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

Abstract

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.

Imiquimod‐induced ex vivo model of psoriatic human skin via interleukin‐17A signalling of T cells and Langerhans cells

“…In addition, some evidence of cell apoptosis (pyknotic nuclei and cellular vacuolization) was observed in epidermal keratinocytes after 7 days of culturing. As our model is cultured until 7 days, some histological alterations are expected, as described by others, 12 which did not compromise skin viability. Moreover, we would not expect an increase in the inflammatory cell number or blood vessel formation due to the experimental conditions of our model.…”

“…Several in vitro models using healthy or psoriatic human skin have been developed to obtain findings more similar to the psoriatic inflammation observed in patients 11 . In these models, keratinocyte cultures or reconstructed human skins are treated with Th1, Th2 and Th17 cytokine cocktails (such as IL‐17A, IL‐23, interleukin‐1β and tumor necrosis factor‐α) to mimic psoriasis‐like inflammation 12–14 . However, the models do not provide the complex interactions between different cell types observed in psoriatic skin lesions.…”

Recent progress at the psoriasis and atopic dermatitis research front: An experimental dermatology perspective

“…These innate immune responses from keratinocytes promote neutrophil recruitment, angiogenesis and activation of dendritic cells. This, in turn, produces IL23, which directs the differentiation of naïve T cells to IL17 and IL22 producing Th17 cells 13,16‐18 . IL17 is one of the key effector molecules that promote a hyperproliferative response in keratinocytes, leading to uncontrolled epidermal expansion and psoriatic plaque formation 4,13,19,20 .…”

“…Jardet et al 17 . have established an ex vivo human skin inflammation model in which fresh healthy human skin biopsies are injected intradermally with T‐cell activating antibodies and cultured ex vivo in medium supplemented with Th17 cell polarization cytokines.…”

“…In this model, keratinocytes are activated and epidermal structure integrity is lost in response to Th17 cell activation, thus reproducing key aspects of inflammatory responses observed in psoriatic skin. The authors have demonstrated that this model can be used to investigate the modulatory effect of topically applied anti‐inflammatory compounds on the IL‐23/IL‐17 immune axis 17 . Thus, this new ex vivo model can be used to study the cellular crosstalk between Th17 T cells and keratinocytes, and may be used as a translational tool to determine efficacy of drugs of interest directly in the human target organ, rather than in so‐called mouse models of PSO.…”