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Psoriasis is a skin disease characterized by the presence of red plaques on the skin. This pathology is well-known to be a retinoid-sensitive disease. Previous investigations have shown that retinoids can modulate epidermal proliferation with an antiproliferative potential in hyperproliferative skins. The aim of this study was to compare the development of psoriatic substitutes cultured in a retinoic acid supplemented medium with those cultured in medium receiving no supplement, to define the effects of this growth factor on keratinocyte proliferation and differentiation. The self-assembly method was used to create substitutes. Characterization of the psoriatic substitutes was performed by histological and immunolabeling analyses. Results showed that psoriatic keratinocyte substitutes cultured with retinoic acid have a thinner epidermis compared with psoriatic keratinocyte substitutes cultured without this supplement. Further, the expression of all tested cell differentiation markers was restored in psoriatic keratinocyte substitutes cultured in presence of retinoic acid. No significant change in epidermal thickness or in the expression of late differentiation markers was observed in healthy keratinocyte substitutes cultured with or without retinoic acid; however, some changes were reported for proliferation and early differentiation markers. Results suggest that retinoic acid can modulate epidermal differentiation and proliferation with an antiproliferative potential in psoriatic substitutes such as observed in psoriatic skin in vivo.

Previous studies have reported that well-defined culture conditions can improve keratinocytes terminal differentiation and reproducibility. The aim of our study was to compare skin substitutes cultured in a complete medium with those cultured in a serum-free medium at the air-liquid interface to optimize the self-assembly method. Skin substitutes, cultured in a serum-free medium over 7, 14, and 21 days, were compared with others cultured in a complete medium (5% serum) over the complete culture period. Masson's Trichrome staining showed that the substitutes cultured in a serum-free medium generated a well-developed and differentiated epidermis. Immunolabeling analyses between the substitutes cultured without serum and those cultured in complete serum showed similar expression of epidermal differentiation markers, dermo-epidermal junction, and dermal extracellular matrix components. On the basis of our Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) results, the skin substitutes cultured in serum-free condition over 21 days of culture at the air-liquid interface showed lower frequencies of the CH(2) symmetric mode of vibrations, which means a better lipid organization of the stratum corneum. No significant difference in hydrocortisone penetration was observed between serum-free medium substitutes and the controls. Results demonstrate that the absence of serum does not compromise the characteristics of the skin substitutes observed in this study.

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