Fibronectin as a marker for osteoarthritis.

Abnormal cartilage from osteoarthritic canine joints contained up to 20 times more fibronectin than did disease-free cartilage. Fibronectin synthesis in osteoarthritic cartilage was increased and more of the newly made protein accumulated in this cartilage. Data suggested that fibronectin content was increased in cartilage with early osteoarthritic changes whereas glycosaminoglycan content remained unchanged. Immunoperoxidase studies revealed that fibronectin was distributed throughout the matrix of both normal and osteoarthritic cartilage. Fibronectin concentration was increased twofold in synovial fluid from osteoarthritic joints.