[Exploration of prognostic models for chronic rhinosinusitis with nasal polyps based on machine learning].

Objective: To analysis the molecular characteristics of chronic rhinosinusitis with nasal polyps (CRSwNP), to unravel its pathophysiological mechanisms, and to develop a prognostic model capable of effectively predicting postoperative recurrence. Methods: The data from three datasets (GSE198950, GSE179265, and GSE136825) were integrated, comprising 39 control cases, 16 cases of chronic rhinosinusitis without nasal polyps, and 89 cases of CRSwNP. Differential expression genes (DEGs) were identified based on adjusted P<0.05 and Log2FC>1. KEGG and GO enrichment analyses, as well as STRING node scoring, were conducted. Variable selection was performed using random forest and least absolute shrinkage and selection operator regression (LASSO), with key nodes identified through intersection analysis. Mann-Whitney U test was applied, and variables with P<0.05 were included in the model. A prognostic model for CRSwNP was constructed using logistic regression, externally validated using RNA-seq data, and evaluated with receiver operating characteristic (ROC) curve analysis to calculate the area under the curve (AUC). Results: This research illustrated both upregulated and downregulated DEGs in CRSwNP, activating pathways like neuroactive ligand-receptor interaction and IL-17 signaling, while inhibiting calcium signaling and gap junctions. Key nodes identified through random forest and LASSO, including G protein subunit γ4 (U=3.00 P=0.028), Cholecystokinin (U=0.50, P=0.006), Epidermal growth factor (U=1.00 P=0.008), and Neurexin-1 (U=0.00, P=0.004), showing statistical significance in external validation. The prognostic model, visualized in a line graph, exhibited high reliability (C-index=0.875,AUC=0.866). The ROC curve in external validation indicated its effectiveness in predicting postoperative recurrence (AUC=0.859). Conclusions: This study integrates multiple datasets on CRSwNP to provide a comprehensive description of its molecular features. The prognostic model, built upon key nodes identified through random forest and LASSO analyses, demonstrates high accuracy in both internal and external validations, thus providing robust support for the development of personalized treatment strategies for CRSwNP.

[Single-cell transcriptomic sequencing coupled with Mendelian randomization analysis elucidates the pivotal role of CTSC in chronic rhinosinusitis].

Objective: To investigate the molecular mechanisms of chronic rhinosinusitis (CRS), to identify key cell subgroups and genes, to construct effective diagnostic models, and to screen for potential therapeutic drugs. Methods: Key cell subgroups in CRS were identified through single-cell transcriptomic sequencing data. Essential genes associated with CRS were selected and diagnostic models were constructed by hdWGCNA (high dimensional weighted gene co-expression network analysis) and various machine learning algorithms. Causal inference analysis was performed using Mendelian randomization and colocalization analysis. Potential therapeutic drugs were identified using molecular docking technology, and the results of bioinformatics analysis were validated by immunofluorescence staining. Graphpad Prism, R, Python, and Adobe Illustrator software were used for data and image processing. Results: An increased proportion of basal and suprabasal cells was observed in CRS, especially in eosinophilic CRS with nasal polyps (ECRSwNP), with P=0.001. hdWGCNA revealed that the "yellow module" was closely related to basal and suprabasal cells in CRS. Univariate logistic regression and LASSO algorithm selected 13 key genes (CTSC, LAMB3, CYP2S1, TRPV4, ARHGAP21, PTHLH, CDH26, MRPS6, TENM4, FAM110C, NCKAP5, SAMD3, and PTCHD4). Based on these 13 genes, an effective CRS diagnostic model was developed using various machine learning algorithms (AUC=0.958). Mendelian randomization analysis indicated a causal relationship between CTSC and CRS (inverse variance weighted: OR=1.06, P=0.006), and colocalization analysis confirmed shared genetic variants between CTSC and CRS (PPH4/PPH3>2). Molecular docking results showed that acetaminophen binded well with CTSC (binding energy:-5.638 kcal/mol). Immunofluorescence staining experiments indicated an increase in CTSC+cells in CRS. Conclusion: This study integrates various bioinformatics methods to identify key cell types and genes in CRS, constructs an effective diagnostic model, underscores the critical role of the CTSC gene in CRS pathogenesis, and provides new targets for the treatment of CRS.

[Identification of oxidative stress-related biomarkers in chronic rhinosinusitis with nasal polyps using WGCNA combined with machine learning algorithms].

