Consideration of the Role of Antigenic Keratan Sulphate Reacting to a 1/14/16H9 Antibody as a Molecular Marker to Monitor Cartilage Metabolism in Horses

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The role of keratan sulphate (KS) as a marker of cartilage metabolism was evaluated by using an in vitro model of equine articular cartilage. Articular cartilage was harvested from clinically healthy 6-month-old foals (n=3). Chondrocytes were centrifuged and cultured as pellets. Chondrocyte pellets were stimulated by insulin-like growth factor (IGF)-Iα or interleukin (IL)-1α for 2 weeks. The sulfated glycosaminoglycans (GAG) and antigenic KS concentrations in the culture media were measured by a 1, 9-dimethyl-methylene blue (DMMB) colorimetric assay and an inhibition ELISA using a 1/14/16H9 antibody, respectively. Concentration of GAG was significantly increased in the media of pellets stimulated by both IGF-Iα and IL-1α. Antigenic KS concentration was significantly increased in those stimulated by IL-1α, while no significant change was found in those stimulated by IGF-Iα. A high correlation between GAG and antigenic KS concentrations was found in the media of pellets stimulated by IL-1α (r=0.87), but not in those stimulated by IGF-Iα (r=0.43). The results suggest that the concentration of antigenic KS reacting to 1/14/16H9 mirrors the GAG concentration during the stage of cartilage catabolism, but not during the cartilage anabolic stage. The concentration of antigenic KS reacting to 1/14/16H9 antibody in biological fluids could therefore be a useful marker to further understand principally the catabolic and slightly the anabolic process of articular cartilage metabolism.