Biosynthesis and distribution of fibronectin in normal and osteoarthritic human cartilage.

The biosynthesis of fibronectin was determined in explants from normal and osteoarthritic human cartilage after metabolic labeling and immunoprecipitation. Each sample of osteoarthritic cartilage was divided into three regions taken at different distances from the eburnated bone area. Only full depth cartilage samples were taken into consideration. We could detect a low level of fibronectin biosynthesis in normal cartilage. In osteoarthritic cartilage increased synthesis of fibronectin was demonstrated, the most important in the region close to the eburnated area. Increased synthesis, although to a lower extent, was also demonstrated in the two other regions at increasing distances from the eburnated areas. Immuno-histological examinations performed on tissue samples and similar studies on articular chondrocyte cell cultures confirmed the accumulation of newly synthesized fibronectin in pathological conditions.