The differences between sinonasal respiratory epithelial adenomatoid hamartoma and nasal polyps: insights into immunopathology

Background: : Respiratory epithelial adenomatoid hamartoma (REAH) is a benign lesion commonly occurring in the nasal cavity and sinuses. It is often accompanied by nasal polyps (NP). While the histological features of these two conditions have been studied, there is limited knowledge about their differences in the underlying immunopathology. Methods: : Nasal tissue specimens were collected from 8 patients with concurrent REAH and NP and 10 controls. The expression levels of inflammatory cytokines, tight junctions (TJ), and epithelial-mesenchymal transition (EMT)- related factors in the tissues were analyzed. The mRNA expression of the aforementioned factors was measured using qRT-PCR, while the expression of TJ and EMT-related proteins was analyzed through Western blotting and immunohistochemistry. Results: : Compared to the control group, levels of inflammatory cytokines (IFN-gamma, IL-5, IL-17A, IL-31, IL-33, and TNF-alpha) and EMT-related factors (alpha-SMA, COL1A1, MMP9, TGF-(31, and Vimentin) were significantly increased in both REAH and NP tissues. Conversely, E-Cadherin and TJ-related factors (Claudin-4 and Occludin) significantly decreased. When comparing REAH with NP, it was observed that the expression of IL-4, IL-5, and IL-33 was lower in REAH, while TNF-alpha was higher. Regarding TJ-related factors, the expression of Occludin was lower in REAH. Furthermore, in terms of EMT-related factors, except for E-Cadherin, the expressions of alpha-SMA, COL1A1, CTGF, MMP9, TGF-(31, and Vimentin were higher in REAH. Conclusion: : REAH and NP exhibit different immunopathological mechanisms. NP demonstrates a more severe inflammatory response, whereas REAH is characterized by a more pronounced TJ and EMT breakdown than NP.