Development and characterization of a human Th17‐driven ex vivo skin inflammation model

Skin models mimicking features of psoriasis‐related inflammation are needed to support the development of new drugs in dermatology. Reconstructed skin models lack tissue complexity, including a fully competent skin barrier, and presence and/or diversity of immune cells. Here, we describe InflammaSkin®, a novel human Th17‐driven ex vivo skin inflammation model. In this model, skin‐resident T cells are in situ activated by intradermal injection of anti‐CD3 and anti‐CD28 antibodies and Th17 cell polarization is sustained by culture in a chemically defined medium supplemented with IL‐1β, IL‐23 and TGF‐β for seven days. The acquired Th17 signature is demonstrated by the sustained secretion of IL‐17A, IL‐17AF, IL‐17F, IL‐22, IFN‐γ, and to some degree IL‐15 and TNF‐α observed in the activated ex vivo skin inflammation model compared with the non‐activated skin model control. Furthermore, expression of S100A7 and Keratin‐16 by keratinocytes and loss of epidermal structure integrity occur subsequently to in situ Th17cell activation, demonstrating cellular crosstalk between Th17 cells and keratinocytes. Finally, we demonstrate the use of this model to investigate the modulation of the IL‐23/IL‐17 immune axis by topically applied anti‐inflammatory compounds. Taken together, we show that by in situ activation of skin‐resident Th17 cells, the InflammaSkin® model reproduces aspects of inflammatory responses observed in psoriatic lesions and could be used as a translational tool to assess efficacy of test compounds.