title: A time course study on the development of allergen-induced nasal airway remodeling in a rat model.
abstract: BACKGROUND
  Only a few studies have investigated the airway remodeling process in allergic rhinitis (AR), and the results reported are conflicting. We established an allergen-induced nasal remodeling model for AR using brown Norway rats and investigated time-dependent histological  changes and the reversibility of the epithelial and subepithelial changes.
  
  
  METHODS
  Ovalbumin (OVA)-sensitized rats were exposed to OVA daily and then assigned to one of five groups depending on the duration of the challenge. Groups I, II, III, and IV rats were exposed  for 1, 4, 8, and 12 weeks, respectively. Group V rats were exposed for 12 weeks and then protected from challenge for 4 weeks. Matched control rats were exposed to saline. Histological parameters of the nasal mucosa such as epithelial and subepithelial thickness, goblet cell hyperplasia, eosinophil  infiltration, submucosal gland hypertrophy, and expression of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) were compared between groups.
  
  
  RESULTS
  Repeated challenges for 12 weeks resulted in the characteristic features of nasal  airway remodeling. All parameters except epithelial thickness increased markedly. Goblet cell hyperplasia and eosinophil infiltration decreased to control group levels after cessation of challenge for 4 weeks. Subepithelial changes such as subepithelial thickening, submucosal gland hypertrophy,  and increased expression of MMP-9 and TIMP-1 were still observed after 4 weeks without challenge.
  
  
  CONCLUSIONS
  Our results indicate that prolonged OVA challenge can induce nasal remodeling. Epithelial changes were minimal or absent after cessation of the challenge, but subepithelial  changes were resistant to reversal.
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, Dankook University College of Medicine, Cheonan, Korea.
authors.forename: Young-Jun
authors.initials: YJ
authors.lastname: Chung
authors.forename: Hyo Yeol
authors.initials: HY
authors.lastname: Kim
authors.forename: Seung-Kyu
authors.initials: SK
authors.lastname: Chung
authors.forename: Hun-Jong
authors.initials: HJ
authors.lastname: Dhong
mesh_terms: D056151:Airway Remodeling; D000485:Allergens / Q000276:immunology*; D000818:Animals; D020780:Matrix Metalloproteinase 9 / Q000032:analysis; D023421:Models, Animal; D009297:Nasal Mucosa / Q000473:pathology*; D010047:Ovalbumin / Q000276:immunology; D051381:Rats; D011914:Rats, Inbred BN; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000032:analysis
chemical_list: D000485:Allergens; D019715:Tissue Inhibitor of Metalloproteinase-1; D010047:Ovalbumin; D020780:Matrix Metalloproteinase 9