Role of osteogenic circulating endothelial progenitor cells in dissemination of large arterial calcification in rheumatoid arthritis

Abstract

Background: Rheumatoid arthritis is associated with both abnormal bone metabolism and atherogenesis but mechanistic links were missing. Aim: This study aimed to investigate the role of osteocalcin (OCN)-expressing circulating endothelial progenitor cells (EPC)s in the severity and dissemination of systemic arterial calcifications in rheumatoid arthritis. Methods: We performed flow cytometry studies in 145 consecutive patients with rheumatoid arthritis to determine osteogenic circulating levels of OCN-positive (OCN+) CD34+KDR+ and OCN+CD34+, versus conventional early EPC CD34+CD133+KDR+. Total calcium load of the thoracic aorta (ascending plus descending) and the carotid arteries were assessed by non-contrast computed tomography (CT) and contrast CT angiography. Results: Osteogenic EPCs OCN+CD34+KDR+ (P=0.002) and OCN+CD34+ were strikingly associated with the clustered presence of aortic and carotid calcification (P=0.002 and 0.001 respectively, Figure). Multivariable analyses revealed that circulating OCN+CD34+KDR+ (B=14.4 [95% CI 4.0 to 24.8], P=0.007) and OCN+CD34+ (B=9.6 [95% CI 4.9 to 14.3], P<0.001) remained independently associated with increased aortic calcium load. OCN+CD34+ EPC (B=0.8 [95% CI 0.1 to 1.5], P=0.023), but not OCN+CD34+KDR+ EPC (B=1.2 [95% CI −0.2 to 2.6], P=0.09) was further independently associated with carotid calcium load. In comparison, conventional early EPC CD34+CD133+KDR+ had no significant association with aortic or carotid calcium load (P=0.46 and 0.88, respectively). Conclusions: Circulating level of osteogenic EPC is associated with promulgated aortic and carotid calcification in patients with rheumatoid arthritis, suggesting a potential mechanistic role of the bone-vascular axis in pro-atherogenicity of rheumatic diseases.