Hyaluronic acid, a major constituent of animal tissues, also called hyaluronan or hyaluronate (HA), is considered an important glycosaminoglycans due to its varied physiological functions.
Hyaluronic acid has good biocompatibility, biodegradability, high viscoelasticity, and nonimmunogenicity, and can be combined with specific receptor on the cell surface.
HA has multiple important functions in the human body, due to its properties such as bio-compatibility, lubricity and hydrophilicity, it is widely applied in the biomedical, food, health and cosmetic fields.
There are applications and emerging trends of Hyaluronic Acid in tissue engineering and in osteoarthritis treatment. Hyaluronic acid (HA) is a naturally occurring biodegradable polymer with a variety of applications in medicine including scaffolding for tissue engineering, and viscosupplementation for osteoarthritis treatment. HA is available in most connective tissues in body fluids such as synovial fluid and the vitreous humor of the eye. HA is responsible for several structural properties of tissues as a component of extracellular matrix and is involved in cellular signaling. Degradation of HA is a step-wise process that can occur via enzymatic or non-enzymatic reactions. A reduction in HA mass or molecular weight via degradation or slowing of synthesis affects physical and chemical properties such as tissue volume, viscosity, and elasticity.
HA can include several thousand sugar molecules in the backbone. HA is a polyanion that can self-associate and that can also bind to water molecules (when not bound to other molecules) giving it a stiff, viscous quality similar to gelatin.
Hyaluronic acid is one of the major elements in the extracellular matrix of vertebrate tissues. It is available in almost all body fluids and tissues, such as the synovial fluid, the vitreous humor of the eye, and hyaline cartilage. This biopolymer functions as a scaffold, binding other matrix molecules including aggrecan. It is also involved in several important biological functions, such as regulation of cell adhesion and cell motility, manipulation of cell differentiation and proliferation, and providing mechanical properties to tissues. Several cell surface receptors have been shown to interact with HA influencing cellular processes including morphogenesis, wound repair, inflammation, and metastasis. Moreover, HA is responsible for providing the viscoelasticity of some biological fluids (synovial fluid and vitreous humor of the eye) and controlling tissue hydration and water transport. In addition, HA has been found during embryonic development in the umbilical cord, suggesting materials composed of HA may persuade favorable conditions for tissue regeneration and growth.
Examples of body tissues/fluids that contain HA.
|Tissue or body fluid||Concentration (μg/g; μg/mL)||Remarks|
|Umbilical cord||4100||High molecular weight HA.|
|Joint (synovial) fluid||1400–3600||Decreasing HA concentration occurs due to increasing the synovial fluid volume under inflammatory conditions.|
|Vitreous body||140–500||During tissue maturation, HA concentration increases.|
|Cartilage||-||HA works as a scaffold for binding other matrix molecules such as aggrecan.|
|Dermis||200–500||HA is used as a “rejuvenating” agent in cosmetic dermatology.|
|Epidermis||100||High HA concentration was observed around cells that synthesized dermis.|
|Thoracic lymph||0.2–50||HA molecular weight affects inflammatory response and cell binding.|
HA's characteristics including its consistency, biocompatibility, and hydrophilicity have made it an excellent moisturizer in cosmetic dermatology and skin-care products. Moreover, its unique viscoelasticity and limited immunogenicity have led to its use in several biomedical applications such as viscosupplementation in osteoarthritis treatment, as an aid in eye surgery, and for wound regeneration.
HA is ideal for lubrication in biomedical applications.
Hyaluronic acid performs several structural tasks in the extracellular matrix as it binds with cells and other biological components through specific and non-specific interactions. Several extracellular matrix proteins are stabilized upon binding to HA.
HA can be a key player in the activation or suppression of inflammation. Over the early steps of inflammation, HA participates in the improvement of cell infiltration. The free radical scavenging and antioxidant characteristics of HA influence suppression of the inflammatory response. In addition, HA may also operate as a negative feedback loop in inflammatory activation. Cell proliferation is an important phase of the tissue repair process after damage (e.g. by inflammation). HA is necessary for fibroblast detachment from the extracellular matrix and mitosis. HA has a mitogenic influence directly on cells however the relief of detachment permits mitosis to take place and therefore HA has a function in cell proliferation indirectly. In the early stages of wound repair when increased HA synthesis takes place, cell migration is promoted.
Hyaluronic acid (HA), also named hyaluronan, is a high molecular weight (105–107 Da) naturally occurring biodegradable polymer.
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