High Adiponectin and Adiponectin Receptor 1 Expression in Synovial Fluids and Synovial Tissues of Patients with Rheumatoid Arthritis

ObjectivesThe major objectives of this article are first to measure the levels of expression of adiponectin and its 2 receptors (adipoR1 and adipoR2) in the peripheral blood mononuclear cells and in the synovial compartment of rheumatoid arthritis (RA) patients, and second, to assess their pro-inflammatory potential. Osteoarthritis patients and healthy subjects served as controls.MethodsExpression of adiponectin, adipoR1, and adipoR2 were assayed by real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and immunohistology. The potential pro-inflammatory activity of adiponectin was studied by adding recombinant adiponectin to cultures of synovial fibroblasts.ResultsImmunohistology showed that numerous cells in the synovial biopsies of RA expressed adiponectin, adipoR1, and adipoR2. The synovial fibroblasts were distinctly rich in adiponectin. As expected, high adiponectin levels were present in the synovial fluids. In contrast to the synovial compartment, in peripheral blood mononuclear cells, only adipoR1 exceeded those of osteoarthritis and healthy subjects. When recombinant adiponectin was added to cultures of synovial fibroblasts, it induced up to 8.1- and 11.4-fold increase in the release of monocyte chemoattractant protein-1 and interleukin-6.ConclusionsThe adiponectin adipokine axis might play a role in RA.