Nasal polyp (NP) is a common chronic inflammatory disease of the nasal cavity and sinuses.Although some authors have suggested that NP is related to inflammatory factors such as interleukin (IL)-1β,IL-5,IL-8,granulocyte-macrophage colony-stimulating factor (GM-CSF),tumor necrosis factor (TNF)-α,and IL-17,the mechanisms underlying the pathogenesis and progression of NP remain obscure.This study investigated the expression and distribution of IL-17 and syndecan-1 in NP,and explored the roles of these two molecules in the pathogenesis of eosinophilic chronic rhinosinusitis with nasal polyps (Eos CRSwNP) and non-Eos CRSwNP.Real-time PCR and immunohistochemistry were used to detect the expression of IL-17 and syndecan-1 in samples [NP,unciform process (UP) from patients with CRS,and middle turbinate (MT) from healthy controls undergoing pituitary tumor surgery].The results showed that the expression levels of IL-17 and syndecan-1 were upregulated in both NP and UP tissues,but both factors were higher in NP tissues than in UP tissues.There was no significant difference in IL-17 levels between the Eos CRSwNP and non-Eos CRSwNP samples,and syndecan-1 levels were increased in the non-Eos CRSwNP tissues as compared with those in Eos CRSwNP tissues.In all of the groups,there was a close correlation between the expression of IL-17 and syndecan-1 in nasal mucosa epithelial cells,glandular epithelial cells,and inflammatory cells,suggesting that IL-17 and syndecan-1 may play a role,and interact with each other,in the pathogenesis ofnon-Eos CRSwNP.