Hyaluronic Acid (HA), also known as hyaluronan or hyaluronate, is a polysaccharide with a linear, non-branched structure, naturally present in living organisms – from bacteria to higher animals including human. Since it has maintained its structural features throughout evolution, which indicates its fundamental biological importance, hyaluronic acid is biocompatible and not immunogenic.
The molecule is made up of a repetitive sequence of two simple sugars, one called glucuronic acid and the other N-acetyl-glucosamine. These compounds are both negatively charged and when put together, they repel producing an exceptionally long, stretched out molecule organized into very long, multiple identical chains. It is important to note that the multiple biological roles of hyaluronic acid depend to a large degree on the size (molecular weight) of its chains.
Hyaluronic acid occurs in high concentrations in specific body locations in the dermis - both the deep underlying dermis, as well as the visible top layers of the epidermis) - and in the connective tisssue; in the joint cartilage and the synovial fluid that fills the joint cavity; in the tendons and ligaments; in the vitreous body of the eye, where it was initially discovered. Hyaluronic acid is metabolized with astonishing rapidity, and is replaced daily in the skin and joint fluid, thereby it is important to keep a proper balance between synthesis and degradation, to maintain hyaluronic acid homeostasis in the body.
With age, however, or in particular health conditions, the amount of hyaluronic acid decreases, and, as a result, signs of aging start to show, such as loss of elasticity and volume in the skin, leading to increased wrinkling, and joint problems, including osteoarthritis.