RECONSTRUCTED HUMAN EPIDERMIS IN-VITRO - AN ALTERNATIVE TO ANIMAL TESTING

Various three-dimensional human skin models, in which the epidermis ex hibits in vivo-like morphological and functional characteristics, have recently been developed. Such models are currently being used to stud y the development and physiology of the skin, the processes involved i n wound healing, and the reactivity of skin to environmental and chemi cal insults. Since these models reproduce to a large extent the barrie r function properties of normal human skin, they can be used for scree ning potential skin irritants. These substances can be applied topical ly and their irritant potential can be evaluated using various endpoin ts, such as the induction of tissue damage or the release of various p ro-inflammatory mediators. Studies with human skin equivalents can the refore contribute to our knowledge of the basic biochemical mechanisms underlying irritant reactions, and can be used to understand the stru ctural features of molecules which may be responsible for eliciting an irritant reaction. In addition, the generation of epidermal equivalen ts populated with melanocytes, as well as keratinocytes, makes it poss ible to study the regulation of melanogenesis, melanocyte-keratinocyte interactions, and how these are affected by UV irradiation. Such a mo del can also be used for testing the phototoxic or photoprotective pot entials of various compounds and sunscreens.