Background: The mechanisms that regulate epithelial integrity and repair in asthma are poorly understood. We hypothesized that allergen exposure could alter epithelial inflammation, damage and proliferation in atopic asthma.
Objective: We studied epithelial cell infiltration, shedding, expression of the proliferation marker Ki-67 and the epithelial cell-cell adhesion molecules Ep-CAM and E-cadherin in bronchial biopsies of 10 atopic mild asthmatics 48 h after experimental diluent (D) and allergen (A) challenge in a cross-over design.
Methods: Epithelial shedding, expressed as percentage of not intact epithelium, Ki-67+, eosinophil/EG-2+, CD4+ and CD8+ cells were quantified by image analysis in bronchial epithelium, and adhesion molecules were analysed semi-quantitatively.
Results: Epithelial shedding was not altered by A (D: 88.1+/-3.1% vs. A: 89.2+/-3.7%; P=0.63). The numbers of Ki-67+ epithelial (D: 10.2+/-0.2 vs. A: 19.9+/-0.3 cells/mm; P=0.03), EG-2+ (D: 4.3+/-0.5 vs. A: 27+/-0.3 cells/mm; P=0.04) and CD4+ cells (D: 1.7+/-1.2 vs. A: 12.3+/-0.6 cells/mm; P=0.04) were significantly increased after A, whilst CD8+ numbers were not significantly changed (P>0.05). E-cadherin and Ep-CAM epithelial staining showed a similar intensity after D and A (P>0.05). We found a positive correlation between EG-2+ and Ki-67+ cells in the epithelium (Rs: 0.63; P=0.02).
Conclusion: Our study indicates that allergen challenge increases epithelial proliferation in conjunction with inflammation at 2 days after exposure. This favours the hypothesis that long-lasting epithelial restitution is involved in the pathogenesis of asthma.