Prostaglandin E Receptor 2 (EP2) Dysregulation in Allergic Fungal Rhinosinusitis Nasal Polyp Epithelium

Abstract

Objectives: Allergic fungal rhinosinusitis (AFRS) is an eosinophilic subtype of chronic rhinosinusitis with nasal polyposis (CRSwNP). This study aimed to investigate the transcriptome of AFRS nasal polyp epithelium.

Methods: Sinonasal epithelial cells were harvested from healthy nasal mucosa and polyp tissue collected from participants undergoing elective sinonasal surgery. Primary epithelial cells were subsequently grown in air/liquid interface and subjected to RNA-seq analysis, RT-qPCR, immunoblotting, and immunostaining.

Results: A total of 19 genes were differentially expressed between healthy and AFRS sample epithelium. The second top candidate gene, ranked by adjusted p-value, was prostaglandin E receptor 2 (PTGER2). The upregulation of PTGER2 was confirmed by RT-qPCR and immunoblot. The presence of the EP2 receptor, encoded by the PTGER2 gene, was confirmed by immunocytochemistry.

Conclusion: PTGER2 is a potential novel therapeutic target for AFRS. EP2 dysregulation is associated with aspirin-exacerbated respiratory disease, potentially giving insight into common mechanisms of disease in severe CRSwNP.

Level of evidence: NA Laryngoscope, 135:S1-S8, 2025.

Keywords: allergic fungal sinusitis; eicosanoid receptor; nasal polyposis; prostaglandin E receptors.

Fig. 1

Clinical characteristics of AFRS. High‐resolution coronal CT with bone window demonstrating characteristic AFRS features. Unilateral disease presentation following prior endoscopic sinus surgery highlights unique presentation with the potential to advance from one sinonasal region to another. Expansion of sinonasal cavities with thickened mucosa (arrows) and dense concretions (asterisks) (A). Eosinophilic, allergic‐type mucin in AFRS. Formation of compact‐layered aggregates of mucin and inflammatory cells and debris are characteristic findings. Fungal elements present in extracellular mucin (arrowheads) (B). Hematoxylin and eosin stain, 200× magnification. Inset: Walls of fungal hyphae appear black when stained with Grocott methenamine silver stain (GMS). GMS stain, 400× magnification. CT, computed tomography.

Fig. 2

Cell culture model at air/liquid interface. Illustration depicting culture conditions of primary sinonasal epithelial cells. Cells were grown in flasks containing conditional reprogramming culture (CRC) media and a feeder layer of irradiated 3T3 fibroblasts to promote basal cell expansion (A‐left). Next, the basal cells were transferred to collagen (yellow)‐coated transwell permeable supports and grown at air/liquid interface (ALI) for 14 days to promote differentiation (A‐right). Widefield image of epithelial cell colonies in CRC conditions (B‐left). Dotted circle denotes epithelial cell colony. Image of multiciliated cells (red) present in ALI cultures (B). MCC = multi‐ciliated; MP = mucus producing.

Fig. 3

Differential gene expression analysis of RNA‐seq data. Volcano plot showing differentially expressed genes by fold change and q‐value (adjusted p‐value). Dotted lines indicate threshold values. The genes selected as differentially expressed are in red. n = 5 healthy and 4 AFRS samples.

Fig. 4

Expression levels of genes differentially expressed in AFRS. Heatmap representation of genes dysregulated in AFRS. Polyp samples are denoted as P1–P4 and healthy samples as H1–H5. The genes are ranked by adjusted p‐value (A). List of the 19 genes differentially expressed between healthy and AFRS samples (B). n = 5 healthy and 4 AFRS samples.

Fig. 5

PTGER expression in healthy, AFRS, and AERD sinonasal epithelial cells. RT‐qPCR analysis of PTGER1‐4 mRNA levels in healthy (blue), AFRS (red), and AERD (gray) sinonasal epithelial cells grown at ALI (A–C). n = 3–4 participant samples per cohort. Data are represented as mean ± standard deviation. Kruskal–Wallis test. **p < 0.01.

Fig. 6

EP2 expression and protein localization in healthy and AFRS sinonasal epithelium. Immunoblots showing EP2 and actin (loading control) in healthy and AFRS sinonasal epithelial cells grown at ALI (A). EP2 levels were significantly increased in AFRS compared with healthy control samples (B). EP2 values were normalized to actin. n = 4 participant samples. Data are represented as mean ± standard deviation. Mann–Whitney test. *p < 0.05. Immunostained healthy (top) and AFRS (middle) sinonasal epithelial cells shows localization of EP2 (green) and nuclei (blue) (C). The secondary‐only negative control shows background staining. Arrow indicates perinuclear staining. Box indicates area magnified. Scale bar is 20 μm. n = 3 participant samples.