Mouse epidermal keratinocytes in three-dimensional organotypic coculture with dermal fibroblasts form a stratified sheet resembling skin

We describe an organotypic model of mouse skin consisting of a stratified sheet of epidermal keratinocytes and dermal fibroblasts within a contracted collagen gel. The model was designed to maintain the polarity of stratified keratinocytes and permit their long-term culture at an air-liquid interface. After air exposure, the thickness of the keratinocyte sheet transiently increased and then decreased to two cell layers at 2 weeks. The two-cell-layer structure is similar to that of the adult mouse epidermis. Cytokeratin 5 was localized in the lowest cell layer in the epithelial sheet, but cytokeratin 1 and loricrin were localized in the outer cell layers, resembling mouse skin. The expressions of interleukin 1 alpha and 1 beta in the keratinocytes and of keratinocyte growth factor 1 and 2 in the fibroblasts correlated with keratinocyte stratification. The mouse organotypic coculture is useful in studying epithelial cell-mesenchymal cell interactions in vitro.