Osteoprotegerin/RANK/RANKL axis and atrial remodeling in mitral valvular patients with atrial fibrillation

BackgroundAtrial remodeling is considered as the structural basis for the development and sustaining of atrial fibrillation (AF). Osteoprotegerin (OPG)/receptor activator of nuclear factor-κB (RANK)/RANK ligand (RANKL) axis, a key regulatory system in bone metabolism, was recently identified in some cardiovascular disorders for its regulation to myocardial remodeling. We hypothesized that the OPG/RANK/RANKL axis is involved in development and perpetuation of AF by regulating atrial remodeling.MethodsBiopsies of right atrial appendage and clinical data were collected from sex- and age-matched 24 persistent AF, 24 paroxysmal AF, 24 sinus rhythm (SR) patients undergoing isolated mitral valve surgery and 24 healthy heart donors (normal controls).ResultsA significantly increasing gradient of atrial expression of OPG, RANKL, RANK and RANKL/OPG ratio was identified in normal controls, SR and AF groups. RANKL/OPG ratio was also found significantly higher in paroxysmal AF than persistent AF. Furthermore, atrial expression and activity of the axis was statistically correlated with collagen III/I levels and ratio and the degree of interstitial fibrosis reflected by collagen volume fraction in right atrial appendages.ConclusionsThe present findings suggest a potential role for known mediators of bone homeostasis in the pathogenesis of AF and possibly represent new targets for therapeutic intervention in AF.