Immunohistochemical study of a chondroitin-6-sulfate in growth plates of broiler chickens with high and low genetic predispositions to tibial dyschondroplasia

The distribution of a chondroitin-6-sulfate (C6S) epitope, which is a biochemical marker of chondrocyte hypertrophy, was studied in the growth plates of two lines of 3-week-old broiler chickens with low and high genetic predispositions to tibial dyschondroplasia (TD). Ultrathin sections of growth plates from both groups were subjected to immunolocalization with monoclonal antibody 3-B-3(-), the epitope of which is increased on proteoglycans made by hypertrophic chondrocytes. Bound antibody was localized with colloidal gold-labeled protein A for observation with an electron microscope. The 3-B-3(-) epitope was localized in pericellular and interterritorial matrix of growth plates of both lines. In the low-TD-incidence birds, the concentration of 3-B-3(-) bound to C6S progressively increased from the proliferative zone to the hypertrophic zone. However, in the high-TD-incidence line, the epitope expression remained at a low level in all zones. The increase of the 3-B-3(-) epitope produced by maturing growth-plate chondrocytes is indicative of changes in the glycosaminoglycan chains of proteoglycans that may be important in the process of matrical calcification. Thus, failure of chondrocytes of the high-TD-incidence line to produce this change in post-translational modification of their proteoglycans could be important in the pathological process.