ABSTRACT
This chapter reviews recent studies on roles of fibroblast growth factor (FGF) and transforming growth factor-ß (TGF--ß) families in development, growth, and remodeling of cartilage. FGF and TGF-ß are mitogenic for chondrocytes and have a profound effect on their cytodifferentiation. FGF and TGF-ß synthesized by chondrocytes may serve as autocrine regulators. Chondrocytes grown on plastic or glass dishes progressively transform into motile cells that are morphologically indistinguishable from fibroblasts. More than 50% of rabbit chondrocytes became fibroblastic after proliferation for four generations on plastic culture dishes. TGF-ß inhibits production of plasminogen activator, collagenase, and stromelysin, while stimulating production of plasminogen activator inhibitor and TIMP in several cell types. TGF-ß is present in the hematoma at a site of bone fracture. TGF-ß implanted at subcutaneous or intramuscular sites of the rat did not induce cartilage or bone, but TGF-ß plus a bone-derived osteoinductive factor induced ectopic bone formation at intramuscular sites.
