Hyaluronic acid (HA) is a naturally occurring linear polysaccharide of the extracellular matrix of connective tissue, synovial fluid, and other tissues. It possesses various physiological and structural functions, which include cellular and extracellular interactions, interactions with growth factors and regulation of the osmotic pressure, and tissue lubrication. All these functions help in maintaining the structural and homeostatic integrity of the tissue.
Extensive studies on the chemical and physicochemical properties of HA and its physiological role in humans have proved that it is an ideal biomaterial for cosmetic, medical, and pharmaceutical applications.
HA is found in almost all vertebrate organs, but most abundantly in the extracellular matrix of soft connective tissues.
In the skin, it has a protective, structure stabilising and shock-absorbing role. The highest concentrations of HA are found in soft connective tissues (umbilical cord, synovial fluid, skin) and the lowest in blood serum.
Most cells of the body are capable of synthesising HA and synthesis take place in the cell membrane.