The biochemical characterization of aggrecan from normal and tibial-dyschondroplastic chicken growth-plate cartilage.

Tibial dyschondroplasia (TD) is a disorder of endochondral ossification characterized by the presence of an avascular, non-mineralized cartilage lesion extending from the growth plate into the metaphysis. Cells within the TD growth plate fail to differentiate to full hypertrophy, and instead appear to maintain a 'pre-hypertrophic' or 'transitional' status. Studies of the expression and distribution of cartilage matrix macromolecules in the TD growth plate have shown a marked decrease in the levels of aggrecan in the TD matrix. In the present study we compared the biochemical characteristics of the aggrecan molecules extracted from normal epiphyseal and TD cartilage. We have shown three major differences between normal and TD cartilage aggrecan. These are: (1) increase in molecular mass; (2) increase in the number of keratan sulphate chains; and (3) difference in the pattern of sulphation in TD aggrecan. Such changes in biochemical characteristics of the aggrecan monomers in TD cartilage may be associated with the lack of mineralization of the diseased cartilage. The present study provides a basis for further investigations into the importance of proteoglycans in normal and pathological bone development.