Using the hair follicle ex vivo model to explore initial events in hidradenitis suppurativa pathogenesis

Summary: Abstract Body: In Hidradenitis Suppurativa (HS), hair follicle (HF) keratinocytes hyperproliferate and release pro-inflammatory chemokines that attract immune cells. The molecular mechanisms beyond these initial events of HS remain elusive. Here, we evaluated the potential of the human HF organ culture model to explore early events in HS pathogenesis and as a screening tool to pre-clinically test HS therapeutics. Full-length anagen HFs from 2 male healthy donors were stimulated with, 1) a triple cytokine cocktail of TNF-α, IL-17A, and IL-1β - linked to HS pathogenesis and targeted in the clinic, 2) the triple cocktail + IFN-γ – to include Th1 responses, 3) the triple cocktail + TGF-β – to model fibrosis phenotype, or 4) vehicle control. Gene expression analysis showed that the triple cocktail had a minor effect on IL1A, LCN2, and CAMP but significantly upregulated DEFB4, CCL20, and CXCL8 expression, suggesting a pro-inflammatory phenotype promoting immune cell recruitment and bacterial dysbiosis. In line, increased CXCL8 secretion was confirmed by ELISA. Surprisingly, the triple cocktail also inhibited keratinocyte proliferation and differentiation, demonstrated by downregulation of KRT1, FLG, and MKI67. Further administration of IFN-γ or TGF-β caused only minimal additional effects. To evaluate immune cell activation and attraction, elicited by HF keratinocyte CXCL8 production, we pre-stimulated with the triple cocktail full-length HFs from 2 healthy female donors, and co-cultured them with donor-matched PBMCs. Qualitative analysis confirmed immune cell infiltration in the HFs and enhanced CXCL8 released was detected in the medium of pre-stimulated and co-cultured HFs, indicating PBMC-HF cross-talk. These pilot data highlight TNF-α, IL-17A, and IL-1β as key drivers of HS pathogenesis, particularly in inducing a pro-inflammatory phenotype in HF keratinocytes. Additionally, this study supports the use of the HF organ culture as a model to investigate HS-related mechanisms and for pre-clinical testing of potential HS treatments. Onur Egriboz¹, Ilaria Piccini¹, Janin Edelkamp¹, Marta Bertolini¹ 1. QIMA Life Sciences, Monasterium, Münster, Germany. Adaptive and Auto-Immunity