Catabolism of aggrecan, decorin and biglycan in tendon

We have examined the catabolism of the proteoglycans aggrecan, decorin and biglycan in fresh tendon samples and in explant cultures of tissue from the tensional and compressed regions of young and mature bovine tendons. A pan el of well-characterized antibodies that recognize glycosaminoglycan or pro tein (linear or neoepitope) sequences was used to detect proteoglycans and proteoglycan degradation products that were both retained within the tissue and released into the culture medium. In addition, a reverse-transcriptase -mediated PCR analysis was used to examine the mRNA expression patterns of tendon proteoglycans and aggrecanases. The results of this study indicate a major role for aggrecanase(s) in the catabolism of aggrecan in bovine tend on. The study also provides a characterization of glycosaminoglycan epitope s associated with the proteoglycans of tendon, illustrating age-related cha nges in the isomers of chondroitin sulphate disaccharides that remain attac hed to the core protein glycosaminoglycan linkage region after digestion wi th chondroitinase APC. Evidence for a rapid turnover of the small proteogly cans decorin and biglycan was also observed, indicating additional molecula r pathways that might compromise the integrity of the collagen matrix and p otentially contribute to tendon dysfunction after injury and during disease .