Abstract: CHEN Hong*, ZHAO Hui-juan, MEN Jian-long. *Department of Biomedical Engineering, College of Precision Instrument and Opto-electronics Engineering, Tianjin University, Tianjin 300120, China 【Abstract】 Objective To characterize the alteration in peripheral blood endothelial progenitor cells （EPCs） of patients with systemic lupus erythematosus （SLE）. Methods Venous blood samples were obtained from 82 female patients with SLE aged （35 ± 10） years and 50 healthy female controls aged （35 ± 13） years. ACL 9000 automated coagulation analyzer was used to determine the level of Von Willebrand factor antigen （vWF Ag）. Flow cytometry was performed to detect peripheral blood EPCs and circulating endothelial cells （CECs）. Analysis of variance was performed to assess the differences in these parameters between patients with active and stable SLE and the controls, and Pearson correlation analysis was conducted to evaluate the relationship between these parameters. Results The number of CD34+ cells, CD133+ cells and CD34+CD133+ cells per 200 000 peripheral blood mononuclear cells was 35.4 ± 16.7, 86.5 ± 32.1 and 361.3 ± 176.4 in patients with active SLE, significantly higher than that in the patients with stable SLE （17.1 ± 10.9, 28.7 ± 21.5, 107.2 ± 44.3, respectively, all P < 0.01）） and the controls （13.8 ± 9.6, 11.2 ± 5.5, 92.3 ± 50.5, respectively, all P < 0.01）. The patients with active SLE exhibited an elevated level of vWF Ag （438.9% ± 205.3% vs. 130.2% ± 51.5%, P < 0.01）, an increased number of EPCs （361.3 ± 176.4 vs. 107.2 ± 44.3, P < 0.01） but a similar number of CECs （127±51 vs. 118 ± 39, P > 0.05） per 200 000 peripheral blood mononuclear cells compared with the healthy controls. No significant differences were observed in these parameters between the patients with stable SLE and the controls （all P > 0.05）. The number of EPCs was positively correlated with the level of vWF Ag （r = 0.67, P < 0.01）, but uncorrelated with the number of CECs （P > 0.05） in patients with active SLE. Conclusions The quantity of EPCs in peripheral blood is closely correlated with the level of the vascular injury marker vWF Ag, hinting that the number of EPCs can serve as a useful marker of disease severity.

Key words: endothelial cell