Human Arthritic Synovial Fluid Influences Proteoglycan Biosynthesis and Degradation in Organ Culture of Bovine Nasal Cartilage

The influence of synovial fluid and serum from patients with inflammatory joint disease on proteoglycan metabolism was studied in organ culture of bovine nasal cartilage. Proteoglycan biosynthesis, i.e. incorporation of [³⁵S] -sulphate, was reduced after addition of synovial fluid from rheumatoid arthritis and reactive arthritis patients. Also some rheumatoid arthritis sera but no reactive arthritis serum reduced the biosynthesis compared to control sera. Proteoglycan degradation, i.e. release of proteoglycans prelabelled with [³⁵S] -sulphate, as well as release of proteoglycans determined by.chemical methods, was highest under the influence of rheumatoid arthritis synovial fluid. This effect appears to represent an activity truly stimulating degradation, since added control serum did not prevent the effect. The lowest proteoglycan degradation was observed in culture medium only. Addition of synovial fluid compared to addition of control serum did not increase proteoglycan degradation in freeze-killed cartilage indicating that the effect requires living cells.

The findings are consistent with the presence in synovial fluid of mediators stimulating the chondrocytes both to activate proteoglycan degradation and to reduce proteoglycan biosynthesis.