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This Article Full Text Full Text (PDF) All Versions of this Article: 574/3/643    most recent jphysiol.2006.108100v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Scott, J. E. Articles by Stockwell, R. A. Search for Related Content PubMed PubMed Citation Articles by Scott, J. E. Articles by Stockwell, R. A. Related Collections Molecular and Genomic

¹ Chemical Morphology, Medical School, University of Manchester, Oxford Road, Manchester M13 9PT, UK
² Bourn House, South Knighton, Newton Abbott, Devon TQ12 6NP, UK

Cartilage ultrastructure is based on collagen fibrils tied together by proteoglycans (PGs). Interfibrillar orthogonal PG bridges (‘shape modules’) were located by electron histochemistry using Cupromeronic blue methodology. Their frequency and size, similar to those in tendon, cornea, etc., were compatible with biochemical estimates of tissue decoran (formerly decorin), the PG component of shape module bridges. Digestion by hyaluronanase and chondroitinase AC helped to identify aggrecan and decoran and exemplified the destruction of shape modular organization by glycan-splitting agents. The anionic glycosaminoglycan (AGAG) of decoran, dermochondan sulphate (DS, formerly dermatan sulphate), contains L-iduronate, an elastic sugar unit. Chondroitan, keratan (present in aggrecan) and hyaluronan are not similarly elastic but can participate in sliding-filament reversible deformability. Mechanical properties predicted for the interfibrillar bridges accord with anisotropic stress/strain responses of articular cartilage to compressive or tensile stresses. We propose that fluid from pericellular aggrecan-rich domains moves under pressure into the interterritorial fibrillar arrays against the elastic resistance of the shape modules, which return the fluid, post-compression, to its original position. Cartilage is tendon-like, with the addition of expansile aggrecan-rich reservoirs of aqueous shock absorber fluid. Rupture or loss of interfibrillar ties would allow expansile PG to force the collagenous matrix apart, imbibing water, increasing swelling and fissuring – characteristic manifestations of osteoarthrosis (OA), a joint disease of major economic importance. Decoran may be a primary target of the OA disease process.

(Received 21 February 2006; accepted after revision 27 March 2006; first published online 31 March 2006)
Corresponding author J. E. Scott: Chemical Morphology, Medical School, University of Manchester, Oxford Road, Manchester M13 9PT, UK. Email: john.e.scott{at}manchester.ac.uk

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