Histological and immunological observations of bacterial and allergic chronic rhinosinusitis in the mouse.

Background: The purpose of this study was to elucidate histological and immunologic features of mouse models of bacterial chronic rhinosinusitis (BCRS) and allergic chronic rhinosinusitis (ACRS).

Methods: A BCRS mouse model was established using Streptococcus pneumoniae inoculation plus Merocel (Medtronic, Jacksonville, FL) ostiomeatal obstruction for 12 weeks. An ACRS mouse model was developed by means of ovalbumin (OVA) i.p. injection and subsequent repeated OVA intranasal challenge for 12 weeks. Histological changes of sinonasal mucosa of both models were examined by means of hematoxylin and eosin staining for general morphology and inflammatory cell, periodic acid-Schiff staining for goblet cell, and Masson-trichrome staining for collagen. Enzyme-linked immunosorbent assay was used to detect the concentrations of various cytokines in nasal lavage fluid.

Results: Polymorphonuclear neutrophil infiltration in lamina propria was more obvious in the BCRS model, whereas eosinophil infiltration was more apparent in the ACRS model. Significant goblet cell and subepithelial gland hyperplasia, subepithelial fibrosis, epithelial thickening, and mononuclear cell infiltration were shown in both models with more severe extent found in the ACRS model. Interleukin (IL)-6 and tumor necrosis factor alpha levels in NLF from both models were increased and peaked at 1 week. Interferon gamma levels were also up-regulated in both models but reached maximum at 1 week in the BCRS model and 4 weeks in the ACRS model. IL-8 (CXCL8) levels were only increased in BCRS mice and peaked at 1 week, whereas IL-5, IL-13, and eotaxin (CCL11) levels were only enhanced in ACRS mice and peaked at 1 week. The Th1/Th2 ratio in BCRS mice was significantly higher than that in ACRS mice (6.68 +/- 2.33 versus 1.37 +/- 0.86; p < 0.01).

Conclusion: Histological and immunologic features of BCRS and ACRS mouse models were similar to those of human noneosinophilic and eosinophilic CRS, respectively. BCRS and ACRS mouse models have distinct immunologic characteristics and are applicable for CRS research.