Structure and regulation of articular cartilage proteoglycan expression]

Beyond aggrecan, the major proteoglycan present in articular cartilage that confers resistance to compressive load and viscoelasticity to the tissue, other proteoglycan families have been described in cartilage. Among them, decorin, biglycan and fibromodulin which belong to the small leucine-rich proteoglycans family bind to matrix components, specially to collagen fibrils and thus regulate fibrillogenesis in cartilage and matrix integrity. These small proteoglycans can also interact with TGF-beta and modulate its bioavailability and stability. The third family is composed by cell surface proteoglycans as syndecans, glypican-1 and betaglycan. These molecules interact with various components of cell environment (growth factors, proteases, matrix components, etc.) and mediate numerous cell functions. Some modifications of one of these proteoglycan expression occur during degenerative pathologies and may lead to alteration of the functional properties of the tissue as well as variations in growth factor bioavailability. These factors are involved in the attempt of cartilage repair initiated by chondrocytes in the early stages of osteoarthritis.