TLR2 Promotes Vascular Smooth Muscle Cell Chondrogenic Differentiation and Consequent Calcification via the Concerted Actions of Osteoprotegerin Suppression and IL-6–Mediated RANKL Induction

Objective— Vascular smooth muscle cell (VSMC) transformation to an osteochondrogenic phenotype is an initial step toward arterial calcification, which is highly correlated with cardiovascular disease–related morbidity and mortality. TLR2 (Toll-like receptor 2) plays a pathogenic role in the development of vascular diseases, but its regulation in calcification of arteries and VSMCs remains unclear. We postulate that TLR2-mediated inflammation participates in mediating atherosclerotic arterial calcification and VSMC calcification. Approach and Results— We found that ApoE−/−Tlr2−/− genotype in mice suppressed high-fat diet–induced atherosclerotic plaques formation during initiation but progressively lost its preventative capacity, compared with ApoE−/− mice. However, TLR2 deficiency prohibited high-fat diet–induced advanced atherosclerotic calcification, chondrogenic metaplasia, and OPG (osteoprotegerin) downregulation in the calcified lesions. Incubation of VSMCs in a calcifying medium revealed that TLR2 ag...