Abstract.
The primary function of articular cartilage to act as a self-renewing, low frictional material that can distribute load efficiently at joints is critically dependent upon the composition and organisation of the extracellular matrix. Aggrecan is a major component of the extracellular matrix, forming high molecular weight aggregates necessary for the hydration of cartilage and to meet its weight-bearing mechanical demands. Aggregate assembly is a highly ordered process requiring the formation of a ternary complex between aggrecan, link protein and hyaluronan. There is extensive age-associated heterogeneity in the structure and molecular stoichiometry of these components in adult human articular cartilage, resulting in diverse populations of complexes with a range of stabilities that have implications for cartilage mechanobiology and integrity. Recent findings have demonstrated that aggrecan can form ligands with other matrix proteins. These findings provide new insights into mechanisms for aggregate assembly and functional protein networks in different cartilage compartments with maturation and aging.
Key words. Aggrecan, cartilage, proteoglycan, aging, assembly, extracellular matrix, glycosaminoglycans, collagen network
Footnotes
Received 19 May 2005; received after revision 17 June 2005; accepted 23 June 2005