Presence of small proteoglycan fragments in normal and arthritic human cartilage

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Abstract
Objective. To characterize the small proteoglycans decorin and biglycan in normal human patellar cartilage and in cartilage from individuals with chronic polyarthritis. Methods. Cartilage extracts were chromatographed on DEAE-Trisacryl and further separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis before and after enzymatic degradation of the glycosaminoglycan chains. Decorin and biglycan were visualized after Western blotting, using core protein-specific polyclonal and monoclonal antibodies. Results. Core protein fragments of both proteoglycans were observed even in normal cartilage. In the case of decorin they amounted to up to 15% of the immunoreactive material, and up to 5% of the core protein was glycosaminoglycan free. The quantity of decorin core protein was reduced in arthritic cartilage, but the core protein fragments represented up to 45% of the immunoreactive material. Different zones of cartilage differed in their content of the fragments. Evidence for an increased proportion of biglycan fragments was not obtained. Conclusion. Chronic polyarthritis leads to increased degradation of small proteoglycans. A considerable proportion of decorin fragments is retained in the tissue. These alterations may have a negative influence on the mechanical stability of tissue.

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