Mucosal expression of aquaporin 5 and epithelial barrier proteins in chronic rhinosinusitis with and without nasal polyps

ObjectivesThe purpose of this study is to characterize the association between altered epithelial barrier function, represented by changes in histology and differential expression of the mucosal water membrane permeability protein aquaporin 5 (AQP5), and the pathophysiology of chronic refractory sinusitis (CRS) in patients with and without nasal polyposis.Study designProspective clinical study.SettingTertiary rhinology referral center.ParticipantsSinonasal samples were obtained from seven CRS subjects with nasal polyps (CRSwNP), seven CRS without nasal polyposis (CRSsNP), and five control healthy patients.MethodsMucosal membrane changes were evaluated through hematoxylin and eosin staining of the membrane barrier and immunohistochemical staining of AQP5 expression, a membrane channel protein that affects trans-epithelial water permeability and tissue edema. AQP5 expression was confirmed by real-time PCR (rt-PCR) and western blot. Levels of other membrane proteins, including E-cadherin and Septin-2, were also assessed.ResultsCRSwNP patients showed substantial histologic evidence of membrane remodeling with increased edema and glandular hyperplasia. The epithelial expression of AQP5 was significantly lower in CRSwNP as compared to CRSsNP or control. There was no significant difference in the expression of E-cadherin and Septin-2.ConclusionsCollectively, these data suggest that the mucosal epithelial barrier is compromised in the context of CRS (predominantly in CRSwNP) when compared to control and that AQP5 acts as a key tight junction protein in the maintenance of mucosal water homeostasis. We hypothesize that AQP5 plays a possible role in the pathophysiology of mucosal edema and polyp formation.