The synthesis and accumulation of fibronectin by human articular cartilage.

Fibronectin was extracted from cartilage under denaturing conditions at concentrations of 1.5 and 15 micrograms/g wet weight for normal and osteoarthritic cartilage, respectively (i.e., there was a 10-fold increase in osteoarthritic cartilage). Heterogeneity on ion exchange and gelatin affinity chromatography and on agarose electrophoresis was consistent with the suggestion that it interacts strongly with elements of proteoglycans. Aggregation of cartilage proteoglycan by addition of hyaluronic acid also aggregated the endogenous fibronectin. Synthesis of fibronectin was identified in explants of normal cartilage by immunoprecipitation and electrophoresis. We conclude that cartilage fibronectin is a normal component of human cartilage and a normal product of mature chondrocytes.