Changes in glycosaminoglycan epitope levels in knee joint fluid following injury.

OBJECTIVE: To measure the levels of epitope on the chondroitin sulfate (CS) and keratan sulfate (KS) chains of proteoglycan fragments in synovial fluids from injured and contralateral uninjured knees of patients with traumatic cruciate ligament and/or meniscus damage. METHODS: Enzyme-linked immunosorbent assays were used to determine the levels of monoclonal antibody epitopes 3-B-3 and 7-D-4 (CS), and 5-D-4 (KS), in paired joint fluids from the injured and uninjured knees of trauma patients. RESULTS: Levels of the CS epitopes were increased in the trauma joint fluids from most patients, with higher levels of 3-B-3 epitope in 12 of the 16 patients, but the difference did not achieve significance; however, 7-D-4 levels were higher in 15 patients, and the difference was highly significant (P = 0.0005). In contrast, the KS epitope detected by 5-D-4 was decreased in 13 of 15 patients, and the difference was significant (P = 0.0074). CONCLUSION: The increased level of 7-D-4 epitope on proteoglycans in joint fluid from injured knees may reflect the response of the articular cartilage to acute trauma resulting in altered expression of specific CS epitopes on cartilage proteoglycans. The fall in KS epitope levels may reflect the synthesis of proteoglycans that have lower KS content.

The sulphation pattern in chondroitin sulphate chains investigated by chondroitinase ABC and ACII digestion and reactivity with monoclonal antibodies.

We have used progressive chondroitinase digestion of pig aggrecan in conjunction with ELISA assays and disaccharide analysis to derive information about the pattern of 4- and 6-sulphation in chondroitin sulphate chains. Digestion with chondroitinase ABC resulted in the release of mainly disaccharides from the nonreducing terminal of chondroitin sulphate chains but there was also the release of some tetra- and hexa-saccharides which were degraded to disaccharides with more extensive digestion. Chondroitinase ACII, in contrast, released only disaccharides. Analysis of the disaccharide composition of the intact and digested products at different stages of digestion showed that there was a slight increase in 6-sulphate content of the chains as they were shortened. Reaction of the partially digested proteoglycans with monoclonal antibodies 3-B-3 and 3-D-5 which recognise chains terminating in 6- or 4-sulphated disaccharides, respectively, showed major differences between chondroitinase ABC and ACII products. The results suggested that chondroitinase ABC preferentially cleaved next to 4-sulphated, rather than 6-sulphated disaccharides and this resulted in some oligosaccharides as well as disaccharide being released. Chondroitinase ACII also cleaved an additional disaccharide next to the linkage to protein of chondroitin sulphate, which was not removed by chondroitinase ABC and this disaccharide was mainly nonsulphated.