Development of an in vitro psoriatic skin model by tissue engineering

Background: Psoriasis is a chronic skin disease characterized by a thickening and disorganization of the skin's protective barrier. Objectives: This study aims to develop and characterize a novel in vitro psoriatic human skin model produced by tissue engineering. Methods: The self-assembly method, a tissue engineering approach based on the capacity of mesenchymal cells, such as fibroblasts, to create their own extracellular matrix in vitro, was used to create our substitutes. Manipulatable sheets of fibroblasts were superimposed creating a new dermis upon which keratinocytes are seeded, leading to a complete bilayered skin substitute. The characterization of the psoriatic substitutes was performed by macroscopic, histological and immunohistochemical analyses and contrasted to those constructed from healthy cells. Results: Macroscopically, the psoriatic substitutes were more white and thicker than the healthy substitutes. The histological analysis of psoriatic substitutes stained with Masson's trichrome revealed a characteristic thickening of the epidermal layer seen in psoriatic skin in vivo. Immunohistochemical analysis of the psoriatic substitutes showed, among other things, an overexpression of involucrin and an underexpression of filaggrin and loricrin. Conclusion: These data suggest that the macroscopic, histological and immunohistochemical characteristics of psoriasis are partially retained in the substitutes, thus providing a good model to investigate the mechanisms of abnormal keratinocyte growth and to study cell-cell interactions. (c) 2008 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.