Features of mesenchymal transition in the airway epithelium from chronic rhinosinusitis

Background Chronic rhinosinusitis (CRS) defines a group of disorders characterized by persistent inflammation of the sinonasal tract. Epithelial changes and structural remodelling are present, but whether epithelial differentiation is altered remains uncertain. Methods To evaluate the differentiation state of the sinonasal epithelium in CRS, sinonasal biopsies from patients with CRS with nasal polyps (CRSwNP) or CRS without nasal polyps (CRSsNP), or with allergic rhinitis (AR), as compared to controls, were processed by immunohistochemistry and RT‐qPCR for terminal differentiation (E‐cadherin, high molecular weight cytokeratins (Hmw CK) and CK5, vimentin) and lineage differentiation (ß‐tubulin IV+ ciliated cells, MUC5AC+ goblet cells, p63 + basal cells). Findings were correlated with subepithelial fibrosis and clinical CT score. Results Expression of E‐cadherin was decreased at protein and mRNA levels in CRSwNP and CRSsNP, as compared to controls. Staining for Hmw CKs was also reduced in CRSwNP and CRSsNP, and CK5 mRNA was decreased in CRSwNP. These features were not due to changes in lineage specification, but associated with increases in vimentin‐expressing epithelial cells. In addition, vimentin expression correlated with the basement membrane thickening and with CT score, as well as with tissue eosinophils. Conclusion Features of epithelial dedifferentiation towards a mesenchymal phenotype are observed in CRSwNP and CRSsNP and correlate with airway fibrosis and inflammation.