Development of a 3D psoriatic skin model optimized for infiltration of IL-17A producing T cells: Focus on the crosstalk between T cells and psoriatic keratinocytes.

Psoriasis is a chronic inflammatory skin disease involving several cell types, including T cells, via the IL-23/IL-17 axis. IL-17A acts on the surrounding epithelial cells thus resulting in an inflammatory feedback loop. The development of immunocompetent models that correctly recapitulate the complex phenotype of psoriasis remains challenging, which also includes both the T cell isolation and activation methods. The purpose of this work was to develop an advanced in vitro 3D psoriatic skin model that enables the study of the impact of T cells on psoriatic epithelial cells. To reach that aim, healthy and psoriatic fibroblasts and keratinocytes were used to reproduce this tissue-engineered skin model in which activated T cells, isolated beforehand from human whole blood, have been incorporated. Our study showed that isolation of T cells with the EasySep procedure, followed by activation with PMA/ionomycin, mimicked the psoriatic characteristics in an optimal manner with the production of inflammatory cytokines important in the pathogenesis of psoriasis, as well as increased expression of Ki67, S100A7, elafin and involucrin. This psoriatic model enriched in activated T cells displayed enhanced production of IL-17A, IFN-Æ´, CCL2, CXCL10, IL-1ra, IL-6 and CXCL8 compared with the healthy model and whose increased secretion was maintained over time. In addition, anti-IL17A treatment restored some psoriatic features, including epidermal thickness and basal keratinocytes proliferation, as well as a downregulation of S100A7, elafin and involucrin expression. Altogether, our study demonstrated that this model reflects a proper psoriatic inflammatory environment and is effective for the investigation of epidermal and T cell interaction over time. STATEMENT OF SIGNIFICANCE: The aim of this study was to provide an innovative 3D immunocompetent human psoriatic skin model. To our knowledge, this is the first immunocompetent model that uses skin cells from psoriatic patients to study the impact of IL-17A on pathological cells. Through the use of this model, we demonstrated that the T-cell enriched psoriatic model differs from T-cell enriched healthy model, highlighting efficient crosstalk between pathologic epithelial cells and T cells. This advanced preclinical model further mimics the original psoriatic skin and will prove relevant in predicting clinical outcomes, thereby decreasing inaccurate predictions of compound effects.

Infiltration of T Cells into a Three-Dimensional Psoriatic Skin Model Mimics Pathological Key Features.

Psoriasis is an autoimmune chronic dermatosis that is T cell-mediated, characterized by epidermal thickening, aberrant epidermal differentiation and inflammatory infiltrates, with a dominant Th1 and Th17 profile. Additional in vitro models are required to study the complex interactions between activated T cells and skin cells, and to develop new, more effective treatments. We have therefore sought to model this psoriatic inflammation by the generation of tissue-engineered immunocompetent tissues, and we have investigated the response of activated T-cell infiltration in models produced with lesional psoriatic skin cells on major hallmarks of psoriasis. The immunocompetent lesional skin model displayed a delayed onset of epidermal differentiation, an hyperproliferation of the basal keratinocytes, a drastic increase in the secretion of proinflammatory cytokines, and a disturbed expression of key transcription factors, as observed in lesional plaques, suggesting a crucial importance of combining the pathological phenotype of cutaneous cells to T cells in order to generate a relevant model for psoriasis. Finally, we found this skin model to be responsive to methotrexate treatment, making it a valuable tool for drug development.

Contribution of In Vivo and Organotypic 3D Models to Understanding the Role of Macrophages and Neutrophils in the Pathogenesis of Psoriasis.

Psoriasis, a common chronic immune-mediated skin disease, is histologically characterized by a rapid keratinocyte turnover and differentiation defects. Key insights favor the idea that T cells are not the only key actors involved in the inflammatory process. Innate immune cells, more precisely neutrophils and macrophages, provide specific signals involved in the initiation and the maintenance of the pathogenesis. Current data from animal models and, to a lesser extent, three-dimensional in vitro models have confirmed the interest in leaning towards other immune cell types as a potential new cellular target for the treatment of the disease. Although these models do not mimic the complex phenotype nor all human features of psoriasis, their development is necessary and essential to better understand reciprocal interactions between skin cells and innate immune cells and to emphasize the crucial importance of the local lesional microenvironment. In this review, through the use of in vivo and 3D organotypic models, we aim to shed light on the crosstalk between epithelial and immune components and to discuss the role of secreted inflammatory molecules in the development of this chronic skin disease.