Hyaluronic acid is a naturally occurring biopolymer whose molecular structure is highly conserved between mammalian species. First described in 1934, it has since been used across a wide variety of medical fields as diverse as neurosurgery and cutaneous wound healing. Presently it has reached prominence in cosmetic practice where it is now the injectable dermal filler of choice for most surgeons.
Hyaluronic acid 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). The molecular weight (size) of hyaluronan in cartilage decreases with age, but the amount increases.
Hyaluronan is a polymer of disaccharides, themselves composed of D-glucuronic acid and D-N-acetylglucosamine, linked via alternating β-1,4 and β-1,3 glycosidic bonds. Hyaluronan can be 25,000 disaccharide repeats in length. Polymers of hyaluronan can range in size from 5,000 to 20,000,000 Da in vivo. The average molecular weight in human synovial fluid is 3−4 million Da, and hyaluronan purified from human umbilical cord is 3,140,000 Da.
Skin provides a mechanical barrier to the external environment and acts to prevent the ingress of infectious agents. Once injured, the tissues beneath are exposed to infection; therefore, rapid and effective healing is of crucial significance to reconstruct a barrier function. Skin wound healing is a complex process, and includes many interacting processes initiated by haemostasis and the release of platelet-derived factors.The following stages are inflammation, granulation tissue formation, reepithelization and remodeling. HA is likely to play a multifaceted role in mediation of these cellular and matrix events. The proposed roles of HA in this sequence of skin wound healing events are elucidated in details below.
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