The pathogenesis of chronic rhinosinusitis (CRS) remains unclear to date. The tissue remodeling in nasal polyps may be the result of inflammatory mediators and may involve epithelial-mesenchymal transition (EMT) and EMT-associated features such as cell motility in nasal epithelial cells (NECs). We determined whether NEC in nasal polyps of CRS already display features of EMT in vivo or respond with EMT to growth factor stimulation in vitro. Nasal polyp tissues expressed both epithelial and mesenchymal markers. Primary NEC from inferior turbinates and nasal polyps responded to the EMT-inducing agents transforming growth factor (TGF)-β1 and epidermal growth factor (EGF) with different expression patterns of EMT markers (E-cadherin, N-cadherin, Snail, Slug, Twist), however, only NEC from nasal polyps were susceptible to TGF-β1 and EGF-dependent cell migration. Our data suggest that a partial EMT is associated with the pathogenesis of nasal polyps in CRS patients. Furthermore, we show for the first time that epithelial cells from both nasal polyps and inferior turbinates were able to undergo an EMT-like process following exposure to TGF-β1 or EGF in vitro but that only NEC from nasal polyps responded with enhanced cell motility. Our data suggest that NEC from CRS patients have undergo partial EMT and that this process may be involved in the pathogenesis of CRS.

The signaling pathways that sustain the disease process of chronic rhinosinusitis with nasal polyps (CRSwNP) remain poorly understood. We sought to determine the expression levels of Wnt signaling genes in CRSwNP and to study the role of the Wnt pathway in inflammation and epithelial remodeling in the nasal mucosa. Microarrays and real time-quantitative polymerase chain reaction comparing gene expression in matched NPs and inferior turbinates revealed that WNT2B, WNT3A, WNT4, WNT7A, WNT7B, and FZD2 were up-regulated and that FZD1, LRP5, LRP6, and WIF1 were down-regulated in NPs. Immunolabeling showed robust expression of Wnt ligands, nuclear β-catenin, and Axin-2 in NP tissue, suggesting that Wnt/β-catenin signaling is activated in NPs. We used primary human nasal epithelial cell (HNEpC) cultures to test the functional consequences of Wnt pathway activation. Monolayer HNEpCs treated with recombinant human WNT (rhWNT) 3A, but not with rhWNT4, had altered epithelial morphology and decreased adhesion, without loss of viability. We found that neither rhWNT3A nor rhWNT4 treatment induced proliferation. The expression and release of inflammatory cytokines IL-6 and granulocyte-macrophage colony-stimulating factor were increased after rhWNT3A exposure of HNEpCs. When differentiated at an air-liquid interface, rhWNT3A- and WNT agonist-, but not rhWNT4-treated HNEpCs, had abnormal epithelial architecture, failed to undergo motile ciliogenesis, and had defective noncanonical Wnt (planar cell polarity) signaling. On the basis of these results, we propose a model in which Wnt/β-catenin signaling sustains mucosal inflammation and leads to a spectrum of changes consistent with those seen during epithelial remodeling in NPs.

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a common disease that has a considerable impact on the quality of life. Alterations in signalling pathways may contribute to the ongoing inflammation and proliferation in CRSwNP. The MEK1/2-ERK1/2 pathway transmits signals from many extracellular molecules to regulate cellular processes. We examined tissue samples from nasal polyps and the inferior turbinate of patients with CRSwNP and the inferior turbinate from subjects with healthy mucosa. The expressions of MEK1/2, ERK1/2, and their active phosphorylated forms pMEK1/2 and pERK1/2 were analysed using DNA microarray, quantitative real-time PCR, protein array, Western hybridisation, and immunohistochemistry. We detected increased MEK1/2 protein expression in nasal polyps compared to the inferior turbinates of patients with CRSwNP or healthy mucosa. We also found a higher amount of MEK1/2 in the inferior turbinates of patients with CRSwNP compared to those with healthy mucosa. Most importantly, we observed a significant increase in the phosphorylation of MEK1/2 and ERK1/2 in nasal polyps compared to both types of controls. We observed activation of the MEK1/2-ERK1/2 pathway in nasal polyps. Interestingly, we did not see the same activation pattern in different tiers of the MEK1/2-ERK1/2 signalling cascade. One explanation for this result is that the components enhance the complex MEK-ERK cascade in a distinct manner, enabling a wide variety of functions. The MEK1/2-ERK1/2 pathway appears to play a pivotal role in the pathogenesis of CRSwNP.

Chronic rhinosinusitis with nasal polyps (CRSwNP) in Caucasians is a chronic Th2 inflammatory disease of the nasal and paranasal mucosa and the recruitment of leukocytes to the site of inflammation is poorly understood. We studied mRNA and protein expression profiles of adhesion molecules in nasal polyp and associated inferior turbinate tissues using molecular, biochemical, and immunohistological methods. Analysis showed a strongly decreased E-selectin expression in nasal polyps with a significant difference between eosinophil and neutrophil counts in nasal polyps and balanced counts in inferior turbinates. E-selectin expression is known to be downregulated in a Th2 milieu and has an essential role in immunosurveillance by locally activating neutrophil arrest and migratory function. A downregulation of E-selectin may come along with an immune imbalance in Caucasian nasal polyps due to a significant inhibition of neutrophil recruitment. Therefore, we suggest that an upregulation of E-selectin and the associated influx of neutrophils may play a significant role in the resolution of inflammation as well as for the pathophysiology of nasal polyps of Caucasian chronic rhinosinusitis patients.

Background: Chronic rhinosinusitis with nasal polyps (CRSwNP) is a multifactorial disease; the underlying mechanisms of cell signalling are not fully understood. STAT3 (signal transducer and activator of transcription 3) is a phosphokinase and a key signalling molecule implicated in cell cycle regulation. We studied the distribution and expression of STAT3 to examine the role of STAT3 in the pathogenesis of CRSwNP. Methods: We investigated tissue samples of the nasal polyps and inferior turbinate of patients with CRSwNP as well as samples of the inferior turbinate of subjects without chronic sinusitis. The expression levels of STAT3 and its activated form pSTAT3 were analysed using Western blotting, protein array, DNA microarray and immunohistochemistry. Results: No significant differences were found in STAT3-mRNA levels between the samples of nasal polyps and inferior turbinates of the same patient. However, the amount of pSTAT3 was increased in the polyp tissue compared to the inferior turbinates from both CRSwNP patients and control subjects (p < 0.01), indicating an activation of STAT3 in polyps. We identified a varying distribution pattern of pSTAT3; pSTAT3 was primarily found in superficial epithelial cells but not in the basal layer of the epithelium of the turbinate, whereas pSTAT3 was located in all layers of the epithelium of the polyp and mostly noted in the basal layer. Conclusions: Our results of the activation and varying localisation of STAT3 and its phosphorylated form in nasal polyps suggest that pSTAT3 plays a crucial role in the proliferative development of nasal polyps.