Objective: To identify diagnostic markers related to oxidative stress in chronic rhinosinusitis with nasal polyps (CRSwNP) by analyzing transcriptome sequencing data, and to investigate their roles in CRSwNP. Methods: Utilizing four CRSwNP sequencing datasets, differentially expressed genes (DEGs) analysis, weighted gene co-expression network analysis (WGCNA), and three machine learning methods for Hub gene selection were performed in this study. Subsequent validation was carried out using external datasets, as well as real-time quantitative polymerase chain reaction (Real-time qPCR), and immunofluorescence staining of clinical samples. Moreover, the diagnostic efficacy of the genes was assessed by receiver operating characteristic (ROC) curve, followed by functional and pathway enrichment analysis, immune-related analysis, and cell population localization. Additionally, a competing endogenous RNA (CeRNA) network was constructed to predict potential drug targets. Statistical analysis and plotting were conducted using SPSS 26.0 and Graphpad Prism9 software. Results: Through data analysis and clinical validation, CP, SERPINF1 and GSTO2 were identified among 4 138 DEGs as oxidative stress markers related to CRSwNP. Specifically, the expression of CP and SERPINF1 increased in CRSwNP, whereas that of GSTO2 decreased, with statistically significant differences (P<0.05). Additionally, an area under the curve (AUC)>0.7 indicated their effectiveness as diagnostic indicators. Importantly, functional analysis indicated that these genes were mainly related to lipid metabolism, cell adhesion migration, and immunity. Single-cell data analysis revealed that SERPINF1 was mainly distributed in epithelial cells, stromal cells, and fibroblasts, while CP was primarily located in epithelial cells, and GSTO2 was minimally present in the epithelial cells and fibroblasts of nasal polyps. Consequently, a CeRNA regulatory network was constructed for the genes CP and GSTO2. This construction allowed for the prediction of potential drugs that could target CP. Conclusion: This study successfully identifies CP, SERPINF1 and GSTO2 as diagnostic and therapeutic markers related to oxidative stress in CRSwNP.

S100a9 might act as a modulator of the Toll-like receptor 4 transduction pathway in chronic rhinosinusitis with nasal polyps.

Chronic rhinosinusitis with nasal polyp (CRSwNP) is a highly prevalent disorder characterized by persistent nasal and sinus mucosa inflammation. Despite significant morbidity and decreased quality of life, there are limited effective treatment options for such a disease. Therefore, identifying causal genes and dysregulated pathways paves the way for novel therapeutic interventions. In the current study, a three-way interaction approach was used to detect dynamic co-expression interactions involved in CRSwNP. In this approach, the internal evolution of the co-expression relation between a pair of genes (X, Y) was captured under a change in the expression profile of a third gene (Z), named the switch gene. Subsequently, the biological relevancy of the statistically significant triplets was confirmed using both gene set enrichment analysis and gene regulatory network reconstruction. Finally, the importance of identified switch genes was confirmed using a random forest model. The results suggested four dysregulated pathways in CRSwNP, including "positive regulation of intracellular signal transduction", "arachidonic acid metabolic process", "spermatogenesis" and "negative regulation of cellular protein metabolic process". Additionally, the S100a9 as a switch gene together with the gene pair {Cd14, Tpd52l1} form a biologically relevant triplet. More specifically, we suggested that S100a9 might act as a potential upstream modulator in toll-like receptor 4 transduction pathway in the major CRSwNP pathologies.

The cyclooxygenase-2 upregulation mediates production of PGE2 autacoid to positively regulate interleukin-6 secretion in chronic rhinosinusitis with nasal polyps and polyp-derived fibroblasts.

