Articular cartilage is a highly specialized tissue, composed by cells, the chondrocytes, and macromolecules, such as collagen and proteoglicans. Collagen is a fibrilar protein responsible for the tissue resistance. Proteoglicans have a spring-like biologic function, being responsible for compressibility of cartilage. The complex interaction between these proteins warrants the elasticity of articular cartilage. These specific cartilage characteristics are essential to amortize the shock to which the diarthrodial joints are submitted, without excess of energy expense, because it is an avascular tissue. It is observed in osteoarthritis an imbalance between extracellular matrix components production and the destruction done by matrix metalloproteinases, promoting cartilage degradation. In the early osteoarthritis process, proteoglicans fragments are lost into synovial fluid, types II and VI collagen increases, atypical types I and III collagen appears and type IX collagen decreases. These biochemical alterations modify the specific characteristics of cartilage and, consequently, the articular function. The disease progression leads to a high decrease of proteins, including also type XI collagen, located deeply into the heterotypical cartilage fibril, contributing to bone exhibition. Until now, the osteoarthritis treatment is based on the use of drugs to relief the pain and/or inflammation, without protective effect on cartilage degradation. Regarding this aspect, the synthetic metalloproteinases inhibitors associated with chondroprotector drugs may reduce the cartilage degradation and can represent a future advance treatment in osteoarthritis.
osteoarthritis; cartilage; collagen; metalloproteinases
