Hyaluronic acid (HA), also known as hyaluronan, is a large, linear polysaccharide (glycosaminoglycan) that is naturally present in connective tissues, skin, joints, and eyes. Unlike other glycosaminoglycans, hyaluronic acid is not sulfated and does not bind to a core protein, meaning it is not a proteoglycan—but it can interact with proteoglycans to support structural and functional roles in tissues.
Structure:
Composed of repeating disaccharide units of:
Glucuronic acid
N-acetylglucosamine
Forms very long chains (up to millions of Daltons in molecular weight)
Highly hydrophilic, binding large amounts of water
Functions:
Hydration: Retains water, maintaining tissue moisture and volume.
Lubrication: Provides a slick surface in joints, especially in synovial fluid.
Shock absorption: Helps cushion joints and eyes.
Wound healing: Promotes cell migration and tissue repair.
Scaffold for ECM assembly: Binds to proteoglycans like aggrecan in cartilage to form large hydrated complexes.
