Age-associated changes in cartilage matrix - Implications for tissue repair

The structure of the extracellular matrix of articular cartilage varies con siderably with age. These changes are attributable to variations in molecul ar abundance and structure, and they can affect all the matrix components, but none more so than the proteoglycans. Some of these changes are attribut able to variations in synthesis whereas others are attributable to variatio ns in degradation, some of the changes occur during juvenile development wh ereas others occur throughout life, and some of the changes are beneficial to cartilage function whereas others are detrimental. These variations resu lt in a cartilage that not only changes in its phenotype with age, but also in one whose functional properties are changing continuously throughout li fe. In a similar manner, the cartilage formed during repair also may show c onsiderable variation in structure and function, depending on whether tissu e is being replaced or regenerated and whether mature or immature cells are being used. Because all cartilage is not ceated equal, different repair te chniques may not be equally efficacious.