Pro-and anti-inflammatory cytokine profiles in osteoarthritis

The presence and production of soluble factors in the osteoarthritic (OA) joint have always been a focus of research, as they are assumed to play a role in initiation and/or progression of disease. Many tissue and cell types in the joint are capable of their production, with the synovial fluid serving as a reservoir into which they can be secreted. Although an increasing interest is directed towards chemokines, growth factors and adipokines, traditionally, a subset of inflammatory, anti-inflammatory and modulatory cytokines has been studied. Differential profiles compared to healthy joints were found in the knee and other OA joints, whereby also joint damage induces a specific change in secretory pattern. However, for the cytokines commonly assumed to play a role in OA, such as IL-1 and TNFa, their consistently low levels, frequent lack of association with disease and the presence of natural inhibitors suggest that other soluble factors may be more promising as possible targets.