Comparison of keratan sulphate concentrations and the size distribution of proteoglycans in the synovial fluid of patients with osteoarthritis and pyrophosphate arthropathy.

In order to evaluate the effect of calcium pyrophosphate dihydrate (CPPD) deposition on articular cartilage catabolism, the proteoglycans released into normal synovial fluid were compared with those in synovial fluid obtained from patients with osteoarthritis (OA), chronic pyrophosphate arthropathy (CPA) and acute pyrophosphate arthropathy (APA). Keratan sulphate (KS) was measured by the modified 1,9-dimethylmethylene blue (DMB) assay in synovial fluids treated with chondroitin ABC lyase. This enzyme was found to eliminate all of the sulphated glycosaminoglycans in synovial fluid except KS. In OA, CPA and APA the concentrations of KS were found to be significantly higher than in normal synovial fluid (NSF) (P less than 0.01). Similar KS concentrations were observed in CPA and APA. In CPA they were significantly higher than in OA (P less than 0.02). The size distribution of proteoglycan fragments varied between different patients with the same disease, but only minor differences were observed in patients with OA and CPA who were matched for age, sex and disease severity. Furthermore, the size distribution of proteoglycan fragments in the acute and chronic phases of pyrophosphate arthritis was similar. Thus although in pyrophosphate arthritis the rate at which proteoglycans are released from the cartilage may be greater than in OA or normal joints, the fundamental processes governing the release of these macromolecules may be the same.