Cartilage aggrecan. Biosynthesis, degradation and osteoarthritis.

The main "shock absorbing" molecule in cartilage is the proteoglycan, aggrecan, which is trapped within a meshwork of collagen fibrils. Articular cartilage damage in osteoarthritis is associated with damage to the aggrecan protein moiety. This results in abnormal loss of aggrecan which in turn increases the propensity of the joint surface to be damaged. Presently, the treatment for arthritis, pain-relieving drugs, affects the symptoms. End-stage osteoarthritis requires joint replacement surgery. To a certain extent, both the degradation and the repair of cartilage can be understood at the level of the biochemistry of cartilage matrix and the biology of the chondrocyte.