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

Tibial dyschondroplasia (TD) is a disorder of endochondral ossification cha racterized by the presence of an avascular, nonmineralized cartilage lesion extending from the growth plate into the metaphysis. Cells within the TD g rowth plate fail to differentiate to full hypertrophy, and instead appear t o maintain a 'prehypertrophic' or 'transitional' status. Studies of the exp ression and distribution of cartilage matrix macromolecules in the TD growt h plate have shown a marked decrease in the levels of aggrecan in the TD ma trix. In the present study we compared the biochemical characteristics of t he aggrecan molecules extracted from normal epiphyseal and TD cartilage. We have shown three major differences between normal and TD cartilage aggreca n. These are: (1) increase in molecular mass; (2) increase in the number of keratan sulphate chains; and (3) difference in the pattern of sulphation i n 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 i nvestigations into the importance of proteoglycans in normal and pathologic al bone development.