A REPRODUCIBLE, STRUCTURALLY APPROPRIATE SKIN MODEL FOR DERMAL SAFETY AND EFFICACY TESTING.

The ability to determine, in vitro, the safety and efficacy profile for a material contacting the skin critically depends on the skin model’s structure and biochemistry. In addition, to be useful, the model must have a high level of intra-lot and inter-lot reproducibility. For this reason, the structure, biochemical nature, and reproducibility of the organotypic skin model, EpiDerm, was investigated. Using light microscopy, histological cross sections showed basal, spinous, granular, and stratum corneum layers, similar to epidermis. Using immuno-histochemistry, epidermis-specific proteins including pro-filaggrin, cyto-keratins 1 and 10, keratohyalin, and glucocerebrosidase were localized in the appropriate cellular layers. Transmission electron microscopy revealed lamellar lipid bilayers spaced in the two patterns characteristic of in vivo stratum corneum. Regarding reproducibility, quality control testing on each lot of tissue consists of exposing the tissue to 1% Triton X-100 (TX) and a negative control (NC), ultrapure water. Using the MTT assay, an exposure time which reduced the tissue viability to 50% (ET-50) was determined. In 1995 (112 lots), the ET-50 for TX averaged 6.64± 0.79 hrs; the optical density (OD) for NC was 1.495±0.126; in 1999 (146 lots), the averages were 6.75±1.25 and 1.537± 0.175. Assays for dermal irritancy, corrosivity, and phototoxicity have been developed. Correlation of in vivo irritation data to in vitro assay results for 4 sets of materials gave correlation coefficients of 0.85 and 0.96. For corrosivity, sensitivity of 87.5%, and specificity of 86.1% were obtained in a multi-lab, international blinded study. In a similar multi-lab phototoxicity study, the sensitivity and specificity were 86.7% and 93.3%, respectively. Thus, the tissue model provides a non-animal means to test cosmetic products for a variety of skin related issues.

Corrosion, Corrosivity, Corrosivity testing, Cutaneous irritancy, Cutaneous irritation, Cutaneous toxicity, Cyto-keratins, Dermal corrosion, Dermal irritancy, Dermal irritancy testing, Dermal irritation, Dermal safety, ECVAM, Efficacy testing, EpiDerm, Glucocerebrosidase, Keratohyalin, MTT, MTT ET-50 tissue viability assay, MTT assay, Phototoxicity, Pro-filaggrin, Reproducibility, Reproducible, Reproducible, Skin corrosion, Skin corrosivity, Skin irritancy, Skin irritation, Skin model, Sun screens, UVA, UVB