Hyaluronan, a truly "youthful" polysaccharide. Its medical applications

Hyaluronan (hyaluronic acid, HA) is a ubiquitous linear polysaccharide endowed with some exceptional physicochemical properties such as strong hydration and viscoelasticity that depend on the size of the molecule. It plays a variety of important physiological roles in tissue hydration and mechanical protection, for example in the umbilical cord, skin and most other tissues. Since its large scale preparation and the invention by E.A. Balazs of the preparation of its non-inflammatory fraction (NIF-NaHA), there have been several important medical and cosmetic applications, most notably of viscosurgery for eye operation, intra-articular injections for osteoarthritis and also for wrinkle filling on the face, as well as for drug administration. Its concentration in tissues is decreasing with age, source of loss of function and structure of tissues. The purpose of this review is to present a succinct overview of the essential properties of hyaluronan and its medical and esthetic applications.