Soluble osteopontin and vascular calcification in hemodialysis patients

Background: Vascular calcification often occurs in patients with uremia. As osteopontin (OPN) is not only involved in the physiological but also the p athological calcification of tissues, OPN may be associated with the pathog enesis of aortic calcification in hemodialysis (HD) patients. Methods: We e xamined the expression of OPN in atherosclerotic aortas of HD patients. In addition, we performed a prospective longitudinal study by using CT scans t o detect aortic calcifications and by measuring the plasma OPN concentratio n by ELISA in HD patients (20 men, 16 women; mean age 55.2 +/- 21.3 years) and in healthy volunteers (18 men, 17 women; mean age 54.0 +/- 13.2 years). Results: By immunohistochemical staining, OPN was abundantly localized in atherosclerotic plaques of HD patients. The macrophages surrounding the ath eromatous plaques were identified as the OPN-expressing cells. We furthermo re found that the concentration of soluble plasma OPN was significantly hig her in HD patients as compared with the concentrations in age-matched healt hy volunteers (837.3 +/- 443.2 vs. 315.1 +/- 117.4 ng/ml, p < 0.01). The OP N concentration was positively correlated with the aortic calcification ind ex in HD patients (r = 0.749, p < 0.01). Conclusion: These data suggest tha t OPN, secreted by macrophages, plays a role in the calcification of athero matous plaques in HD patients. Copyright (C) 2001 S. Karger AG, Basel.