Emerging Frontiers in cartilage and chondrocyte biology.

Articular cartilage is a uniquely ordered tissue that is designed to resist compression and redistribute load, but is poorly equipped for self-repair. The chondrocyte is the only resident cell type, responsible for maintaining a specialised and extensive matrix that is avascular and lacks innervation. These attributes, as well as the slow turnover rate of aggrecan and type II collagen in mature articular cartilage, present a considerable challenge to the tissue engineer. Similarly, those attempting to halt the progression of cartilage erosion must contend with these unusual characteristics. This review explores the gaps in our knowledge of cartilage biology and pathology, including what is known about the relative contribution of collagenases and aggrecanases to cartilage degradation, the need to regulate the chondrocytic phenotype and the putative role of chondrocyte hypertrophy in the pathogenesis of degenerative and rheumatic joint disease. Recent advances in cartilage tissue engineering are also reviewed.