Differential Features between Chronic Skin Inflammatory Diseases Revealed in Skin-Humanized Psoriasis and Atopic Dermatitis Mouse Models.

Psoriasis and atopic dermatitis are chronic and relapsing inflammatory diseases of the skin affecting a large number of patients worldwide. Psoriasis is characterized by a T helper type 1 and/or T helper type 17 immunological response, whereas acute atopic dermatitis lesions exhibit T helper type 2-dominant inflammation. Current single gene and signaling pathways-based models of inflammatory skin diseases are incomplete. Previous work allowed us to model psoriasis in skin-humanized mice through proper combinations of inflammatory cell components and disruption of barrier function. Herein, we describe and characterize an animal model for atopic dermatitis using similar bioengineered-based approaches, by intradermal injection of human T helper type 2 lymphocytes in regenerated human skin after partial removal of stratum corneum. In this work, we have extensively compared this model with the previous and an improved version of the psoriasis model, in which T helper type 1 and/or T helper type 17 lymphocytes replace exogenous cytokines. Comparative expression analyses revealed marked differences in specific epidermal proliferation and differentiation markers and immune-related molecules, including antimicrobial peptides. Likewise, the composition of the dermal inflammatory infiltrate presented important differences. The availability of accurate and reliable animal models for these diseases will contribute to the understanding of the pathogenesis and provide valuable tools for drug development and testing.

In vivo assessment of acute UVB responses in normal and Xeroderma Pigmentosum (XP-C) skin-humanized mouse models.

In vivo studies of UVB effects on human skin are precluded by ethical and technical arguments on volunteers and inconceivable in cancer-prone patients such as those affected with Xeroderma Pigmentosum (XP). Establishing reliable models to address mechanistic and therapeutic matters thus remains a challenge. Here we have used the skin-humanized mouse system that circumvents most current model constraints. We assessed the UVB radiation effects including the sequential changes after acute exposure with respect to timing, dosage, and the relationship between dose and degree-sort of epidermal alteration. On Caucasian-derived regenerated skins, UVB irradiation (800 J/m(2)) induced DNA damage (cyclobutane pyrimidine dimers) and p53 expression in exposed keratinocytes. Epidermal disorganization was observed at higher doses. In contrast, in African descent-derived regenerated skins, physiological hyperpigmentation prevented tissue alterations and DNA photolesions. The acute UVB effects seen in Caucasian-derived engrafted skins were also blocked by a physical sunscreen, demonstrating the suitability of the system for photoprotection studies. We also report the establishment of a photosensitive model through the transplantation of XP-C patient cells as part of a bioengineered skin. The inability of XP-C engrafted skin to remove DNA damaged cells was confirmed in vivo. Both the normal and XP-C versions of the skin-humanized mice proved proficient models to assess UVB-mediated DNA repair responses and provide a strong platform to test novel therapeutic strategies.