Hyaluronic acid (hyaluronan) is one of the main polymers of the extracellular matrix in different tissues. It traps the water molecules and maintains the proper viscosity of mucosa, synovial fluid and aqueous humour. It is also in a large extent responsible for the skin elasticity. The length of one hyaluronan molecule can be up to 10 micrometers, which is only 7-8 times shorter than a width of a human hair. Molecules of this polymer make a network that traps other compounds in the extracellular matrix. Hyaluronan traps approximately 1000 times its weight in water . Human body contains about 15 grams of hyaluronic acid. 5 grams turn over every day . Concentration and length of hyaluronan affect the angiogenesis, regeneration of wounds, the work of white blood cells and even the tumor metastasis . Senescence cause partial degradation of hyaluronan and it is one of the reasons of skin folds and wrinkles formation. Some factors such as cigarette smoke can enhance this process . Hyaluronic acid has been discovered by Karl Mayer and John Palmer in 1934. The isolated this compound from the eye of a cow . The first attempts of commercial usage of hyaluronan took place 8 years later — the polymer was used to substitute egg white in bakery. The first medical application of hyaluronan for humans was as a vitreous substitution/replacement during eye surgery in the late 1950s . Now hyaluronic acid is widely used in the therapy of osteoarthritis, regeneration medicine and rejuvenation cosmetological procedures [7, 8, 9].
Hyaluronic acid is a polysaccharide. It may include up to 25000 monomer residues. The enzymes that produce this polymer are called hyaluronan synthases (HAS). These are the cell membrane integrated proteins [10, 11, 12]. They use activated nucleotide sugars (UDP-glucuronic acid and UDP-N-acetylglucosamine) to add glucuronic acid and N-acetylglucosamine to the growing polymer linear chain. The necessity of hyaluronan synthesis to tumor metastasis makes HAS a possible target for cancer therapy . On the other hand, hyaluronic acid may become a basis of the nanocarriers for the targeted drug delivery . Hyaluronan injections do not cause a significant immune response or allergic reactions which is a ponderable advantage in osteoarthritis therapy and use of the hyaluronic acid as a cosmetic skin filler. Hyaluronan in industry was traditionally isolated from the rooster combs but now many laboratories and companies are trying to find out how to produce hyaluronic acid using genetically modified microorganisms [14, 15, 16].
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