Degradation of the Proteoglycans of Human Articular Cartilage by Reactive Oxygen Metabolites
The ability of articular cartilage to reversibly resist compression depends on the integrity of the proteoglycan aggregates, which are major components of the tissue. Each proteoglycan aggregate may have a total molecular weight of 200 × 106 and consists of a hyaluronic acid filament to which are attached up to 100 proteoglycan monomers in non-covalent interactions which are stabilized by the link glycoproteins. The proteoglycan monomer consists of a core protein of Mr 320,000, whose N-terminal region interacts with the link proteins and hyaluronic acid. To this core protein 130–200 anionic glycosaminoglycan chains are covalently bound. This high density of anionic groups draws water into the tissue until the osmotic swelling pressure is balanced by tension in the inelastic collagen network in which the proteoglycans are entrapped. The retention of intact proteoglycans in the tissue is essential for the high water content of the tissue, and it is the reversible redistribution of this bound water, under mechanical loading, which is responsible for the shock-absorbing properties of the tissue1.
KeywordsHyaluronic Acid Link Protein Reactive Oxygen Metabolite Human Articular Cartilage Cartilage Proteoglycan
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