Characterization and comparison of reconstructed skin models: Morphological and immunohistochemical evaluation

Reconstructed human skin equivalents are currently being investigated as in vitro models for the prediction of human skin toxicity and irritation resp onses. Three different industrial reconstructed skin models (EpiDerm, Episk in and SkinEthic) and one in-house equivalent were characterized and compar ed using light microscopy, immunohistochemistry and reduction of (3-[4,5-di methylthiazole-2-yl]-2,5-diphenyl tetrazolium bromide) (MTT), Their inter- and intra-batch variation was evaluated, Histological examination showed a completely stratified epithelium in all skin models, which closely resemble d normal human epidermis, Low intra-batch variation in tissue architecture was observed in all skin models, but moderate to considerable inter-batch v ariation was noticed. Evaluation of the expression and localization of a nu mber of differentiation-specific protein markers revealed that all skin mod els showed an aberrant expression of keratin 6, skin-derived antileukoprote inase, small proline rich proteins, involucrin and transglutaminase, Althou gh variation within batches was low, in particular keratin 6, involucrin an d skin-derived antileukoproteinase expression demonstrated some inter-batch variation. Reduction of MTT in vehicle-treated cultures showed high simila rities between skin models, but marked differences were observed when 1.0% sodium lauryl sulfate was applied topically for 3 or 16 h, Most pronounced effects were noticed in SkinEthic cultures. Intra-batch variations mere low and moderate variations were observed between batches. All skin models tes ted reproduced many of the characteristics of normal human epidermis and th erefore provide a morphologically relevant ill vitro means to assess skin i rritation and other skin-related studies.