Hyaluronic acid is also a major component of skin, where it is involved in tissue repair. When skin is exposed to excessive UVB rays, it becomes inflamed (sunburn) and the cells in the dermis stop producing as much hyaluronan, and increase the rate of its degradation. Hyaluronan degradation products then accumulate in the skin after UV exposure.
HA plays an important role in the normal epidermis. HA also has crucial functions in the reepithelization process due to several of its properties. It serves as an integral part of the extracellular matrix of basal keratinocytes, which are major constituents of the epidermis; its free-radical scavenging function and its role in keratinocyte proliferation and migration.
In the early inflammatory phase of wound repair, wounded tissue is abundant in HA, probably a reflection of increased synthesis. HA acts as a promoter of early inflammation, which is crucial in the whole skin wound-healing process.
Although inflammation is an integral part of granulation tissue formation, for normal tissue repair to proceed, inflammation needs to be moderated. The initial granulation tissue formed is highly inflammatory with a high rate of tissue turnover mediated by matrix degrading enzymes and reactive oxygen metabolites that are products of inflammatory cells. Stabilization of granulation tissue matrix can be achieved by moderating inflammation. HA functions as an important moderator in this moderation process, which contradicts its role in inflammatory stimulation, as described above. HA can protect against free-radical damage to cells. This may attribute to its free-radical scavenging property, a physicochemical characteristic shared by large polyionic polymers. In a rat model of free-radical scavenging property, HA has been shown to reduce damage to the granulation tissue.