Student Theses and Dissertations

Date of Award

2024

Document Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

RU Laboratory

Krueger Laboratory

Abstract

Hidradenitis Suppurativa is a chronic autoinflammatory disease with unknown triggers.New evidence in the last five years has begun to clarify two parts of the pathogenesis of the disease. These two parts are the fundamental role of keratinocyte inflammation from early through late-stage disease and the role of the microbiome as an antigenic and infectious trigger of pathogenesis. Gram-negative anaerobic bacteria (GNA) such as Prevotella, Porphyromonas, and Fusobacterium are commonly identified in HS lesions, and their prevalence in lesions is associated with HS disease severity. Additionally, newly epithelialized structures called “dermal tunnels” are found in severe disease and are associated with biofilm as well as the production of keratinocyte inflammatory cytokines. Our lab has previously defined the effects of gram-positive bacteria such as Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus pyogenes and found them to stimulate atopic dermatitis and psoriasis-like transcriptome profiles. In this thesis, using in vitro models of keratinocyte stimulation with heat-killed preparations of both gram-positive and gram-negative bacteria, we have explored a robust inflammatory profile generated in normal human keratinocytes by these GNAs. These GNAs elicit a strong IL17-dependent pathway response not seen in gram-positive bacteria and likely driven by IL-17C production. Overall, the magnitude of production of cytokines is much greater in all GNAs, with Fusobacterium nucleatum (FN) demonstrating the most intense activation that is mimicked to a lesser extent by Prevotella melaninogenica and Prevotella nigrescens. Significant differences in transcriptome profiles were found between all species, including members of the same species. We also find that this inflammatory response in GNAs is both TLR and JAK-dependent and that variation in cytokine production is likely driven by differential activation by TLR4 andTLR2 receptors. We then compare transcriptomes obtained from biopsies samples of HS patient lesional, perilesional, and nonlesional skin and from patients with psoriasis to GNA-keratinocyte profiles and IL17A stimulated keratinocyte profiles. We find that FN is most and significantly associated with HS gene transcriptomics. Our data is the first to provide a comprehensive profile of the effects of GNA stimulation on human keratinocytes that is more broadly applicable to innate immune epithelial defenses against GNAs. The identification of these bacteria as strong antigenic stimuli prioritizes targeting these bacteria in new therapies for HS, potentially through TLR4 or JAK inhibition.

Comments

A Thesis Presented to the Faculty of The Rockefeller University in Partial Fulfillment of the Requirements for the degree of Doctor of Philosophy

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