Background
An understanding of the mechanisms involved in cartilage degradation that occur in rheumatoid arthritis and osteoarthritis is essential for the development of treatments to block disease progression. Culturing chondrocytes to synthesize a cartilage matrix would ideally provide a cartilage matrix of consistent composition that would reproducibly respond to different stimuli. When cultured in monolayers, chondrocytes convert to a fibroblastic morphology and gradually lose their native phenotype, no longer able to synthesize type II collagen and aggrecan. However, when chondrocytes are cultured at a high density in the presence of growth factors, the chondrocytes regain their native phenotype and native round morphology [1].