Hyaluronic,Acid in the Treatment and Prevention of Skin Diseases: Molecular Biological, Pharmaceutical'a-:a,d Clinical Aspects.

The glycosaminoglycan hyaluronic acid (HA), or hyaluronan. is a major component of the extracellular matrix ofskin, joints, eye and many othertissue~l and organs. In spite of its simple structure, HA demonstrates remarkable rheological, viscoelastic and hygroscopic properties which are relevant fgr dermal tissue function. Biological activities in skin, however, are also due tl) its interaction with various binding proteins' (hyaladherins). Due to an influence on signaling pathways, HA is involved in the wound-healing process and scarless fetal healing. In,
creased HA concentrations have been associated with inflammatory skin diseases. In clinical trials, topical application of HA improved wound healing; in particular, acute radioepithelitis, venous leg ulcers or diabetic foot lesions responded to HA treatment~ < Moreover, as a topical drug delivery system for diclofenac, an HA gel has recently been' approved for the treatment of actinic keratO$8s. Finally, chemical modificatio~s led to new HA derivates and biomaterials, which may be introduced into therapy in the future. Therefore, ongoing research offers new horizons for the therapeutic use of this glycosaminoglycan which has been regarded as an inert structural component until recently.