Hyaluronic acid Physiological function

Cell migration

Cell migration is critical for the formation of granulation tissue.The early stages of granulation tissue are dominated by HA-rich extracellular matrix,which is thought to be a favorable environment for cell migration into this temporary wound matrix.HA provides an open hydrated matrix that facilitates cell migration,whereas in the latter case the directed migration and control of the relevant cellular machinery is mediated through specific cellular interactions between HA and cell surface HA receptors of.It forms associations with various protein kinases associated with cell motility,such as extracellular signal-regulated kinases,focal adhesion kinases,and other non-receptor tyrosine kinases.During fetal development,the migratory pathway of neural crest cell migration is enriched in HA. HA is closely related to the process of cell migration in the granulation tissue matrix, and studies have shown that cell motility can be at least partially inhibited by HA degradation or blocking HA receptor occupancy.By powering cells,HA synthesis has also been shown to be involved in cell migration.Basically,HA is synthesized at the plasma membrane and released directly into the extracellular environment.This may contribute to a hydrated microenvironment at the site of synthesis and is critical for cell migration by promoting cell detachment.

Skin healing 

HA plays an important role in normal epidermis.HA also has important functions in the re-epithelialization process due to several properties of HA.These include being a component of the extracellular matrix of basal keratinocytes, which are the major constituents of the epidermis;its free radical scavenging function,and its role in keratinocyte proliferation and migration.In normal skin, the concentration of HA is relatively high in the basal layer of the epidermis,where proliferating keratinocytes are located.CD44 is juxtaposed with HA in the basal layer of the epidermis,and additionally it has been shown to be preferentially expressed on the plasma membrane facing the HA-rich matrix pocket.Maintaining the extracellular space and providing an open and hydrated structure for the passage of nutrients are the main functions of HA in the epidermis.One report found that HA content was higher than that of retinoic acid (vitamin A).The proposed effects of retinoic acid on skin photodamage and photoaging may be related, at least in part, to increased skin HA content, resulting in increased tissue hydration.It has been suggested that the free radical scavenging properties of HA help protect against solar radiation, supporting the role of CD44 as a receptor for HA in the epidermis.Epidermal HA also acts as a manipulator during keratinocyte proliferation,which is essential for normal epidermal function as well as re-epithelialization for tissue repair.During wound healing,HA is expressed at the wound margin, in the connective tissue matrix, and is paired with CD44 expression in migrating keratinocytes

Medical uses

Hyaluronic acid is FDA-approved for the treatment of knee osteoarthritis by intra-articular injection.A 2012 review indicated that studies supporting this use were mostly of poor quality,generally lacking significant benefit,and that intra-articular injections of HA may result in adverse effects.A 2020 meta-analysis found that intra-articular injections of high molecular weight HA improved pain and function in patients with knee osteoarthritis.Hyaluronic acid has been used in various formulations to create artificial tears for the treatment of dry eye.Hyaluronic acid is a common ingredient in skin care products.Hyaluronic acid is used as a dermal filler in cosmetic surgery.It is usually injected with a classic sharp hypodermic needle or a microcannula.Several studies have shown that the use of microcannulas can significantly reduce vascular embolism during injection.Currently, hyaluronic acid is often used as a soft tissue filler because of its biocompatibility and possible reversibility using hyaluronidase Complications include severed nerve and microvascular, pain and bruises.Some side effects may also manifest as erythema,itching, and vascular occlusion; vascular occlusion is the most worrisome side effect, as patients may experience skin necrosis and even blindness.Hyaluronic acid fillers have been associated with granulomatous foreign body reactions in some cases.