Research for establishment of evaluation method for the skin irritation using a Three-Dimensional Cultured Human Skin Model instead of in vivo results.

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In the present report, time course of skin irritation determined by MTT assay and the relationship between skin irritation and the irritant concentration in the three-dimensional cultured human skin model as well as hairless mouse skin were analyzed using cetylpyridinium chloride (CPC) as a model test compound.1)Reaction site of the skin irritationAlthough different numbers of dead cell were found between the dorsal and abdominal skins after in vivo application of the same dose of CPC, a similar value was obtained against the skin concentration of CPC, suggesting that skin irritation is directly related to the CPC concentration where skin irritation takes place. When evaluating the in vitro data by Sigmoid Emax model, form factor, Y and the maximal value, Emax, were very similar to those in the in vivo study. Thus, the cultured cells can be used as a tool for prediction of skin irritation.2)Evaluation of CPC irritation for keratinocytes and fibroblastsSkin irritation study showed number of dead human keratiocytes was 10 times higher than that of dead human fibroblasts. This result suggests that keratinocytes, constituting the outmost layer of the skin, play an important role to protect body from the outside irritation compared to fibroblasts which were existed in deep site of the skin.