OBJECTIVETo explore the feature of nasal mucosa remodeling in experimental allergic rhinitis.

METHODSTwenty-four male Hartley guinea pigs (4 weeks, 250 -300 g) were randomly divided into four groups (control group and allergen exposure groups 1 - 3), each group had 6 guinea pigs. Allergen exposure animals were sensitized by intraperitoneal (ip) injection of ovalbumin (OVA). Sensitized guinea pigs were subjected to either brief or prolonged exposure to allergen. Both brief exposure group (allergen exposure groups) and prolonged exposure group (allergen exposure group 2 and 3) received a daily intranasal challenge with 5% OVA in 0.9% saline from Day 22 to Day 28, the prolonged exposure group (allergen exposure group 2 and 3) followed by twice weekly exposure to 5% OVA intranasal for an additional 8 and 12 weeks respectively. Control animals were given saline only. At 24 h after the last intranasal challenge, the guinea pigs were killed and the heads of the animals were removed and fixed in 10% neutral buffered formalin for 24 hours, then decalcified in 5% trichloroacetic acid for 10 days. The tissue blocks were embedded in paraffin. The paraffin sections 3 microm thick were stained with hematoxylin and eosin (HE), alcian blue (pH, 2. 6)-periodic acid-Schiff (AB-PAS), and Masson's Trichrome (MT). The infiltrating eosinophils in nasal mucosa were examined, AB-PAS-positive cells in the surface epithelium in nasal septal mucosa were counted. The percentage area of MT stained extracellular matrix in septal mucosa and conchae and damage of epithelium were determined by an image analyzer.

RESULTSThe control group only presented a few eosinophils. Significant eosinophil infiltration was observed in the sensitized groups. Compared with control group (intact epithelium 87.7% +/- 11.1%), there was no significant epithelial damage in 1 week exposure group. Significant epithelial damage were observed in 8 and 12 weeks groups (intact epithelium 36.7% +/- 16.9%, 37.9% +/- 12.9%, respectively). An increase in AB-PAS-positive cells was observed in the mucosa of nasal septum in the prolonged allergen exposure groups, but not in the brief allergic inflammation group in comparison with the control. The brief OVA exposure group did not show increased collagen fibrils within the mucosa of nasal septum and conchae. In contrast, after prolonged OVA exposure an increase in matrix was observed. Furthermore, in both the nasal septum and conchae, significant increasing of ECM deposition was found in a further prolonged exposure for 12 weeks compared to 8 weeks.

CONCLUSIONSEpithelial damage, goblet cells hyperplasia and extracellular matrix deposition were observed as the features of remodeling in this guinea pig model of allergic rhinitis.