Single-cell RNA sequencing defines disease-specific differences between chronic nodular prurigo and atopic dermatitis

Background: Chronic nodular prurigo (CNPG) is a chronic inflammatory skin disease that is maintained by a chronic itch-scratch cycle likely rooted in neuro-immunological dysregulation. This condition may be associated with atopy in some patients, and there are now promising therapeutic results from blocking type-2 cytokines such as IL-4, IL-13 and IL-31. Nevertheless, underlying pathomechanisms as well as the molecular relationship with atopy remain ill-defined. Methods: We profiled skin lesions from patients with CNPG in comparison to atopic dermatitis (AD) and healthy control (HC) individuals using single-cell RNA sequencing combined with T-cell receptor sequencing. Results: We found type-2 immune skewing in both CNPG and AD, as evidenced by CD4+ helper T cells expressing IL13. However, only AD harbored an additional, oligoclonally expanded CD8A+ IL9R+ IL13+ cytotoxic T cell population, and immune activation pathways were highly upregulated in AD, but less so in CNPG. Conversely, CNPG showed signatures of extracellular matrix organization, collagen synthesis, and fibrosis, including a unique population of CXCL14- IL24+ secretory-papillary fibroblasts. Besides known itch mediators such as IL31 and oncostatin M (OSM), we also detected increased levels of neuromedin B (NMB) in fibroblasts of CNPG lesions compared to AD and HC, with NMB receptors detectable on some nerve endings. Conclusion: These data show that CNPG does not harbor the strong disease-specific immune activation pathways that are typically found in AD, but is rather characterized by upregulated stromal remodeling mechanisms that might directly impact itch fibers. Comparison of skin cells obtained from PN, AD and HC donors. Raw data is not provided due to patient privacy concerns. Healthy Control samples 112 – HC1, 115 – HC2, 116 – HC3 and 121 – HC4 used in this manuscript are already publicly available via Gene Expression Omnibus GSE173205.