Hyaluronic acid has a dual mechanism of action: structural, thanks to its physico-chemical characteristics, and biological.
The hyaluronic acid chain length – hence, its molecular weight, which varies in the different tissues, is of great importance in the balance of its structural and biological activities, and this variability can impact on the molecule’s therapeutic applications. Not all hyaluronic acids are the same as concerns properties and uses.
For instance, hyaluronic acid exists naturally in the fluid that bathe the joints (synovial fluid), where it endows synovial fluid with its viscoelastic properties and acts like a shock absorber, as well as a lubricant in the movable parts of the joint; in addition, it provides protection and carries nutrients to the cartilage, while also removing waste from the joint capsule.
Moreover, by interacting with specific cell surface receptors, namely CD44, I-CAM 1, RHAMM, and TL-R, hyaluronic acid mediates inflammatory response and pain.
To properly balance this dual effect exerted in the joint - viscoelastic and biological - which is in turn dependent on the molecular weight, it is of primary importance to use a hyaluronic acid preparation specifically designed for the management of the various stages of osteoarthritis, or acute and chronic cartilage damage. With mild or moderate osteoarthritis, hyaluronic acid shall have a (optimal) molecular weight of appropriate range, to exert its biological effects on the articular cartilage; patients with severe osteoarthritis, where the integrity of the articular cartilage is significantly compromised and therefore, the biological activity is less valued, will benefit from a hyaluronic acid preparation with adequate visco-elastic characteristics.
In the skin, hyaluronic acid with a lower molecular weight is preferred: by interacting with specific receptors, HA plays a fundamental role in the migration and proliferation of specific cell types – the fibroblasts and thekeratinocytes, two processes that occur during repair of both acute and chronic skin lesions. In addition, recent scientific evidence has shown how hyaluronic acid is able to promote innate defense responses against microbial contamination, by improving the release of an endogenous peptide that acts like a local antibiotic (beta Defensin).