ABSTRACT
Hyaluronan (HA) is a ubiquitous glycosaminoglycan found in almost all tissues. HA was first characterized from the vitreus of the eye (1) and shown to contain a hexuronic acid, an amino sugar, and acetyl groups with no sulfoester content. HA was subsequently isolated from umbilical cord, and glucuronic acid and glucosamine sugar constituents were identified (2). The actual linkages of the repeating disaccharide motif (-β-1,4-glucuronic acid-β1,3-N-acetylglucosamine-)n was described in 1954 (3). The number of repeat disaccharides can approach 30,000 (a molecular mass of 10 106 daltons) in tissues such as synovial fluid. In the lung, HA can exist as a soluble polymer or complexed with proteoglycans. In the lung, the major proteoglycan with HA side chains is versican. The polyionic nature of HA polymers results in an avidity for water, and HA has been suggested to have a role in regulating edema formation and solute transport in the lung interstitium (4). In addition to regulating physiological processes in the normal lung, HA undergoes dynamic regulation under conditions of tissue injury and inflammation. The purpose of this review is to discuss the emerging roles of HA in lung injury, inflammation, and repair.
