Quantitative in vitro assessment of phototoxicity using a human skin model, Skin2.

: The ability to accurately predict the phototoxic potential of personal and skin care products remains a key element in assessing the safety of premarketed products. To find a reliable in vitro alternative test for photoirritancy, the European Commission and the European Cosmetic Association are conducting a 3-year, European validation study. Based on the results of this study, an in vitro photoirritancy method will be selected for incorporation into new international guidelines for photoirritancy testing. As a part of this study, Skin2, a cultured human skin system, was used to evaluate the phototoxic potential of chemicals with known photoirritative properties. The Skin2 ZK1351, a 3-dimensional co-culture system, consists of dermal fibroblasts and a multilayered epidermis comprising differentiated keratinocytes. This product line has previously been used to evaluate the irritative potential of topically applied ingredients and products. In this study, various concentrations of the test chemicals were applied to the epidermal side of the Skin2 tissue for contact times of 1 h or 24 h and then the tissue was exposed to 2.9 J/cm2 of ultraviolet A (UVA) radiation. Treated but nonirradiated tissues were also assayed to predict the cytotoxic potential of the test chemicals, which could mask the phototoxic reaction. After exposure, the tissue substrates were rinsed free of test chemicals and allowed to recover for 24 h. Following this incubation, the MTT reduction assay was used to assess cytotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)