Chronic rhinosinusitis (CRS) can be traditionally classified as CRSwNP [with nasal polyps (NPs)] and CRSsNP (without NPs) based on the clinical phenotypes but recently suggested to be classified by the endotypes. We have identified overexpression of the cyclooxygenase-2 (COX-2) gene in NP tissues of Taiwanese CRSwNP patients. Therefore, in this study, we sought to investigate its protein expression/location/distribution in NP specimens and explore its roles in nasal polyposis. The COX-2 protein and mRNA expression was found higher in NPs than that in the control and CRSsNP patients' nasal tissues, mainly located at the epithelium and subepithelial stroma. Consistently, the CRS-related peptidoglycan (PGN) and bradykinin provoked COX-2 mRNA and protein upregulation in the human NP-derived fibroblasts and caused PGE2, thromboxane A2 (TXA2), and interleukin (IL-6) secretion in culture medium. Further analysis revealed that the PI3K/Akt activation and COX-2 induction were necessarily required for PGN-induced IL-6 production/secretion and the induced PGE2, but not TXA2, was speculated to affect IL-6 protein trafficking and production. Finally, the IL-6 increase observed in vitro could also be detected in NP tissues. Collectively, we demonstrated here that COX-2 protein and IL-6 are overexpressed in human NP tissues. In response to PGN challenge, the PI3K/Akt activation and COX-2-mediated PGE2 autacoid correlates with extracellular IL-6 protein trafficking/production in NP-derived fibroblasts, which can additionally contribute to the production of Th17-related cytokines such as IL-17 and TNF-α. This study also suggests COX-2 as a special biomarker for CRSwNP endotyping and may highlight the importance of COX-2 inhibitors in treating CRSwNP.

Identification of core gene in chronic rhinosinusitis with nasal polyps and correlations with inflammation-related genes.

OBJECTIVE: Our aim in this study is to identify the core genes of chronic rhinosinusitis with nasal polyps and analyze the correlations between it and inflammation-related genes. METHODS: GSE72713 dataset containing gene expression data of ECRSwNP, nonECRSwNP and healthy samples was obtained from Gene Expression Omnibus (GEO) and filtered by limma to identify DEGs among three groups, then the functions and correlated pathways of DEGs were analyzed using GO and KEGG. The core DEGs were selected by the intersection of DEGs and the PPI network was constructed via STRING. The correlations between the expression levels of CRSwNP core gene and inflammation-related genes were analyzed via the Mann-Whitney U test. RESULTS: The DEGs among ECRSwNP, nonECRSwNP, and CTRL were filtered respectively, and enrichment analysis showed they were associated with olfaction and/or immune responses. The PPI network was constructed by 7 core DEGs obtained via the intersection among three groups, and ALOX15 was confirmed as the core gene in the network. Subsequently, the correlations between the expression levels of ALOX15 and inflammation-related genes were illustrated. CONCLUSION: In this study, the core gene ALOX15 was selected from the DEGs among ECRSwNP, nonECRSwNP, and CTRL. IL5, IL1RL1, and IL1RAP were found to exhibit a significant positive correlation with ALOX15. LEVEL OF EVIDENCE: Level 3.

Chronic Rhinosinusitis-Microbiological Etiology, Potential Genetic Markers, and Diagnosis.

Chronic rhinosinusitis (CRS) is a significant public health problem. Bacterial colonization and impaired mucociliary clearance play a significant role in the inflammatory process. Several inflammatory pathways and host defense elements are altered in CRS, which may contribute to observed differences in the microbiome. To date, researching CRS has been difficult due to limited access to the studied tissue and a lack of available biomarkers. Ongoing scientific research is increasingly based on simple and objective analytical methods, including sensors, detection with PCR, and sequencing. Future research on microbiota and human factors should also include genomics, transcriptomics, and metabolomics approaches. This report analyzes the changes that occur in the paranasal sinuses of people with acute and chronic rhinosinusitis, the composition of the microbiota, the human genetic markers that may shed light on the predisposition to CRS, and the advantages and disadvantages of classical and molecular diagnostic methods, as well as addressing the difficulties of sinusitis treatment.

Gut microbiota and chronic rhinosinusitis: a two-sample Mendelian randomization study.

