Hyaluronan (Molecule of the Month for April 2008)
Hyaluronic acid, Restylane, Macrolane, Healon
Hyaluronan (also called hyaluronic acid or hyaluronate) is a glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues. It is one of the chief components of the extracellular matrix, contributes significantly to cell proliferation and migration, and may also be involved in the progression of some malignant tumors. The average 70-kg man has roughly 15 grams of hyaluronan in his body, one-third of which is turned over (degraded and synthesised) every day. Hyaluronan is a common ingredient in skin care product, and the branded version Restylane is used as injections to temporarily smooth wrinkles by adding volume under the skin or the brand Macrolane to increase breast size by adding volume using a natural tissue chemical.
Hyaluronan is a polymer of disaccharides, themselves composed of D-glucuronic acid and D-N-acetylglucosamine, linked together via alternating β-1,4 and β-1,3 glycosidic bonds. Hyaluronan can be 25,000 disaccharide repeats in length. Hyaluronan is an important component of articular cartilage, where it is present as a coat around each cell (chondrocyte). When aggrecan monomers bind to hyaluronan in the presence of link protein, large highly negatively-charged aggregates form. These aggregates imbibe water and are responsible for the resilience of cartilage (its resistance to compression). Hyaluronan is also a major component of skin, where it is involved in tissue repair. When skin is excessively exposed to UVB rays, it becomes inflamed (sunburn) and the cells in the dermis stop producing as much hyaluronan, and increase the rate of its degradation. Hyaluronan degradation products also accumulate in the skin after UV exposure. Hyaluronan also contributes to tissue hydrodynamics, movement and proliferation of cells, and participates in a number of cell surface receptor interactions.
Hyaluronan is naturally found in many tissues of the body, such as skin, cartilage, and the vitreous humor. It is therefore well suited to biomedical applications targeting these tissues. The first hyaluronan biomedical product, Healon, was developed in the 1970s and 1980s by Pharmacia, and is approved for use in eye surgery. In 2003 the FDA approved hyaluronan injections for filling soft tissue defects such as facial wrinkles. Restylane is a common trade name for the product, injections of Restylane temporarily smooth wrinkles by adding volume under the skin, with effects typically lasting for six months, it is also used to give volume to lips. More recently, Macrolane, another trade name has been used as a non-surgical body shaping treatment that can naturally regenerate body contours. This can be used for large volume restoration and shaping of body surfaces, for example, calves and buttocks. Macrolane can also even out discrepancies in the skin surface, for example those caused by liposuction. In 2008, Macrolane has started to be used for breast shaping, and is aimed to be used for women whom have asymmetry, loss of volume as a result of breast feeding or weight loss, or under-developed breasts. Marketing suggests it is suitable for women to increase by a cup size without the need for surgery. Of course, the body naturally processes hyaluronan, so shaping only last for 12-18 months and top-ups would be required to retain shape or smooth skin.
Formal Chemical Name (IUPAC)
Update by Karl Harrison
(Molecule of the Month for April 2008 )