Hyaluronic acid (HA) is a key glycosaminoglycan found in the extracellular matrix, widely recognized for its excellent biocompatibility and exceptional water-binding capacity. This naturally occurring polysaccharide plays crucial roles in tissue hydration, lubrication, and cellular regulation across diverse medical and biological fields. Research traces its progression from initial isolation in 1934 to the development of sophisticated biomedical formulations used today.

Chemical Structure

HA is composed of repeating disaccharide units of D-glucuronic acid and N-acetyl-D-glucosamine, forming non-sulfated linear chains that may reach molecular weights of several million daltons. It is synthesized by hyaluronan synthases (HAS1, HAS2, HAS3) located at the plasma membrane, where the polymer is extruded directly into the extracellular matrix without Golgi involvement. This unique biosynthetic mechanism enables exceptionally high molecular weights, typically between 3–7 MDa in human synovial fluid, contributing to the molecule’s remarkable viscoelastic properties.

Biological Functions

HA maintains tissue hydration by binding up to 1,000 times its weight in water, supporting skin elasticity, joint lubrication, and wound healing. It regulates inflammation, cell migration, and cell proliferation through interactions with receptors such as CD44, although endogenous levels gradually decline with age. During tissue injury, HA synthesis increases, triggering immune activation and promoting fibroblast recruitment and activity.

Biomedical Applications

HA-based hydrogels act as space-filling biomaterials in tissue engineering, supporting cartilage, bone, and skin regeneration due to their anti-inflammatory properties and ability to enable sustained therapeutic release. In osteoarthritis, HA viscosupplementation restores synovial fluid lubrication, while dermal fillers reduce visible signs of aging by enhancing hydration and structural support. In oncology, HA’s affinity for overexpressed receptors on certain tumor cells enables targeted drug delivery strategies.

Clinical Evidence

Meta-analyses consistently demonstrate that HA accelerates wound healing in burns, diabetic ulcers, and surgical incisions, with outcomes superior to controls in most clinical studies. Topical HA formulations improve skin hydration, elasticity, and overall quality, offering effective non-invasive anti-aging benefits. Data from both human and veterinary studies validate its biodegradability, safety, and low immunogenicity across a broad range of therapeutic applications.