INITIAL CHARACTERIZATION OF A NEW MODEL FOR DERMAL IRRITANCY TESTING.

A model of the human epidermis, EpiDerm™, based on neonatal foreskin-derived normal human epidermal keratinocytes (NHEK) has recently been introduced by MatTek Corporation. Cultured using serum free media in easily handled Millicell® CM (Millipore Corp.) cell culture inserts, the model allows application of liquid and solid test materials (potential dermal irritants) directly to the apical surface (“stratum corneum”) of this air-lifted, highly differentiated culture. Initial characterization of this new in vitro model includes: 1) histology using H&E staining and light microscopy, 2) ultrastructure using TEM, 3) identification and localization of epidermis specific proteins using immunohistochemistry, 4) mitotic activity using tritiated thymidine uptake, 5) metabolic activity as evidenced by MTT and neutral red reactions, and 6) release of epidermal cytokines known to be important in dermal irritation. This work provides the theoretical underpinnings for use of EpiDerm as a model to study dermal irritation in vitro.