreased in CEPC of SLE patients. Our data show that CEPC number in active SLE patients was not significantly different from healthy controls, but their functions were partly impaired, including proliferation, adhesion, migration, and tube formation. Bad cell status and increased susceptibility to inflammatory process of CEPCs in active SLE were also observed in our study.