Roles of TGF-beta 1 signaling in the development of osteoarthritis.

Osteoarthritis (OA) is a degenerative joint disorder characterized by the destruction of articular cartilage, subchondral bone and other joint tissues. Although multiple growth factors and cytokines have been shown to be involved in articular cartilage degeneration and subchondral bone destruction, which eventually leads to OA, the molecular mechanisms underlying the pathogenesis of OA are largely unknown. The canonical transforming growth factor beta 1 (TGF-β1) signaling functions as one of the key factors in cartilage and bone formation, remodeling, and maintenance. However, the effects of TGF-β1 signaling on the development of OA are unclear. Numerous studies provide evidence that TGF-β1 is required for the formation of articular cartilage at early stages of joint development. In contrast, other investigations indicate that TGF-β1 may, in fact, be a factor in joint destruction. Therefore, we, in this review article, discuss the "conflicting" roles of TGF-β1 signaling in the development of OA.