Review Question - QID 5800

TGF-beta 1 stimulates the synthesis of extracellular matrix (ECM) and causes synovial proliferation and fibrosis.

TGF-beta is the most thoroughly investigated member of the TGF-beta superfamily. This group includes TGF-beta1, BMP-2, and BMP-7. Besides the above activities, TGF-beta1 also stimulates chondrocyte synthetic activity and decreases the catabolic activity of IL-1.

Fortier et al. reviewed the role of growth factors in cartilage repair and modification of osteoarthritis. They found that members of the TGF-beta superfamily, FGF family, IGF1, and PDGF have all been investigated as possible treatment augments in the management of chondral injuries and early arthritis. They concluded that more research was necessary before routine application.

Illustration A shows a summary of the different growth factors and their effects on cartilage.

Incorrect Answers:
Answer 1: IL-1 is catabolic and leads to cartilage breakdown rather than synthesis.
Answer 2: TNF-alpha is a proinflammatory cytokine. It does not lead to cartilage synthesis.
Answer 3: Although FGF-2 increases proteoglycan synthesis and cell proliferation, it also increases inflammation and osteophyte formation and does not aid in healing of cartilage defects. FGF-18 is less well studied.
Answer 5: PDGF has no adverse or positive effects on cartilage when used in vivo. Much evidence on its role is extrapolated from the effects of PRP.