Evaluation of the role of keratan sulphate as a molecular marker to monitor cartilage metabolism in horses

The role of keratan sulphate (ICS) as a metabolic marker of cartilage was e valuated using an in vitro model of equine articular cartilage. Articular c artilage was harvested from clinically healthy 6-month-old foals (n = 3). C hondrocytes were centrifuged and cultured as pellets. Chondrocyte pellets w ere stimulated by insulin-like growth factor-I alpha (IGF-I alpha) or inter eukin-1 alpha (IL-1 alpha) for 2 weeks. The concentrations of sulphated gly cosaminoglycans (GAG) and KS in the culture media were measured by a 1,9-di methylmethylene blue (DMMB) colorimetric assay and an inhibition enzyme-lin ked immunosorbent assay using a 1/20/5D4 antibody, respectively. The concen tration of GAG was significantly increased both in the media of pellets sti mulated by IGF-1 alpha and in those stimulated by IL-1 alpha. KS concentrat ion was significantly increased in those stimulated by IL-1 alpha, while no significant change was found in those stimulated by IGF-I alpha. A high co rrelation between GAG and KS concentrations was found in the media of pelle ts stimulated by IL-1 alpha (r = 0.84), but not in those stimulated by IGF- I alpha (r = 0.59). The results suggest that the concentration of KS reacti ng to 1/20/5D4 mirrors the GAG concentration during the stage of cartilage catabolism, but not during the cartilage anabolic stage. The KS concentrati on in biological fluids could therefore be a useful marker to understand fu rther the cartilage catabolic process. It may also represent some aspects o f the cartilage anabolic process.