Changes in sulfation patterns of chondroitin sulfate in equine articular cartilage and synovial fluid in response to aging and osteoarthritis

Abstract

Objectives To determine effects of aging on sulfation of chondroitin sulfate (CS) in articular cartilage and synovial fluid from normal equine middle carpal joints, and to determine whether CS compositional analysis can be used to assess alterations in proteoglycan turnover in degenerative cartilage obtained from horses with carpal osteochondral fractures. Sample Population Carpal articular cartilage and synovial fluid from 44 cadavers with normal joints and from 16 Thoroughbred racehorses during routine carpal arthroscopic surgery. Procedure After papain/chondroitinase digestion of cartilage, CS disaccharides (unsulfated disaccharide ΔDi0S, and monosulfated disaccharides ΔDi4S and ΔDi6S) were quantified by capillary zone electrophoresis. The CS was purified from synovial fluid chondroitinase digested, and analyzed. The CS nonreducing terminal residues, N-acetylgalactosamine (galNAc) or glucuronic acid adjacent to a 4-sulfated or 6-sulfated galNAc, were quantified. Results In cartilage, the ΔDi6S-to-ΔDi4S ratio increased with age; in degenerative cartilage, this ratio was not significantly different from the normal value. Percentage of ΔDi0S decreased with age and was significantly higher in degenerative than in normal cartilage. The galNAc4S and galNAc4,6S represented > 96% of the terminal residues. There was a significant decrease in 6-sulfation of the terminal residues in degenerative cartilage. Conclusions 6-Sulfation of internal and terminal CS residues increased with age. Cartilage degeneration in racehorses was accompanied by deposition of CS chains with altered sulfation patterns. In normal and diseased joints of horses > 2 years old, synovial fluid CS was not indicative of cartilage CS and may represent turnover products of a subpopulation of proteoglycan within the matrix. (Am J Vet Res 1998;59:786-791)