Glycosaminoglycans*, i.e., hyaluronan, keratan sulfate, chondroitin sulfate, and heparin/heparan sulfate are thought be space fillers, because they are localized in extracellular matrices. In general, ordinary pharmaceutical companies do not have expertise with technology of carbohydrates including glycosaminoglycans. Since this research area is considerably different from ones of proteins and nucleic acids, it is difficult to study carbohydrates. However, nowadays, research has shown that glycosaminoglycans have a wide variety of novel cell biological activities.
