LOSS OF DECORIN FROM THE SURFACE ZONE OF ARTICULAR-CARTILAGE IN A CHICK MODEL OF OSTEOARTHRITIS

The objective of this study was to immunolocalize decorin and to asses s changes as a result of pyridoxine (PN) deficiency in chick articular cartilage from femoral condyles. After maintenance on a normal diet f or the first two weeks after hatching, 15 broiler chickens were depriv ed of this vitamin for 6 weeks. It was previously shown that the ankle joints of PN-deficient animals are swollen with effusions. They also present an abnormal gait, enlarged bony margins, and fissuring of the articular cartilages. Milder changes (no fissures) were also shown in the knee joints. Data from a previous study were suggestive that sulfa ted glycosaminoglycans are lost from the knee cartilage surface into s ynovial fluid. The current study was focused on the small proteoglycan , decorin, which coats the surface of collagen fibrils and may regulat e their morphology. To examine decorin in normal and PN-deficient arti cular cartilage, a monoclonal antibody to an epitope on the protein co re of decorin was used for immunohistochemical staining of tissue sect ions and for Western Blot analysis of cartilage extracts. Reduction of staining with the antibody was demonstrated in the tangential surface zone of PN-deficient cartilage, and Western Blot analysis showed redu ced intensity of decorin bands compared to normal controls. These data suggest that a lack of decorin may play a role in the enlargement of collagen bundles in the tangential zone of PN-deficient articular cart ilage as observed in a previous electron microscopic study.