824 Spatial transcriptomic analysis of HS skin lesions reveals that tunnels are immunologically active and activity correlates with disease severity

Abstract

Hidradenitis suppurativa (HS) is an inflammatory skin disease characterized by neutrophil-rich inflammatory nodules, abscesses or tunnels (sinus tracts). Tunnels, unique to HS, are deep dermal cavities lined with squamous epithelium that are immunologically active, contributing to disease pathology. The role of tunnels in driving ongoing disease is poorly understood. We used the GeoMX Digital Spatial Profiler to analyze a moderate (Hurley stage II) compared to a severe (Hurley stage III) HS skin lesion to explore biological differences between and within lesions. Four distinct regions per sample were analyzed: tunnel epithelium, immune infiltrate adjacent to a tunnel, immune infiltrate not associated with a tunnel, and sub-epidermis. We observed higher expression of keratinization genes (e.g. K16, S100A7) in the more differentiated tunnel epithelium of the severe lesion compared to the moderate lesion tunnel. Genes for proinflammatory cytokines (e.g. IL36, IL1B), chemokines (e.g. CXCL1, CCL20), neutrophil activation (e.g. ELANE, MPO) and B cells (CD79A, SDC1) had higher expression in the severe compared to moderate HS lesion. We found a spatial gradient in gene expression for IL36 and neutrophil-attracting chemokines (CXCL1, CXCL8), from high expression in the tunnel epithelium to lower expression in the sub-epidermis. Both lesions displayed these gradients, but those in the severe HS lesion were more pronounced. Conversely, spatial gradients of fibroblast-related genes (e.g. PDGFR, FAP) had higher expression in the sub-epidermis and lower expression adjacent to tunnel epithelium. These data suggest a marked increase in dermal inflammation in more severe HS lesions. The spatial gradients of cytokine and chemokine gene expression support the idea that more differentiated tunnels are more immunologically active, potentially contributing to ongoing severe disease, rather than representing remnants of prior disease.