CD25 expression marks an activated mast cell population in human nasal polyposis

Background- Chronic rhinosinusitis (CRS) with nasal polyps (CRSwNP) is a Th2 disease characterized by heterogeneous mast cell hyperplasia. We previously used transcriptomics to identify discrete gene expression linked with intraepithelial MCs expressing tryptase alone (MCT), subepithelial MCs co-expressing tryptase and chymase (MCTCs), and immature MCs in CRSwNP. While MCTCs were the only subset consistently observed in both CRSwNP and control CRS donors without nasal polyposis (CRSsNP), the degree to which they differ across disease states remains unexplored. Objective- The objective of this study was to use transcriptomics and flow cytometry to compare MCTCs in CRSwNP to CRSsNP. Methods- MCTCs were flow-sorted from CRSwNP and CRSsNP samples for RNA-sequencing (RNAseq) analysis to identify differentially expressed genes and pathways across disease states. In silico observations were validated using flow cytometry on cryopreserved tissue samples from CRSwNP and CRSsNP, and RNAseq of stimulated ex-vivo differentiated MCs. Results- We find a significant increase in MCTC concentration in CRSwNP donors, which were enriched for activation associated pathways linked with differential expression of transcripts encoding pro-inflammatory mediators and cell receptors, including IL2RA. Validation studies highlighted significant cell-surface expression of CD25 on MCTCs in CRSwNP. Ex-vivo stimulated primary MCs upregulated IL2RA in response to IL-33 stimulus. Conclusions- Our data shows that MCTCs in CRSwNP exhibit an activated transcriptional phenotype with expression of transcripts encoding pro-inflammatory mediators and IL2RA. Moreover, the CD25 upregulation on MCTCs in CRSwNP suggest its potential to serve as an in-vivo marker of activated MCTCs during allergic disease.