Hyaluronan

Hyaluronan, also known as hyaluronic acid or hyaluronate, is a naturally occurring, linear glycosaminoglycan. It is composed of repeating disaccharide units of D-glucuronic acid and N-acetyl-D-glucosamine linked by alternating beta(1→3) and beta(1→4) bonds. It is non‑sulfated and highly negatively charged, enabling it to attract and retain water and form hydrated gels.

Hyaluronan is a major component of the extracellular matrix in connective tissues, skin, cartilage, and in bodily fluids such as synovial fluid, vitreous humor, and the aqueous humor of the eye. It contributes to tissue hydration, lubrication, and viscoelastic properties, and serves as a space‑filling matrix that supports cell migration during development, wound healing, and tissue repair. It interacts with cell-surface receptors such as CD44 and RHAMM, influencing signaling pathways.

Biosynthesis occurs at the inner surface of the plasma membrane by hyaluronan synthases HAS1, HAS2, and HAS3, which extrude the polymer into the extracellular space. Degradation is mediated by hyaluronidases and non-enzymatic pathways; turnover rates vary by tissue and physiological conditions, and hyaluronan fragments can have distinct biological activities, including pro‑ and anti-inflammatory effects.

Clinically, hyaluronan is used as a viscoelastic agent in ophthalmic surgery, as dermal fillers for cosmetic smoothing, and for intra‑articular viscosupplementation in osteoarthritis. It also serves as a component of wound care products and anti‑adhesion materials. Industrially, hyaluronan is produced mainly by microbial fermentation and purified for medical and cosmetic use; historically it was extracted from animal tissues such as rooster combs.

Crosslinked derivatives are used to tailor mechanical properties in medical devices and cosmetics, helping to increase resistance to enzymatic degradation and extend residence time in tissues.