Hyaluronic acid (HA) is a large molecule that consists of repeated sugar units and may be formed from several different cells. HA is found naturally in all organs of the body, in joints, in the eyes and in the skin. A person who weighs 70 kg has approx. 15 g hyaluronic acid in his body, about a third of which is metabolised every day. In the knee and joints HA has a lubricating and shock-absorbing function, and in softer tissue it gives structure and elasticity. HA’s unique ability to bind moisture also gives it many important tasks in the various transport systems of the body.More
HA is an enormously large molecule with a unique ability to bind water. The molecule forms a large volume, about 1,000 times its own volume, in which water molecules can move freely in and out of the “branches”.
The structure of HA can be compared, in simple terms, to the crown of a tree (the HA molecule) in which the birds (water molecules) can move in and out. When the molecule is at rest it builds a large, tangled nest and is almost jelly-like, but when it is exposed to forces, for example when a joint is set in motion, the nest is combed out and the layers of fluid can flow over each other.
The property that hyaluronic acid gives fluids is known as pseudoplasticity. Pseudoplasticity means that fluids become less viscous when they are exposed to shear forces. For example, synovial fluid owes its properties to hyaluronic acid and is therefore shock absorbing, yet lubricating in repeated movements. As hyaluronic acid is found naturally in the body its biocompatibility is very high and it is therefore suitable for medical uses.
The role of hyaluronic acid in the body
HA is found in many parts of the body, where its main tasks are to lubricate, cushion and retain moisture. Bohus BioTech manufactures HA-based products in three different areas, Ophthalmology, Aesthetics and Orthopedics, in which HA has the following functions:
In the eye HA is mainly found in the vitreous body, where it gives support to the retina and protects the eye from collapsing.
In the skin the main task of HA is to keep the skin moist in combination with other substances such as collagen and elastin. Besides this, HA makes the skin more flexible and is involved in forming new tissues by having an important role in the flow of water between tissues.
In the joints HA is found in cartilage and in synovial fluid. Cartilage acts as a sliding surface in our joints and HA is involved as one of the principal components here. HA also has the task of transporting nutrients and waste products to and from the joint cartilage. Thanks to the unique structure of hyaluronic acid, synovial fluid can act as both lubricant and shock absorber.
Besides being found in the human body, HA is also found in high concentrations in rooster combs. In order for HA to have the unique properties that make it suitable for medical uses it is necessary to manufacture a HA with a high molecular weight. Rooster combs contain high levels of a high-molecular weight hyaluronic acid that Bohus BioTech uses as a source for manufacture. The result is a product of high viscosity and thanks to the natural high molecular weight, the product does not need to be modified chemically after manufacture.
Chemical description of HA
Glycosaminoglycans (GAGs) is a general name for a number of similar molecules that are found in the plant and animal kingdom and have the function of giving tissue structure. Examples of GAG molecules are heparin and chondrotoin sulfate. HA is also a GAG and is one of the largest in the animal kingdom. HA is also a polysaccharide with a repeating disaccharide unit that consists of D-glucuronic acid and N-acetyl glucosamine with ß-(1-3) bonds that are linked to a protein. Each polysaccharide unit is cross-linked with ß-(1-4) bonds. HA has a molecular weight of between 5,000 and 20,000,000 Da. HA purified from synovial fluid has a molecular weight of approx. 3,500,000 Da.
Repeating disaccharide unit