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CHARACTERIZATION OF THE EPIDERM™ HUMAN 3-D SKIN MODEL FOR GENOTOXICITY TESTING.
Aardema1, M., Curren2, R., Hayden3, P., Mun2, G., Gibson1, D., Hu1, T.
1The Procter & Gamble Co., Cincinnati, OH, USA; 2Institute for In Vitro Sciences, Gaithersburg, MD, USA; 3MatTek Corp., Ashland MA, USA.
Presented at 5th World Congress, Berlin, Germany, August, (2005).
Keywords: 7th Amendment to the cosmetic directive, Affymetrix gene expression analysis, Clastogenic and aneugenic chemicals, Cosmetics, Cytochalasin B (Cyt B) micronucleus assay, Cytochrome P450, Cytokinesis-block methodology, EPI-200, EU 7th Amendmendment, EpiDerm, Genotoxicity assay, Genotoxicity testing, Metabolism, REACH program, RT-PCR, Tissue specificity, Xenobiotic gene analysis, Xenobiotic metabolism
Endpoints: Affymetrix gene expression, Cytochrome P450, Gene Analysis, Genotoxicity testing, MTT assay, RT-PCR
Materials Tested: Methylmethane sulfonate (MMS), Micronucleus assay, Mitomycin C, N-methyl-N’-nitro-N-nitrosoguanidine (MNNG), Vinblastine sulphate
Summary:
To meet the requirements of the EU 7th Amendment to the Cosmetics Directive, starting in 2009, manufacturers of cosmetics products will need to assess the genotoxicity of ingredients using non-animal methods. Thus, standard assays like the in vivo micronucleus assay can no longer be a part of a testing battery to clarify the genotoxicity of chemicals positive in standard in vitro genotoxicity tests. Since standard in vitro genotoxicity assays have such a high false positive rate (Kirkland et al., 2005), the inability to use in vivo follow-up methods will create a serious problem in the safety assessment process.
One of the target tissues of interest for many cosmetic products is skin, which is generally the tissue with the highest exposure to ingredients in cosmetics. Based on this, scientists at The Procter & Gamble Co., the Institute for In Vitro Sciences (IIVS), and MatTek Corp. have developed an in vitro cytochalasin B (Cyt B) micronucleus assay in the human 3-D EpiDerm™ skin model (MatTek Corp., Ashland, MA) for potential use as an “in vivo-like” genotoxicity assay.
Studies have now been conducted with model genotoxins including mitomycin C, vinblastine sulfate, methylmethane sulfonate (MMS), and N-methyl-N’-nitro-N-nitrosoguanidine (MNNG).
Results from these studies show that micronuclei can be reproducibly induced in the EpiDerm engineered 3-D human skin model after topical exposure. Gene expression data from EpiDerm tissues from different donors are being analyzed for expression of genes involved in xenobiotic metabolism to help further characterize this model.
The micronucleus assay in the human 3D EpiDerm model appears to be a promising new tool for genotoxicity testing.
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