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Abstract: Recently, a novel in vitro reconstructed skin micronucleus (RSMN) assay incorporating the EpiDerm™ 3D human skin model (Curren et al., Mutat. Res. 607 (2006) 192–204; Mun et al., Mutat. Res. 673 (2009) 92–99) has been shown to produce comparable data when utilized in three different laboratories in the United States (Hu et al., Mutat. Res. 673 (2009) 100–108). As part of a project sponsored by the European cosmetics companies trade association (COLIPA), with a contribution from the European Center for the Validation of Alternative Methods (ECVAM), international prevalidation studies of the RSMN assay have been initiated. The assay was transferred and optimized in two laboratories in Europe, where dose-dependent, reproducibly positive results for mitomycin C and vinblastine sulfate were obtained. Further intra- and inter-laboratory reproducibility of the RSMN assay was established by testing three coded chemicals, N-ethyl-N-nitrosourea, cyclohexanone, and mitomycin C. All chemicals were correctly identified by all laboratories as either positive or negative. These results support the international inter-laboratory and inter-experimental reproducibility of the assay and reinforce the conclusion that the RSMN assay in the EpiDerm™ 3D human skin model is a valuable in vitro method for assessment of genotoxicity of dermally applied chemicals. [Copyright &y& Elsevier]

Abstract: The European Cosmetic Toiletry and Perfumery Association (COLIPA), along with contributions from the European Centre for the Validation of Alternative Methods (ECVAM), initiated a multi-lab international prevalidation project on the reconstructed skin micronucleus (RSMN) assay in EpiDerm™ for the assessment of the genotoxicity of dermally applied chemicals. The first step of this project was to standardize the protocol and transfer it to laboratories that had not performed the assay before. Here we describe in detail the protocol for the RSMN assay in EpiDerm™ and the harmonized guidelines for scoring, with an atlas of cell images. We also describe factors that can influence the performance of the assay. Use of these methods will help new laboratories to conduct the assay, thereby further increasing the database for this promising new in vitro genotoxicity test. [Copyright &y& Elsevier]