Hyaluronan or hyaluronic acid (HA) is a non-sulfated glycosaminoglycan.
Hyaluronic acid is found in skin, cartilage, and the vitreous humour of the eye.
HA plays an important role in connective and epithelial tissue repair.
HA is unique among the glycosaminoglycans in that it lacks sulfate.
Hyaluronic acid is a major component of skin, specifically, the connective tissue matrix of he dermis.
The dermis is the dense layer of skin that lies below the epidemis.
Hyaluronic acid is intricately involved in the repair of skin and its absence contributes to aging.
For example, when skin is exposed to excessive sun rays, it becomes inflamed or sun-burned.
When this occurs, the cells in the dermis stop producing hyaluronan and instead increase the rate of its degradation.
Hyaluronan degradation products then accumulate in the skin.
Hyaluronan is degraded by enzymes called hyaluronidases.
The degradation products are very low-molecular-weight hyaluronan, which is thought to induce the skin's inflammatory response.