Ultrastructural localisation of fibronectin in human osteoarthritic articular cartilage

A protein A-gold immunolocalisation technique has been used on sections of femoral head articular cartilage to localise fibronectin. Chondroitinase treatment enhanced gold staining, particularly when tissue samples were digested before fixation. The greatest accumulations of fibronectin were seen in the surface zone of osteoarthritic cartilage. Disease free cartilage contained very little fibronectin in this region. Cells which appeared to produce fibronectin were rare in normal specimens but common in the superficial region of osteoarthritic cartilage. These chrondrocytes appeared to release fibronectin as part of an amorphous material which accumulated in the pericellular region. This is the first ultrastructural demonstration of fibronectin synthesis by articular cartilage chondrocytes.