Hyaluronic acid (HA), a polymer with elastic properties, is a polysaccharide formed from N-acetyl-D-glucosamine and glucuronic acid. HA belongs to a group of chemicals called glycosaminoglycans (GAGs). The activity of a specific form or polymer of HA depends on the size the molecule. HA forms an aggregation center for a large molecule of chondroitin sulfate proteoglycan to maintain cartilage structure.
HA is found in most body fluids and tissues and is most concentrated in the extracellular material of soft connective tissues and in joint fluid.
The synovial fluid increases in joints during inflammation so that the concentration of HA decreases. HA maintains lubrication of joints and acts as a shock absorber when the HA is at a high level in the synovial fluid. There is a progressive loss of HA in the joint spaces of patients with rheumatoid arthritis and joint injections of HA are used in arthritic joints.
About one-half of the HA of the human body is in the skin, which immobilizes water and maintains the compressibility of the skin. HA is a scavenger of free radicals produced by the ultraviolet (UV) light of the sun on the skin. UV light can damage the genetic material of skin cells by creating free radicals. Topical high molecular weight HA has been shown to improve healing in fresh wounds, promote leg circulatory ulcer healing and is helpful with chronic wounds.
HA is present in some bacteria, but is absent in fungi, plants and insects. The highest concentration is found in rooster combs, from which most of the HA used for medical injections is derived. HA is used in eye surgery and is in the human vitreous of the eye.
HA serum levels increase in the elderly in rheumatoid arthritis and liver cirrhosis. It is used as a diagnostic marker in cancer, rheumatoid arthritis and liver disease. HA is a major large molecule in the eye and has many uses in ophthalmology.
CONCLUSION: Hyaluronic acid is an important structural component of different tissues of the body. Among other properties, HA is anti-inflammatory. The properties depend on the molecular weight. Most uses discussed involve injections or external use.
NOTE: The benefit of oral HA use is controversial in regard to absorption. Glucosamine and N-acetyl glucosamine are necessary for the production of HA by the body.
HA belongs to a class of chemicals called GAGs. Chondroitin sulfate is also a GAG.
Hyaluronic acid can be tried for dry eye syndrome and for Sjogren’s syndrome.