Hyaluronic acid from a chemical point of view
Hyaluronic acid is a glycosaminoglycan (GAG), a large molecule made up of many repeated disaccharide units. GAGs are negatively charged: this property gives them a great capacity for hydration. Hyaluronic acid is found free in the extracellular matrix (that is, in the area outside the cells), or it can be bound by link proteins to proteoglycans, other molecules present in the amorphous substance, forming even larger molecules.
Where is it found?
As already mentioned, hyaluronic acid is found in loose connective tissue, in the dermis, in synovial fluid, in the vitreous humour, in the umbilical cord and in epithelia. It was in the vitreous humour, the fluid inside the eyeball, that it was first discovered. It is also present in animal tissues and in some types of bacteria.
What is its function?
Its main function is support, hydration and lubrication: the latter in particular is important for the joints. The synovial fluid present in the joints (e.g. the knee) acts as a cushion and lubricant, allowing us to move with ease. When synovial fluid is scarce in certain joint conditions, walking and even the simplest movements become very painful, because the two ends of the joint rub against each other.
In the dermis, on the other hand, hyaluronic acid essentially makes the skin more elastic and maintains its tone and hydration.
With ageing, less and less hyaluronic acid is produced. This is why wrinkles begin to appear, joints become less mobile and various other disorders arise. Hyaluronic acid also protects against pathogenic substances and organisms. There are bacteria that have enzymes, called hyaluronidases, which destroy hyaluronic acid in order to infiltrate our body.
How is it produced?
Today hyaluronic acid is produced by bacterial fermentation using recombinant DNA technology. Previously, however, hyaluronic acid was of animal origin: it was found, for example, in rooster combs.
But what are the uses of hyaluronic acid?
Given its functions, and the aesthetic and clinical problems that arise from a deficiency of it, the question is how, and whether, to supplement it.
For wrinkles, for example, fillers are used: injections of hyaluronic acid that fill the dermis beneath the wrinkle, smoothing it out. Fillers can also be used to plump thin lips or to fill scars. These minor procedures have the drawback of having to be repeated periodically, because the hyaluronic acid is reabsorbed.
In surgery and medicine, it is used to speed up the healing of wounds.
Hyaluronic acid is also present in many moisturising and anti-ageing creams. In this case it is worth knowing that the effects are much milder than those of a filler.
Hyaluronic acid infiltrations can also be used to combat joint problems, first and foremost osteoarthritis. The infiltrations reduce inflammation and restore the cushion inside the joints that has been lost.
There are also hyaluronic acid supplements that are taken orally and are intended to help the body in the endogenous production of this GAG. The substance is first digested, then the individual compounds are used to produce it inside the body’s cells.
