What is hyaluronic acid?

Hyaluronic acid was first discovered in the 70s in the vitreous humor of eyes. It has been given this name as “hyalos” means “glassy” and “uronic” because it is rich in glucuronic acid. Hyaluronic acid is present in the synovial fluid (joint) and is the main molecule of the extracellular matrix of the skin.

How is it produced in our body?
Hyaluronic acid is a polymer (polymer = big molecule made of repeated smaller molecules), composed of two sugars that our cells produce throughout their lives (N-acetyl-glucosamine-6-phosphate and glucuronic acid). Our cells assemble these two sugars like a pearl necklace alternating each of these sugar molecules to produce hyaluronic acid.

What happens to hyaluronic acid upon aging?
Hyaluronic acid is very sensitive to free radicals, and hydrolyzing enzymes (hyaluronidase). An estimated one third of hyaluronic acid in our body is produced and degraded every day. As we age the production rate becomes lower than the rate of degradation, partially explaining some of the problems of skin sagging and painful joints. In conditions, stimulating the abnormal production of free radicals in our skin (such as UVs exposure, pollutants, chemical stresses), hyaluronic acid degrades even more quickly, leading to the appearance of premature signs of aging.

What are the different grades of hyaluronic acid used in cosmetic products?
There are two generations of hyaluronic acid:
     – High molecular weight hyaluronic acid is used in aesthetic medicine (sub-dermal injections) in its natural form or reticulated one, to fill wrinkles. In cosmetics, this grade of hyaluronic acid is used as a moisturizer because it has the main property of retaining water on the skin surface. It is also used to modify the viscosity of formula and create a nice sensory feeling upon application on skin. This grade of hyaluronic acid has no biological activity on the skin.
     – Fragmented hyaluronic acid (low molecular weight), is madeup of small pieces of high molecular weight hyaluronic acid. This grade is mainly used in cosmetics, as these pieces have been shown to activate some biological pathways, leading to anti-aging effects.

Can we reactivate the synthesis of hyaluronic acid in aged skins?
Some molecules like retinol are known to reactivate skin’s hyaluronic acid synthesis. However the use of retinol is limited for two reasons: it is very unstable in formula (it requires airless formulation), and it is very irritating on the skin.

New generations of cosmetic products that have been launched over the past years contain a « third generation hyaluronic acid ». This active ingredient is one of the two sugars that our cells need to make hyaluronic acid, and that they cannot do any more once they get older. Such products are able to re-plump, firm and regenerate the skin rapidly. Some US press journalist even called it the « needle free HA », as comparison to injectable HA in the esthetic medicine. You will find it under the name DISODIUM ACETYL GLUCOSAMINE PHOSPHATE on the composition list of your cosmetic products.