Heteropolysaccharides are high molecular weight carbohydrate polymers composed of more than one type of monosaccharide unit. They are mainly glycosaminoglycans (GAGs) that contain an amino sugar and uronic acid. The major GAGs are hyaluronic acid, chondroitin sulfate, dermatan sulfate, keratan sulfate, and heparin. They play important roles in tissue structure, hydration, lubrication and cell signaling. GAGs are isolated from tissues using ion exchange and gel permeation chromatography.