# Transcriptomic profiling reveals distinct molecular signatures among lesion types in hidradenitis suppurativa

## TL;DR

This study identifies unique molecular patterns in different types of hidradenitis suppurativa skin lesions, highlighting the need to consider lesion type in future research and treatment.

## Contribution

The study reveals distinct transcriptomic profiles for different hidradenitis suppurativa lesion types, offering new insights into their molecular mechanisms.

## Key findings

- Inflammatory nodules show increased antigen presentation and CD8+ T cell activity.
- Draining tunnels exhibit heightened IL-1 and IL-17 signaling with upregulated MMPs and downregulated AQPs.
- Non-draining tunnels share some inflammatory features but differ in specific gene expression patterns.

## Abstract

Hidradenitis suppurativa is a painful inflammatory disease characterised by diverse cutaneous lesions that exhibit distinct clinical morphologies. The study aimed to examine the transcriptome of the various hidradenitis suppurativa lesion types.

Transcriptomic analyses were performed using bulk RNA sequencing to examine the various lesion types, including draining tunnels, inflammatory nodules, non-draining tunnels, non-lesional skin from patients with hidradenitis suppurativa and normal skin from healthy individuals.

Principal component and differential expression analyses revealed that these different lesion types exhibit distinct expression profiles while sharing common transcriptional features. Enrichment analysis of exclusively differentially expressed genes for each lesion type showed increased antigen presentation and cytotoxic T cell response in inflammatory nodules, including genes such as CD8B, HLA-C, and HLA-F. In accordance, cell-type enrichment analysis showed an elevated CD8+ T cell signature in inflammatory nodules. Gene set variation analysis demonstrated distinct inflammatory pathway signatures in hidradenitis suppurativa lesions, including heightened IL-1 signalling in draining tunnels with significant upregulation of IL1B and its receptor IL1R, but not IL1A. Furthermore, IL17A and IL17F were significantly increased in draining tunnels, inflammatory nodules, and non-draining tunnels, with IL17F showing the highest expression in draining tunnels. MMP3, MMP8, and MMP10 were preferentially upregulated in draining tunnels, indicating a role in tunnel activity. Moreover, AQP4 and AQP5 were significantly downregulated in both lesional and non-lesional hidradenitis suppurativa skin, suggesting a possible involvement in preclinical pathogenic events.

Distinct molecular signatures specific for each lesion type were identified, which may reflect differences in molecular mechanisms. These findings underscore the importance of distinguishing between lesion types in translational and clinical studies.