BACKGROUND: The nasal cavity and gut are interconnected, both housing a rich natural microbiome. Gut microbiota may interact with nasal microbiota and contribute to the development of chronic rhinosinusitis (CRS). However, the specific role of gut microbiota in CRS has not been fully investigated. Therefore, we conducted a two-sample Mendelian randomization study to reveal the potential genetic causal effect of gut microbiota on CRS. METHODS: We performed a two-sample Mendelian Randomization (MR) analysis using aggregated data from genome-wide association studies (GWAS) on gut microbiota and CRS. The primary method used to assess the causal relationship between gut microbiota and CRS was the inverse variance weighting (IVW) method. In addition, sensitivity analyses were conducted to evaluate the robustness of the MR results, including heterogeneity, pleiotropy, and leave-one-out tests. RESULTS: Genetically predicted twelve gut microbiota, including class Coriobacteriia, class Methanobacteria, family Coriobacteriaceae, family Methanobacteriaceae, family Pasteurellaceae, genus Haemophilus, genus Ruminococcus torques group, genus Subdoligranulum, order Coriobacteriales, order Methanobacteriales, order Pasteurellales, and phylum Proteobacteria, demonstrated a potential inhibitory effect on CRS risk (P < 0.05). In addition, four gut microbiota, including family Streptococcaceae, genus Clostridium innocuum group, genus Oscillospira, and genus Ruminococcaceae NK4A214 group, exhibited a causal role in increasing CRS risk (P < 0.05). Sensitivity analyses showed no evidence of heterogeneity or pleiotropy (P > 0.05). CONCLUSIONS: This study reveals the causal relationship between specific gut microbiota and CRS, which provides a new direction and theoretical foundation for the future development of interventions and prevention and treatment strategies for CRS.

Identification of Pyroptosis-Related Genes Regulating the Progression of Chronic Rhinosinusitis with Nasal Polyps.

INTRODUCTION: Chronic rhinosinusitis with nasal polyps (CRSwNP) is an immunologic disease, and pyroptosis, an inflammation-based cellular death, strictly modulates CRSwNP pathology, whereas the pyroptosis genes and mechanisms involved in CRSwNP remain unclear. Herein, we explored disease biomarkers and potential therapeutic targets for pyroptosis and immune regulation in CRSwNP using bioinformatics analysis and tissue-based verification. METHODS: We retrieved the transcriptional profiles of the high-throughput dataset GSE136825 from the Gene Expression Omnibus database, as well as 170 pyroptosis-related gene expressions from GeneCards. Using R, we identified differentially expressed pyroptosis-related genes and examined the potential biological functions of the aforementioned genes using Gene Ontology, Kyoto Encyclopedia of the Genome pathway, immune infiltration, and protein-protein interaction (PPI) network analyses, thereby generating a list of hub genes. The hub genes were, in turn, verified using real-time quantitative polymerase chain reaction (qRT-PCR), immunohistochemistry (IHC), and Western blotting (WB). Ultimately, using the StarBase and miRTarBase databases, we estimated the targeting microRNAs and long chain non-coding RNAs. RESULTS: We demonstrated that the identified pyroptosis-related genes primarily modulated bacterial defense activities, as well as inflammasome immune response and assembly. Moreover, they were intricately linked to neutrophil and macrophage infiltration. Furthermore, we validated the tissue contents of hub genes AIM2, NLPR6, and CASP5 and examined potential associations with clinical variables. We also developed a competitive endogenous RNA (ceRNA) modulatory axis to examine possible underlying molecular mechanisms. CONCLUSION: We found AIM2, CASP5, and NLRP6, three hub genes for pyroptosis in chronic rhinosinusitis with nasal polyps, by biological analysis, experimental validation, and clinical variable validation.

Gastroesophageal Reflux and Chronic Rhinosinusitis: A Mendelian Randomization Study.

OBJECTIVE: Chronic rhinosinusitis (CRS) is associated with gastroesophageal reflux (GERD). However, the causal relationship is controversial. We conducted a two-sample Mendelian Randomization (MR) analysis to explore this potential association. METHODS: Based on genome-wide association studies (GWAS), a univariable MR was performed to explore the causal relationship of GERD with CRS. Instrumental variables (IVs) pertinent to anti-GERD treatment were employed as a means of validation. The primary MR outcome was established using an inverse variance weighted (IVW) method, supplemented by multiple sensitivity analyses. Subsequently, a multivariable MR was conducted to account for potential confounding variables, thereby ascertaining a direct effect of GERD on CRS. Finally, a network MR analysis was carried out to elucidate the mediating role of asthma in the relationship between GERD and CRS. RESULTS: The univariable MR demonstrated an association between GERD and an elevated risk of CRS (IVW OR = 1.30, 95% CI = 1.18-1.45, p = 4.19 × 10-7). Omeprazole usage was associated with a reduction in CRS risk (IVW OR = 0.64, 95% CI = 0.42-0.98, p = 0.039). The causal relationship between GERD and CRS remained after adjusting for potential confounders, such as smoking characteristics, body mass index, asthma, allergic rhinitis, in the multivariable MR analysis. Besides, the proportion of the causal effect of GERD on CRS mediated by asthma was 19.65% (95% CI = 2.69%-36.62%). CONCLUSION: GERD was independently associated with an increased risk of CRS. The mediating role of asthma between GERD and CRS also reveals that GERD is one of the mechanisms underlying unified airway disease. LEVEL OF EVIDENCE: 3 Laryngoscope, 134:3086-3092, 2024.

