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Wheeless' Textbook of Orthopaedics
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Proteoglycans in Cartilage



- See: cartilage topics

- Discussion:
    - proteoglycan is a macromolecule constructed of a protein core to which many glycosaminoglycan chains are attached;
            - to this proteoglycan aggregate, hyaluronic acid is non covalently bound;
            - in osteoarthritis, there is a characteristic reduction in a aggregrating proteoglycans;
    - about 10% of wt of proteoglycan molecule is protein, and 90% is glycosaminoglycans;
    - negatively chondroitin & keratan sulfate repel each other, so that glycosaminoglycan electrostatic
            repulsion along chain and between chains and therefore chains assume a fully extended conformation;
    - sub-types:
            - aggrecans (large agregating proteoglycans)
                  - key proteoglycan molecule in the cartilage matrix and creates the osmotic properties necessary for cartilage
                          to resist compressive loads;
            - small proteoglycans (decorin (coats the outside of the collagen fibrils), biglycan, and fibromodulin);
    - link protein:
            - small glycoprotein serves to stabilize non-covalent association of the proteoglycan subunits with hyaluronic acid in aggregate;
    - protein core:
            - approximately 100 chondroitin sulfate   and 50 keratan sulfate chains are attached;

























Synthesis of chondrocytic keratan sulphate-containing proteoglycans by human chondrosarcoma cells in long-term cell culture.

Ultrastructural modifications of proteoglycans coincident with mineralization in local regions of rat growth plate.

Electron microscopic studies of cartilage proteoglycans: Direct evidence for the variable length of the chondroitin sulfate rich region of proteoglycan subunit core protein.
    JA Buckwalter and LC Rosenburg.   J. Biol Chem. Vol 257. 1982. p 9830-9839.

Assembly of newly synthesized proteoglycan and link protein into aggregates in cultures of chondrosarcoma chondrocytes.
    JH Kimura et al.   J. Biol Chemistry.   Vol 255. 1980. p 7134-7143.

























Original Text by Clifford R. Wheeless, III, MD.