What Is Hyaluronan and Its Role in the Body?

Hyaluronan, also known as hyaluronic acid, is a substance naturally produced by the body and found in nearly every tissue. This ubiquity points to its varied and significant roles in maintaining the body’s structure and function. From cushioning joints to keeping skin hydrated, its presence is fundamental to numerous biological processes. This widespread distribution has also made it a focal point for innovations in medicine and cosmetics, where its inherent properties are leveraged for therapeutic and aesthetic purposes.

Defining Hyaluronan

Hyaluronan is classified as a glycosaminoglycan, which is a long, unbranched sugar chain. Its structure consists of repeating units of two specific sugars: D-glucuronic acid and N-acetyl-D-glucosamine. Unlike other similar molecules in the body, hyaluronan is not sulfated, meaning it does not have sulfur-containing groups attached to its chain.

A primary feature of hyaluronan is its ability to attract and hold vast amounts of water. This hygroscopic property is due to its large molecular weight and chemical structure, allowing it to form a viscous, gel-like substance when combined with water. This quality makes it an effective natural moisturizer and lubricant within the body.

This molecule is most concentrated in tissues requiring high levels of hydration and lubrication. It is a major component of the extracellular matrix, the substance surrounding cells that provides structural support. High amounts are found in the synovial fluid of joints, the vitreous humor of the eye, the skin, and the umbilical cord.

Essential Biological Roles

In joints, the high concentration of hyaluronan in synovial fluid gives it a thick, viscous quality. This allows the fluid to act as a lubricant, reducing friction between cartilage surfaces during movement, and as a shock absorber, cushioning the joint from impact. This viscoelasticity supports smooth and painless joint function.

Within the skin, hyaluronan is a primary molecule for maintaining hydration and volume. Its capacity to bind water helps keep the skin plump and elastic by retaining moisture in the dermal and epidermal layers. This supports the skin’s structure and helps prevent dehydration and the formation of wrinkles.

Hyaluronan also plays a part in the body’s healing processes. When tissue is injured, it helps create a hydrated matrix that facilitates the migration of cells involved in repair. It serves as a scaffold to guide these cells, supporting the formation of new tissue.

Beyond these roles, hyaluronan acts as a structural component, filling the spaces between cells to help organize the extracellular matrix. The molecule also participates in cell signaling, influencing cell behavior such as adhesion and motility by interacting with specific receptors on the cell surface.

Applications in Medicine and Cosmetics

In medicine, one of its most common applications is in the management of osteoarthritis, particularly in the knee. Intra-articular injections of hyaluronan supplement the natural synovial fluid, helping to restore lubrication and cushioning in the joint, thereby reducing pain and improving mobility.

During ophthalmic surgeries, such as cataract removal, a purified, high-viscosity hyaluronan solution is used as a viscoelastic agent. It protects delicate eye tissues, like the cornea, from surgical instruments and maintains space for the surgeon to work safely.

Hyaluronan is incorporated into advanced wound care products, such as gels and dressings, where it helps maintain a moist environment conducive to tissue regeneration and healing.

In the cosmetic industry, hyaluronan is used for non-surgical facial rejuvenation. As a dermal filler, it is injected into the skin to reduce the appearance of wrinkles, restore lost facial volume in areas like the cheeks, and augment the lips. Its gel-like nature provides immediate, visible results.

Topical skincare products, including serums and creams, frequently feature hyaluronan. When applied to the skin’s surface, it acts as a humectant, drawing moisture from the air to provide surface hydration. This helps to temporarily smooth and plump the skin, improving its texture and appearance.

Production and Safety Aspects

The hyaluronan used in commercial products is sourced through two methods. Historically, it was extracted from animal tissues, with rooster combs being a rich source. This method posed risks of allergic reactions and had limitations in purity and consistency.

Today, the vast majority of commercial hyaluronan is produced through microbial fermentation. In this process, specific strains of bacteria, often from the Streptococcus genus, are cultured to produce hyaluronan. This fermentation method allows for precise control over the molecular weight and purity of the final product, resulting in a highly consistent and safe material chemically identical to that found in the body.

Because hyaluronan is a natural component of the body, products derived from it are very well-tolerated. Side effects are mild and related to the administration method, not the substance itself. For instance, injections for joint therapy or cosmetic fillers can cause temporary redness, swelling, or bruising at the injection site.

Allergic reactions are rare, especially with bacterially derived hyaluronan. A product’s safety can be influenced by its purity and whether it has been chemically modified, a process known as cross-linking, which is often done to make dermal fillers last longer. Individual patient factors can also play a role in the response to treatment.