Single-cell RNA sequencing reveals the epithelial cell, fibroblast, and key gene alterations in chronic rhinosinusitis with nasal polyps.

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a chronic inflammatory disease of the nasal mucosa, and epithelial-mesenchymal transition (EMT) is thought to be an essential process in the pathogenesis of CRSwNP. However, the mechanisms of epithelial and fibroblastic changes at the single-cell level are unclear. In this study, we investigated the epithelial cell, fibroblast, and key gene alterations in the development of CRSwNP. We revealed major cell types involved in CRSwNP and nasal mucosal inflammation formation, then mapped epithelial and fibroblast subpopulations. We showed that the apical and glandular epithelial cells and the ADGRB3+ and POSTN+ fibroblasts were the key cell subtypes in the progression of CRSwNP. Pseudotime and cell cycle analysis identified dynamic changes between epithelial cells and fibroblasts during its development. WFDC2 and CCL26 were identified as the key marker genes involved in the development of CRSwNP and were validated by IHC staining, which may provide a potential novel target for future CRSwNP therapy. ScRNA-seq data provided insights into the cellular landscape and the relationship between epithelial cells and fibroblasts in the progression of CRSwNP. WFDC2 and CCL26 were identified as the key genes involved in the development of CRSwNP and may be the potential markers for gene therapy.

The inflammatory microenvironment of nasal polyps in patients with chronic rhinosinusitis and the relationship of this microenvironment with the nasal microbiome.

BACKGROUND: We investigated the characteristics of the microbial community of the nasal sinuses in patients with chronic rhinosinusitis with nasal polyps (CRSwNP) and identified the correlations of the nasal microbiome with the inflammatory microenvironment of the nasal cavity. METHODOLOGY: We collected matched nasal secretion and polyp tissue samples from 77 CRSwNP patients. Then, we extracted microbial DNA from cotton swabs, used high-throughput sequencing technology based on 16S ribosomal RNA (rRNA) to detect the bacterial community composition, and detected cytokines such as interleukin (IL)-5, IL-8, IL-17a, IL-17e, IL-18, IL-27 and interferon (INF)-gamma in the polyp tissue samples using Luminex. Eosinophils and neutrophils in the peripheral blood and polyp tissue were counted, and the relationships between inflammatory factors or inflammatory cell counts and nasal microbial diversity were analyzed. RESULTS: Among the inflammatory factors evaluated, IL-5 had a positive rate of 32.47%, IFN-γ had a positive rate of 84.42%, IL-17A and IL-17E had positive rates of 75.32%, IL-18 had a positive rate of 94.81%, IL-27 had a positive rate of 68.83%, and IL-8 had a positive rate of 100%. IL-17a and IL-27 were negatively correlated with both Enterobacter and Anaerococcus, IL-8 was negatively correlated with both Enterobacter and Staphylococcus, IL-18 was positively correlated with Candidatus Arthromitus and negatively correlated with Haemophilus, and IL-27 was positively correlated with Faecalibaculum. Lactobacillus and Enterococcus were positively correlated with the degree of neutrophil infiltration in nasal polyp tissue. CONCLUSIONS: In Southwest China, inflammation of the nasal polyps exhibits a variety of patterns. Enterobacteria and anaerobic bacteria may be correlated with the inflammatory pattern of nasal polyps. The neutrophil-mediated inflammatory response plays an important role in patients with CRSwNP in Southwest China.

sPLA2GIB Promotes PGD2 and IL-13 Production in Eosinophilic Chronic Rhinosinusitis with Nasal Polyps.

