Single-cell transcriptomics suggest distinct upstream drivers of IL-17A/F in hidradenitis versus psoriasis

Background: Based on the mounting evidence that Type 17 T-cells (T17 cells) and increased IL-17 play a key role in driving hidradenitis suppurativa (HS) lesion development, biologics previously used in psoriasis that block signaling of IL-17A and/or IL-17F isoforms have been repurposed to treat HS. Objective: Our aim was to characterize the transcriptome of HS T17 cells compared to the transcriptome of psoriasis T17 cells, and their ligand-receptor interactions with neighborhood immune cell subsets. Methods: Single-cell data of 12,300 cutaneous immune cells from 8 de-roofing surgical HS skin samples that included dermal tunnels were compared with single-cell data of psoriasis skin (19,525 cells from 11 samples) and control skin (11,920 cells from 10 samples). All the single-cell data were generated by the identical protocol. Results: HS T17 cells expressed lower levels of IL23R and higher levels of IL1R1 and IL17F compared to psoriasis T17 cells (p < 0.05). HS regulatory T-cells (Tregs) expressed higher levels of IL1R1 and IL17F compared to psoriasis Tregs (p < 0.05). Semimature dendritic cells (DCs) were the major immune cell subsets expressing IL1B in HS, and IL-1B ligand-receptor interactions between semimature DCs and T17 cells were increased in HS compared to psoriasis (p < 0.05). HS dermal tunnel keratinocytes (KCs) expressed inflammatory cytokines (IL17C, IL1A, IL1B, and IL6) different from HS epidermis KCs (IL36G) (p < 0.05). IL6, which synergizes with IL1B to maintain cytokine expression in T17 cells, was mainly expressed by fibroblasts in HS, which also expressed IL11+ inflammatory fibroblast genes (IL11, IL24, IL6, and POSTN) involved in paracrine IL-1/IL-6 loop. Conclusion: The IL-1B-T17 cell cytokine axis is likely a dominant pathway in HS with HS T17 cells activated by IL-1B signaling, unlike psoriasis T17 cells which are activated by IL-23 signaling. Clinical Implication: Biologics targeting IL-17 isoforms and IL-1B may be effective for HS but biologics targeting IL-23 may be less effective for HS. Emigrating cells from 28 samples of lesional & nonlesional human psoriasis skin and normal control skin were obtained via 6 mm punch skin biopsy and subjected to single-cell RNA sequencing analysis. Data include 11 psoriasis lesional skin samples before secukinumab treatment, 4 psoriasis lesional skin samples 12 weeks after secukinumab treatment, 1 psoriasis lesional skin sample 24 weeks after secukinumab treatment, 1 psoriasis lesional skin sample 48 weeks after secukinumab treatment, 1 psoriasis nonlesional skin sample before secukinumab treatment and 10 control skin samples from healthy volunteers. Data include 14 samples from GSE151177, which are generated under the identical experiment protocol by the identical investigators.