Abstract
While valuable for hazard identification, in vitro genotoxicity tests that are conducted in 2D monolayer cell cultures possess limitations to accurately envisage in vivo outcomes and may result in unnecessary follow-up in vivo studies. One limitation is their relevance to actual human exposure and the assessment of genotoxicity in tissues representative of “sites-of-first-contact” with genotoxic agents. The revised OECD testing guidelines had emphasized the need for considering site-of-first-contact effect and should be included when carrying out genotoxic hazard investigations. Till date, only in vivo studies can adequately address the oral/gastrointestinal route of exposure and there exists no validated in vitro assay for the gut for ingestible materials. Previously, we described the development of a new human Reconstructed Intestine Micronuclei Cytome (RICyt) assay using EpiIntestinal™ microtissues for site-of-contact genotoxic hazard identification of orally ingested materials. The human small intestine is where approximately 90% of the digestion and adsorption of food occurs and a major exposure site of ingested genotoxicants, thus a key site for evaluation. Here, we have conducted an investigation on the predictive performance of the RICyt assay. The assay platform was challenged with a training set of 16 test materials which include standard reference genotoxins and non-genotoxins as well as food relevant substances with various mode of actions. The overall RICyt accuracy was 92.9% with sensitivity of 83.3% and specificity of 100%. Majority of the test materials were correctly identified during this within-laboratory investigation though yielded one false negative and two equivocal outcomes. These results emphasize that the RICyt assay in EpiIntestinal™ microtissues has adequate predictivity and is a promising in vitro tool for genotoxic hazard identification of orally ingested substances.