HYALURONIC ACID. A ESSENTIAL ELEMENT
Hyaluronic acid is a biocompatible substance, a fundamental and ubiquitous of all tissues:
Connective (providing the link, support and nourishment of other tissues of various organs).
Epithelial (lining the inside and the outside of most of the bodily surfaces).
Neuronal (receive, transmit and process internal and external stimuli of the body).
Is present in the skin, synovial fluid overlying cartilage, in the upper and lower respiratory tract, in tendons, heart valves in the aortic walls, in the brain, the nucleus pulposus of the intervertebral discs, the vitreous humor of the eye and in the umbilical cord.
In the human body the medium concentration of hyaluronic acid is about 200 mg for kg of weight.
The hyaluronic acid, due to its unique physical and chemical characteristics and according to its molecular size, has various functions:
Filter against bacteria and micro organisms
Inflammatory and immunological responses adjustment
Transport of nutrients
Influence behavior, growth and cell differentiation
Scarring and tissue reconstruction
Hyaluronic acid is continuously metabolized and eliminated therefore it is imperative that the body continues to synthesize again.
HA decline during aging:
HA in a 20 year-old person 100% HA in a 30 year-old person 65% HA in a 50 year-old person 45% HA in a 65 year-old person 25%
The decrease of hyaluronic acid can be caused by many factors:
Hyaluronic acid is chemically classified as a glycosaminoglycan. The molecule is in fact formed by the repetition of long sequences of two simple sugars, glucuronic acid and N-acetylglucosamine. These substances are both negatively charged and when they join the strong repulsion gives rise to a linear molecule, flexible, highly polar and therefore with high solubility in water.
Thanks to this structure the hyaluronic acid is able to bind to a large number of water molecules forming a gel with a high degree of hydration.
The extreme length of the molecular chain, together with its high level of hydration allows hyaluronic acid to form a reticular structure able to act as a supporting scaffold, occupying a space decidedly superior to that which would be expected from its molecular weight and giving its typical viscoelastic characteristics.
Isolated the first time by Mayer and Palmer in 1934 as a constituent of vitreous body of eye in cattle, its simple polysaccharide structure was defined in 1951.
Until a few years ago, hyaluronic acid was extracted from natural sources such as rooster combs , bovine vitreous humor, or human umbilical cord.
This process had several disadvantages: poor standardization of molecular weights, the risk of viral infections, high costs. More recently these disadvantages have been largely abolished, and good results have been obtained thanks to new procedures.
Biotechnology is now able to refuel hyaluronic acid biopolymers with a molecular weight up to several million Daltons, more pure, more viscous, no protein content and not animal-derived.