INTRA- AND INTER-LOT VARIABILITY OF EPIDERM, AN EPIDERMAL MODEL FOR DERMAL RESEARCH AND TESTING.
A model of the human epidermis, EpiDerm, cultured from neonatal, nor-mal human epidermal keratinocytes has been sold commercially by MatTek Cor-poration since April 1993. Using serum free media, weekly batches of EpiDerm are produced and shipped for dermal irritancy, product efficacy, percutaneous absorption, and basic skin research studies. For all applications, it is important to know that the model is reproducible both within a given lot and between lots. In order to assess its reproducibility, each lot of tissue is exposed to 2 commonly used surfactants, Triton X-100 (TX) and sodium dodecyl sulfate (SDS), and a negative control, ultrapure water; in addition, routine histology is performed to evaluate structural reproducibility. Using 3 exposure times, N=2 tissues, and the MTT assay, a dose response curve is constructed and an effective time which reduces the metabolic activity by 50% (ET-50) is interpolated for each surfactant. The average ET-50’s for TX and SDS for 112 lots produced in 1995 are 6.65 ± 0.79 and 0.92 ± 0.23 hours, respectively; the negative control has a coefficient of variation (c.v.) of 8.4% for the same lots. Within individual lots, the MTT response for the negative control has an average c.v. of 4.9% (N=112) and for all positive and negative controls an average c.v. of 10.3%. Using light microscopy, histological H&E cross-sections show an epidermis-like morphology which is reproducible both within and between lots. Finally, immuno-staining shows the presence of many epidermal proteins such as cytokeratins K1 and K10, pro-filaggrin, transglutaminase, β-glucocerebrosidase, and involucrin, among others. Hence, EpiDerm appears to be a functional and structurally reproducible skin analog useful for dermal toxicology and other skin related studies.
Dermal, Dermal absorption, EpiDerm, MTT, MTT ET-50 tissue viability assay, MTT assay, Percutaneous absorption, Percutaneous penetration, Reproducibility, Reproducible, Sodium dodecyl sulfate (SDS), Surfactants, Transdermal
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