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The great strength and elasticity of the skin when subjected to all sorts of tension, traction and torsion, is provided by the dermis, all of these demands being cushioned mainly thanks to the extracellular matrix produced by the fibroblasts
. This matrix consists of collagen fibres, filaments interlaced as inside an electric cable, which ensure the solidity of the skin, and elastin fibres, which are finer and contribute elasticity to the whole construction.
Reconstructing epidermis on an inert support excludes its being used for studying the physical properties of the dermis, the synthesis function of fibroblasts or the effects of UVA and UVB radiation on these cells etc. It was to answer these questions that L’Oréal originally created an epidermis model on a dermal equivalent. Since then other models have been perfected using the same general technique but for other applications: the 'aged skin' model and XP skin model .
Certain models of the epidermis on a dermal equivalent, which were perfected for fundamental research, are being used to develop in vitro
methods for evaluating the efficacy of cosmetics (raw materials and finished products).
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