Hyaluronic Acid

Dermal Fillers

Dermal fillers are a products injected under the skin to replace or augment volume in a way that aims to improve the aesthetics of the face.

There are hundreds of types, but the market is dominated by hyaluronic acid fillers, which have by far the best safety profile.

Common brands are Juvederm, Restylane, Boletero. They are also used in other fields of medicine, including orthopaedics to aid arthritic joints and in eye surgery.

What is Hyaluronic acid (HA)?

HA -Alternating units of 1,4 linked N-Acetylglucosamine and glucuronic acid Hyaluronic acid is a ubiquitous carbohydrate (or more accurately a mucopolysaccharides) found in the human body in interstitial fluid, the vitreous humour of the eye, and in synovial fluid to name a few.

It consists of a repeating units N-Acetylglucosamine and glucuronic acid and can be extremely long. In the body it is continuously made and broken down, with a half life of just 24 to 36 hours in the skin. As we age production slows, but the half life remains the same, so total quantity is reduced. This forms part of the reason there is a decrease in skin volume.

Cross Linked Hyaluronic Acids

Because HA in the body has such a short half life, it was needed to modify the molecule so that it would be commercially viable. Juvederm is cross linked with a molecule called (BDDE 1,4-butanediol diglycidyl ether). These links slow the natural metabolism of the molecule to take up to 12 months. Mechanism of action The HA molecule has some very unusual properties- a high degree of elasticity and excellent lubricating properties. It easily becomes quickly integrated with native collagen and elastin molecules, but by far its biggest strength is its ability to hold 1000 times its own weight in water.

The result is a product that feels natural, (because it’s a soft gel), lasts 6 to 12 months (because it’s cross linked), stays where you put it (because it integrates with native tissue), and is reversible if required (using hyluronidase to break up the long HA chains).

All in all, the HA molecule is very close to the ‘ideal’ filler”.

An interesting extra benefit recently discovered is that it stretched fibroblasts, the cells in the skin that make collagen, in a way that causes them to create new collagen. This new, natural collagen then would contribute to the reduction of the appearance of creases and wrinkles. The study also shows that the product seems to inhibit the breakdown of existing collagen.