Occupational safety assessment of skin corrosion/irritation using human reconstituted epidermis models.

The assessment of skin corrosion/irritation is an essential part of the safety evaluation of chemicals and is therefore demanded by international regulatory requirements. Because of ethical considerations and sometimes limited availability of compound for in-vivo tests, alternative methods, including human reconstituted epidermis (hREP) models, gain more and more importance.In an in-house validation study with hREP models we used known corrosive or irritating chemicals and determined cell viability (MTT-assay) as the basis for classification of the respective hazard. The results of viability testing provided a good prediction for a wide spectrum of chemicals (e.g. organic acids and bases, anorganics, phenols). In addition, hematoxylin and eosin stained sections of the epidermis at the end of the study and the release of IL-1alpha in the assay medium were evaluated in order to investigate different endpoints for classification. In a comparability study for skin irritation performed together with ZEBET a good intra- and interlaboratory reproducibility of MTT-results could be shown over time and with separate lots of tissues. Therefore, in-vitro skin corrosion and irritation assays using hREP models have now been implemented in the sequential testing strategy according to OECD test guideline 404 in our laboratory along with the evaluation of structure-activity-relationship (SAR) data and measurement of pH-value.In conclusion, we have successfully established hREP models for the prediction of skin corrosion and irritation using cell viability as primary endpoint. These tests are integrated in a sequential test strategy for occupational safety assessment and replace the use of laboratory animals.