Alternative Names: Hyaluronan, hyaluronate.
The average 70-kg man has roughly 15gm of Hyaluronic Acid in his body, one-third of which is replaced every day.
Hyaluronic acid 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. It is an important component of articular cartilage, where it is present as a coat around each cell.
Hyaluronic acid 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 hyaluronic acid, and increase the rate of its degradation. The degradation products accumulate in the skin after UV exposure.
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 (i.e., corneal transplantation, cataract surgery, glaucoma surgery and surgery to repair retinal detachment). Other biomedical companies also produce brands of hyaluronan for ophthalmic surgery.
Hyaluronan may also be used postoperatively to induce tissue healing, notably after cataract surgery.
In some cancers, hyaluronan levels correlate well with malignancy and poor prognosis. Hyaluronan is thus often used as a tumor marker for prostate and breast cancer. It may also be used to monitor the progression of the disease.
Hyaluronan is a common ingredient in skin care products. 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. Hyaluronan injections temporarily smooth wrinkles by adding volume under the skin, with effects typically lasting for six months. People who have been on any blood medication with in the last five years should not inject this drug until the five year span is over. It is alleged that this drug is not suitable for use in elderly patients because it can cause memory loss, although there is no evidence in the literature of any negative cognitive effects attributable to hyaluronic acid injections.
The use of hyaluronic acid (HA) in osteoarthritis has been found to be effective in terms of relieving pain due to osteoarthritis (OA) of the knee and may potentially be a structure-modifying drug. Results of a study of 100 patients with OA of the knee who were treated with five weekly injections of intra-articular HA demonstrated significant improvement in terms of pain on walking at week five, which persisted for six months in two-thirds of patients. [Rheumatology 1999; 38: pp.602-607]
These treatments, called viscosupplementation, are administered as a course of injections into the knee joint and are believed to supplement the viscosity of the joint fluid, thereby lubricating the joint, cushioning the joint, and producing an analgesic effect. It has also been suggested that hyaluronan has positive biochemical effects on cartilage cells. However, some placebo controlled studies have cast doubt on the efficacy of hyaluronan injections, and hyaluronan is recommended primarily as a last alternative to surgery.