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

Abstract

Chronic nodular prurigo (CNPG) is an inflammatory skin disease that is maintained by a chronic itch-scratch cycle likely rooted in neuroimmunological 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. This study aimed to improve the understanding of pathomechanisms underlying CNPG as well as molecular relationships between CNPG and atopic dermatitis (AD). We profiled skin lesions from patients with CNPG in comparison with AD and healthy control individuals using single-cell RNA sequencing combined with T-cell receptor sequencing. 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, we also detected increased levels of neuromedin Bin fibroblasts of CNPG lesions compared with AD and HC, with neuromedin B receptors detectable on some nerve endings. 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 have a direct impact on itch fibers.