309 The psoriasis–associated IL-17A interferes with keratinocyte differentiation and skin barrier formation in 3D skin models

Abstract

Psoriasis is one of the most prevalent inflammatory skin diseases and IL-17A has been identified as a key cytokine in the pathogenesis of the disease. Therefore we investigated the effects of IL-17A on the formation and the functionality of the skin barrier in human organotypic 3D skin equivalents. On the one hand we applied a novel full thickness psoriasis model implying human epidermal keratinocytes (NHEKs) and dermal fibroblasts (HDFs) from psoriatic lesions of patients and on the other hand we used control models containing cells from healthy donors. Stimulation with IL-17A revealed changes in skin morphology in both models including parakeratosis and varying epidermal thickness. Microarrays and immunohistological stainings revealed down-regulation of genes and proteins important for epidermal differentiation, including filaggrin and loricrin. In addition, we detected increased expression of several antimicrobial peptides (AMPs), including human beta defensins (hBDs) and members of the S100 calcium binding family. While the same gene clusters were deregulated upon IL-17A treatment in both models, we observed qualitative differences with some genes being deregulated more substantially in the psoriatic model. Among the IL-17A induced genes were the IL-36 cytokines. We hypothesized that these are downstream effectors of IL-17A. Indeed all isoforms of IL-36 showed alterations in NHEK differentiation and skin barrier formation and they induced the expression of AMPs as well as IL-36 cytokines themselves. In addition the effects of IL-17A were abrogated with Secukinumab, an IL-17A antibody, which was recently approved for the treatment of psoriasis. In conclusion we established full thickness 3D psoriatic skin models containing NHEKs and HDFs of psoriasis patients. In these and in control models IL-17A interfered with keratinocyte differentiation. Our results suggest that IL-36 cytokines mediate in part the IL-17A effects.

Long-Term and Clinically Relevant Full-Thickness Human Skin Equivalent for Psoriasis

“…In the collagen models, fibroblasts are embedded in collagen I gels, which function as dermal equivalents . Collagen models can demonstrate characteristic psoriatic phenotypes like epidermal hyperplasia and hypogranulosis and express typical disease markers like HBD-2, SKALP/elafin, and/or S100A7, , but these models suffer from poor mechanical strength, contraction, and a limited life span . Typically, these full-thickness skin models start to degrade after approximately 14 days.…”