IN VITRO MODELS OF FULL-THICKNESS HUMAN SKIN (EPIDERMFT™) AND AIRWAY EPITHELIUM (EPIAIRWAYFT™) FOR TOXICOLOGY AND DRUG DEVELOPMENT APPLICATIONS.

In vitro models of human skin and airway epithelia have potential applications in toxicology studies involving chemical warfare agents, environmental chemicals or consumer products, as well as in development of therapeutics delivered via dermal or inhalation routes. However the response of epithelial cells to exogenous chemical exposure is believed to be strongly influenced by paracrine signaling from fibroblasts residing in the subepithelial stromal tissue. Thus, “full-thickness” models containing an epithelial cell layer as well as an underlying fibroblast-containing stromal matrix are desirable to more fully reproduce the in vivo situation. To enable in vitro study of phenomena in which fibroblast-epithelial cell interactions are important, highly differentiated full thickness models composed of fibroblast-containing collagen matrix and keratinocyte or airway epithelial cells were therefore developed. Histologic examination of the resultant skin equivalent shows a collagen dermis populated by numerous viable fibroblasts and an epidermis consisting of stratified keratinocytes including basal, spinous, granular and stratum corneum components. The airway equivalent also possesses a collagen matrix populated by numerous viable fibroblasts, but with pseudostratified mucociliary morphology typical of the in vivo tracheal/bronchial epithelium. An important aspect for reproducing in vivo-like function of full-thickness epithelial tissues is development of an appropriate basement membrane at the junction between the epithelium and the underlying fibroblast-containing matrix. Therefore the ultrastructure of the basement membrane was examined by transmission electron microscopy. A well-developed basement membrane was evident in both models. Hemidesmosomes were observed at the basal membranes of the epithelial cells, with associated tonofilaments extending into the cytoplasm. Well-defined, continuous lamina lucida and lamina densa and fine anchoring filaments were present beneath the basal epithelial cells. Anchoring fibrils with characteristic striated structure connected the lamina densa to the underlying collagen matrix. EpiDermFT and EpiAirwayFT overcome shortcomings of previous models in terms of providing epithelial cell/fibroblast interactions as well as appropriate in vivo-like morphology and basement membrane development. These attributes will enable more realistic in vitro toxicological studies of epithelial phenomena.

AEC, Airway epithelial cells, Airway epithelium, Anchoring fibrils, Basement membrane, Chemical warfare agents, Collagen dermis, Collagen matrix, Congress on In Vitro Biology, Consumer products, Cytoplasm, Dermal, Drug development, Environmental chemicals, EpiAirway-FT, EpiAirwayFT, EpiDerm-FT, EpiDermFT, Epithelial cells, Exogenous chemical exposure, FB, FB-epithelial cell interactions, Fibroblasts, Fine anchoring filaments, Full-thickness human skin, Granular, Hemidesmosomes, In vivo, Inhalation routes, KC, Keratinocyte, Lamina densa, Lamina lucida, Paracrine signaling, Pseudostratified mucociliary morphology, Spinous, Stratum corneum, Stromal matrix, Subepithelial stromal tissue, Therapeutics, Tonofilaments, Toxicological studies, Toxicology, Tracheal/bronchial epithelium, Transmission electron microscopy