Induction of a Th17 Phenotype in Human Skin—A Mimic of Dermal Inflammatory Diseases

Th17 cells are a subset of effector T helper cells that produce interleukin (IL)-17A, IL-17F, IL-22, and IL-26, which can promote tissue inflammation and contribute to the pathogenesis of rheumatic, fibrosing, and other diseases. Research into these diseases is often limited by a lack of an animal model that closely mimics human disease and the paucity of patient clinical tissues. Therefore, the development of relevant experimental models is crucial. Three media formulations of Th17-skewing cocktail (CT) were evaluated for the ability to induce a Th17 signature in an ex vivo human skin model: CT9 contained αCD3, αCD28, IL-23, IL-1β, IFNγ, IL-4, IL-6, IL-21, and TGFβ; CT8 lacked IL-1β; and CT4 only contained αCD3, αCD28, IL-23, and IL-1β. Healthy donor skin was defatted, distributed as 3 mm punch biopsies, and incubated with one of the cocktail formulations or vehicle for 48 h. All of the cocktail formulations independently significantly stimulated the expression of each gene examined. CT4 induced IL-17A expression 1024-fold, significantly higher than CT9 and CT8. IL-17F was robustly stimulated by CT4 (1557-fold), CT9 (622-fold), and CT8 (111-fold), with significant differences between the CT groups. All of the formulations significantly induced IL-22 (16–42-fold). CT9 stimulated the highest IL-26 response (41-fold), which was significantly higher than CT4 and CT8. IL-10 was stimulated significantly higher with CT8 (10-fold) than CT4 or CT9. The secretion of IL-17A was significantly elevated with all cocktail formulations. Robust IL-17A/IL-17F cytokine induction was preferentially mediated by CT4, which suggested that its components are the minimal constituents necessary for the full induction of these genes in this human skin explant model, while the downstream cytokines were preferentially upregulated by CT4 (IL-22), CT9 (IL-26), or CT8 (IL-10). In summary, our findings suggest that the induction of a Th17 phenotype in human skin is feasible and can be used as a model for rheumatic and fibrosing diseases where Th17 skewing is observed.