Therapeutic effects on cartilage metabolism in arthritis as measured by release of proteoglycan structures into the synovial fluid.

Proteoglycans are molecules that are degraded and released from the articular cartilage into the synovial fluid early in an arthritic process. Such released proteoglycans were quantified by an enzyme linked immunosorbent assay (ELISA). The proteoglycan content in synovial fluid from patients with various knee joint arthritides was constant in two samples withdrawn five days apart. To determine if therapeutic measures were paralleled by effects directly on the articular cartilage the patients were treated with local injections of glucocorticoids. In all patients the glucocorticoids induced a reduction of the proteoglycan content in the synovial fluid, reflecting their effects on the cartilage. In two patients with spontaneous remission of their arthritis a reduction in the proteoglycan content in the synovial fluid was also noted. The quantification of proteoglycans in synovial fluid appears to have potential as a useful tool for monitoring the effects of therapy on cartilage metabolism.