AbstractBackgroundChronic rhinosinusitis with nasal polyps (CRSwNP) was potentially due to the epithelial barrier injury. YES‐associated protein (YAP) is a multifunctional transcriptional factor and plays versatile roles in the regulation and maintenance of epithelial barrier in different organs and tissues. The purpose of this study is to elucidate possible effect and mechanism of YAP on the epithelial barrier of CRSwNP.MethodsPatients were divided into CRSwNP group (n= 12) and control group (n= 9). The location of YAP, PDZ‐binding transcriptional co‐activator (TAZ), and Smad7 were estimated by immunohistochemistry and immunofluorescence. Meanwhile, the expression of YAP, TAZ, Zona occludens‐1 (ZO‐1), E‐cadherin, and transforming growth factor‐beta1 (TGF‐β1) were detected by Western blot. After primary human nasal epithelial cells were treated with YAP inhibitor, the expression level of YAP, TAZ, ZO‐1, E‐cadherin, TGF‐β1, and Smad7 were measured by Western blot.ResultsCompared with the control group, the protein levels of YAP, TAZ, and Smad7 were significantly upregulated, while TGF‐β1, ZO‐1, and E‐cadherin were downregulated in CRSwNP. YAP and Smad7 demonstrated lower levels, while the expression of ZO‐1, E‐cadherin, and TGF‐β1 rose slightly after YAP inhibitor treatment in primary nasal epithelial cells.ConclusionsHigher level of YAP may lead to CRSwNP epithelial barrier injury via the TGF‐β1 signaling pathway, and the inhibition of YAP can partially reverse epithelial barrier function.