Alteration in goblet cell numbers and mucin gene expression in a mouse model of allergic conjunctivitis

PURPOSE. To determine whether the number of filled conjunctival goblet cell s and mucin gene expression are altered in a mouse model of allergic conjun ctivitis. METHODS. A/J mice were sensitized intraperitoneally with cat dander or the peptide P3-1 from the protein Fel d1. Two weeks later, the mice were challe nged for 7 consecutive days with eye drops containing the allergens. Conjun ctival tissue was harvested at 0, 6, 24, or 48 hours after final antigen ch allenge. Control samples were naive animals and mice sensitized with cat da nder and challenged with OVA-peptide or PBS. The mean number of filled gobl et cells per square millimeter in three forniceal fields for each group was determined in wholemounts of conjunctiva prepared using rhodamine-phalloid in labeling followed by confocal microscopy. RNA was isolated from conjunct iva of the contralateral eye and taken for relative quantitation of mRNA of the goblet cell mucin Muc5AC and the epithelial membrane-spanning mucin Mu c4, by real-time RT-PCR. RESULTS. The number of filled goblet cells was significantly decreased with both cat dander and P3-1, after final ocular challenge (P < 0.001). The mo st significant decrease over naive mice was seen at 6 hours after final cha llenge with both allergens. The number of filled goblet cells was still dec reased but was returning toward naive levels at 24 hours (P < 0.05), and at 48 flours no significant difference was seen compared with naive, PBS-trea ted, and OVA-peptide-treated control samples. For both cat dander and P3-1, Muc5AC and Muc4 mRNA was found to be decreased at the time of final ocular challenge. The level of Muc5AC mRNA from goblet cells rebounded from the d ecrease to show an increase over control by 24 hours after final challenge, and by 48 hours, the mRNA level had returned to naive control range. In co ntrast, significant increases in Muc5AC mRNA were evident after final contr ol challenge with PBS or OVA-peptide, indicating a potential irritant effec t of drop application. The Muc4 mRNA level was significantly reduced at all time points except 24 hours after the last challenge. By comparison with a llergen-challenged eyes, no change in Muc4 message levels was noted at any time point in OVA-peptide- or PBS-treated control eyes. CONCLUSIONS. These findings demonstrate that, in the conjunctiva of mice, r epetitive application of allergens induces a reduction in the number of fil led goblet cells and a decrease in Muc5AC and Muc4 mRNAs. After a period of 24 to 48 hours, the goblet cell number return to naive levels, and goblet cell mucin mRNA levels return to above or within normal range, indicating a rapid recovery in the mucus secretion system.