Effects of Minimal Persistent Inflammation on Nasal Mucosa of Experimental Allergic Rhinitis

BACKGROUND: Minimal persistent inflammation (MPI) is considered another piece of the complex puzzle of allergic inflammation. Although some studies regarding MPI have been reported, no study has evaluated the effects of MPI on the structure changes at the site of allergic reaction. This study investigates whether long-time MPI during allergic rhinitis (AR) results in some features of tissue remodeling in the nasal mucosa. METHODS: An animal model of MPI was developed by repeated nasal challenge with low concentration of ovalbumin (OVA) in sensitized guinea pigs. The models were assessed by allergic symptom after antigen challenge, eosinophil infiltration in the nasal mucosa, and intercellular adhesion molecule (ICAM) 1 expression on nasal epithelial cells. The histopathological changes in nasal mucosa were determined by Alcian blue-periodic acid-Schiff and Masson's trichrome staining. The expression of transforming growth factor (TGF) beta(1) and matrix metalloproteinase (MMP) 9 was examined by immunofluorescence under a confocal laser scan microscope. RESULTS: When sensitized animals were challenged with the low concentration of 0.01% OVA, the symptom of sneezing disappeared, but there were still mild eosinophils infiltration and weak ICAM-1 expression, which indicated the success of MPI models. Moreover, the number of goblet cells and the percentage area of collagen deposition were both mildly increased. The expression of MMP-9 and TGF-beta(1) was also weakly elevated. CONCLUSION: We have successfully established MPI models and proved long-time MPI may result in mild features of remodeling in the nasal mucosa, which provide new insights into the unexpected potential effects of MPI on the structural changes.