Osteogenic circulating endothelial progenitor cells are linked to electrocardiographic conduction abnormalities in rheumatic patients.

Abstract

Osteogenic circulating endothelial progenitor cells (EPC) play a pathogenic role in cardiovascular system degeneration through promulgating vasculature calcification, but its role in conduction disorders as part of the cardiovascular degenerative continuum remained unknown. To investigate the role of osteocalcin (OCN)-expressing circulating EPCs in cardiac conduction disorders in the unique clinical sample of rheumatoid arthritis (RA) susceptible to both abnormal bone metabolism and cardiac conduction disorders. We performed flow cytometry studies in 134 consecutive asymptomatic patients with rheumatoid arthritis to derive osteogenic circulating OCN-positive (OCN+) CD34+KDR+ vs. CD34+CD133+KDR+ conventional EPC. Study endpoint was the prespecified combined endpoint of electrocardiographic conduction abnormalities. Total prevalence of cardiac conduction abnormality was 9% (n=12). All patients except one had normal sinus rhythm. One patient had atrial fibrillation. No patient had advanced atrioventricular (AV) block. Prevalence of first-degree heart block (>200ms), widened QRS duration (>120ms) and right bundle branch block were 6.7%, 2.1%, and 2.2% respectively. Circulating osteogenic OCN+ CD34+ KDR+ EPCs were significantly higher among patients with cardiac conduction abnormalities (p=0.039). Elevated OCN+ CD34+ KDR+ EPCs> 75th percentile was associated with higher prevalence of cardiac conduction abnormalities (58.3% vs. 20.02%, p=0.003). Adjusted for potential confounders, elevated OCN+ CD34+ KDR+ EPCs> 75th percentile remained independently associated with increased risk of cardiac conduction abnormalities (OR=4.4 [95%CI 1.2-16.4], p=0.028). No significant relation was found between conventional EPCs CD34+CD133+KDR+ and conduction abnormalities (p=0.36). Elevated osteogenic OCN+ CD34+ KDR+ EPCs are independently associated with the presence of electrocardiographic conduction abnormalities in patients with rheumatoid arthritis, unveiling a potential novel pathophysiological mechanism.