Abstract
Transforming growth factor-beta (TGF-beta) is a cytokine that plays an important role in both normal joints and joints affected by osteoarthritis (OA), the most common joint disease. However, the role of this pleiotropic cytokine in a normal healthy joint is very different from its role in an OA joint. In a normal synovial joint, active TGF-beta is only present after joint loading and only for a short period. In contrast, permanent and high levels of active TGF-beta are detected in OA joints. Due to this difference in levels and exposure period of joint cells to active TGF-beta, the function of TGF-beta is strikingly different in normal and OA joints. The consequences of this difference in TGF-beta levels on joint homeostasis and pathological changes in OA joints are discussed in this review.
