The collagens of articular cartilage.
Articular cartilage contains at least five genetically distinct types of collagen. Types II, IX, and XI are cartilage-specific and are cross-linked together in a copolymeric network that forms the extracellular framework of the tissue. Fibrils of type II collagen provide the basic architecture. Type XI, a quantitatively minor fibril-forming collagen, is probably copolymerized with type II collagen in the matrix. Type IX collagen accounts for approximately 1% of the collagenous protein in adult articular cartilage and its molecules exist in the tissue covalently linked to the surface of type II collagen fibrils. Its suspected functions include regulating fibril diameters and mediating fibril-fibril and fibril-proteoglycan interactions. Stromelysin, a matrix metalloproteinase, was recently shown to degrade type IX collagen. This action may cause the collagen network swelling seen in articular cartilage in early experimental osteoarthritis, (OA). Collagen type X is restricted to the underlying calcified zone of articular cartilage, a zone that exhibits active remodeling in joints with OA. Degradation products of the various cartilage collagens show promise as molecular markers of joint disease.
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Department of Orthopaedics, University of Washington, Seattle 98195.
D000595:Amino Acid Sequence; D000818:Animals; D015415:Biomarkers; D002358:Cartilage, Articular / Q000378:metabolism*; D003094:Collagen / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007592:Joint Diseases / Q000378:metabolism; D019278:Matrix Metalloproteinase 3; D008666:Metalloendopeptidases / Q000494:pharmacology; D008969:Molecular Sequence Data; D009154:Mutation; D010003:Osteoarthritis / Q000235:genetics / Q000378:metabolism
D015415:Biomarkers; D003094:Collagen; D008666:Metalloendopeptidases; D019278:Matrix Metalloproteinase 3