Pre-validation of an in vitro skin irritation test for medical devices using the reconstructed human tissue model EpiDerm™.

Assessment of dermal irritation is an essential component of the safety evaluation of medical devices. Reconstructed human epidermis (RhE) models have replaced rabbit skin irritation testing for neat chemicals and their mixtures (OECD Test Guideline 439). However, this guideline cannot be directly applied to the area of medical devices (MD) since their non-toxicity assessment is largely based on the testing of MD extracts that may have very low irritation potential. Therefore, the RhE-methods previously validated with neat chemicals needed to be modified to reflect the needs for detection of low levels of potential irritants. A protocol employing RhE EpiDerm was optimized in 2013 using known irritants and spiked polymers (Casas et al., 2013, TIV). In 2014 and 2015 MatTek In Vitro Life Science Laboratories (IVLSL) and RIVM assessed the transferability of the assay. After the successful transfer and standardization of the protocol, 17 laboratories were trained in the use of the protocol in the preparation for the validation. Laboratories produced data with 98% agreement of predictions for the selected references and controls. We conclude that a modified RhE skin irritation test has the potential to address the skin irritation potential of the medical devices. Standardization and focus on the technical issues is essential for accurate prediction.

Organotypic human oral tissue models for toxicological studies.

Three-dimensional models of the human oral epithelia have been developed to test the irritation of oral-care products and to provide systems to study the pathology of the oral cavity. The in vitro tissue models, cultured using normal oral epithelial cells and serum free medium, adopt a buccal or gingival phenotype. The buccal tissue (designated ORL-200) is 8-12 cell layers thick and non-cornified; the gingival tissue (designated GIN-100) is 9-13 layers thick and cornified at the apical surface. The tissues express cytokeratins 13 and 14 similar to their corresponding native oral tissues. The MTT viability assay was used to assess inter-lot and intra-lot reproducibility. The MTT average intra-lot coefficient of variation (CV) was less than 10% for both tissues and the time required to reduce tissue viability by 50% (ET-50) following application of 1% Triton-X 100 averaged 1.02+/-0.33 h (n=26) and 7.97+/-0.80 h (n=14) for the buccal and gingival tissues, respectively. The utility of the buccal tissue for irritation studies was examined by testing prototype dentifrice formulations and commercially available products including mouthwashes, toothpastes, and oral cleansers. Use of the MTT ET-50 assay and cytokine release clearly differentiated between the formulations and the oral care products. In conclusion, the oral tissue models represent highly reproducible, non-animal means to screen the irritation potential of newly developed oral care products and should be useful to study the innate immunity, biology, and pathology of the oral mucosa.