OBJECTIVE: Secreted phospholipase A2 Group IB (sPLA2GIB) regulates the release of arachidonic acid, prostaglandins, and other inflammatory lipid mediators. Although it has been well involved in extensive inflammatory diseases, its specific mechanism in chronic rhinosinusitis with nasal polyps (CRSwNP) remains unclear. In this study, we investigated the role of sPLA2GIB in the pathophysiology of CRSwNP. METHODS: Quantitative PCR, immunofluorescence staining, western blotting, and enzyme-linked immunosorbent assay (ELISA) were used to analyze the expression of sPLA2s, phospholipase A2 receptor (PLA2R), and prostaglandin D2 (PGD2) in nasal samples. Human nasal epithelial cells (HNECs) were cultured at an air-liquid interface (ALI) and stimulated with various cytokines. The human mast cell line HMC-1 was stimulated with sPLA2GIB, and the expression of PGD2 and cytokines in the culture supernatant was detected by ELISA. RESULTS: The mRNA and protein levels of sPLA2GIB were significantly higher in eosinophilic CRSwNP than in control tissues. sPLA2GIB was predominantly expressed in the nasal epithelial cells. PLA2R mRNA and protein levels were upregulated in both eosinophilic and non-eosinophilic CRSwNP compared with the control groups. IL-4, IL-13, TNF-α, and IL-1ß upregulated the expression of sPLA2GIB in ALI-cultured HNECs. sPLA2GIB induced PGD2 and IL-13 production in HMC-1 cells in a hydrolytic activity-independent manner. PGD2 protein expression was elevated in tissue homogenates of eosinophilic CRSwNP, and PGD2 upregulated the expression of IL-13 in HMC-1 cells. CONCLUSION: Increased secretion of sPLA2GIB by epithelial cells may promote eosinophilic inflammation in CRSwNP by enhancing PGD2 and IL-13 production in mast cells via binding to PLA2R. LEVEL OF EVIDENCE: N/A Laryngoscope, 134:1107-1117, 2024.

Inflammatory endotypes of adenoidal hypertrophy based on a cluster analysis of biomarkers.

OBJECTIVE: To identify adenoid inflammatory endotypes based on inflammatory markers, match endotypes to phenotypes, and predict endotypes. METHODS: This cross-sectional study included 72 children with adenoid hypertrophy. Thirteen inflammatory markers and total immunoglobulin E (TIgE) in adenoid tissue were analyzed using Luminex and enzyme-linked immunosorbent assay (ELISA) for performing cluster analysis. Correlation analysis was used to examine the characteristics of each cluster. Receiver operating characteristic (ROC) curve analysis was performed to screen for preoperative characteristic data with predictive value for adenoid inflammation endotype. RESULTS: The patients were divided into four clusters. Cluster 1 exhibited non-type 2 signatures with low inflammatory marker concentrations, except for the highest expression of Th1-related cytokines. Cluster 2 showed a non-type 2 endotype with the highest concentration of interleukin (IL)-17A and IL-22. Cluster 3 exhibited moderate type 2 inflammation, with the highest concentration of neutrophil factors. Cluster 4 demonstrated significant type 2 inflammation and moderate neutrophil levels. The proportions of AR and serum TIgE levels increased from clusters 1 to 4, and there was a gradual increase in the prevalence of chronic sinusitis from low to high neutrophilic inflammation. The area under the ROC curve for serum TIgE was higher than those for combined or other separate preoperative characteristics for predicting non-type 2 and type 2 inflammation in the adenoid tissue. CONCLUSIONS: The evaluation of cytokines in adenoid tissue revealed four endotypes. Serum TIgE level was an important indicator of the endotype of adenoid inflammation. Identification of adenoid inflammatory endotypes can facilitate targeted treatment decisions.

The current findings in eosinophilic chronic rhinosinusitis.

Chronic rhinosinusitis (CRS) is a persistent inflammatory disease of the nasal cavity and paranasal sinuses. Traditional classification is denoted by the presence (CRSwNP) or absence of nasal polyps (CRSsNP). Particularly, CRSwNP is distinguished by the presence of infiltrating cells and inflammatory markers in the nasal mucosa. Patients with CRSwNP in Western countries predominantly display a type 2 endotype, whereas those in Asian regions display a mixed type 2 endotype. Nevertheless, recent transcriptome analyses have revealed two types of nasal polyps - type 2 and non-type 2 polyps, suggesting that geographical differences in endotypes likely resulted from the different proportions of each endotype. Moreover, various endotypes of CRSsNP have been identified, making phenotype a crucial factor for predicting treatment efficacy. Type 2 endotypes, designated as eosinophilic CRS (ECRS) in Japan, are characterized by severe eosinophilic infiltration into the paranasal sinus tissue and are particularly refractory. In this review, we discuss the latest developments in ECRS. We also provide recent findings on the involvement of nasal epithelial cells in pathogenesis.