Quantitative expression of osteopontin in nasal mucosa of patients with allergic rhinitis: effects of pollen exposure and nasal glucocorticoid treatment

Subjects with AR were randomised to receive treatment with fluticasone propionate (FP) (n = 12) or a placebo (n = 16) over the grass pollen season and nasal biopsies were taken prior to, and during the season. OPN expression in the nasal mucosa was examined with immunohistochemistry. Healthy non-AR controls (n = 5) were used as a comparator.OPN expression was detected in epithelial cells, subepithelial infiltrating/inflammatory cells and cells lining the vessels and glands of all subjects. Comparison of the pre- and peak-pollen season biopsy sections in placebo treated patients revealed no increase in OPN expression during the grass pollen season (5.7% vs 6.4%). Treatment with a local glucocorticosteroid did not alter the expression of OPN during pollen exposure (6.2% vs 6.7%).OPN has been increasingly associated with the pathogenesis of various Th2-mediated diseases. However, our finding that the OPN expression in the nasal mucosa of AR patients is not significantly affected by allergen exposure and is comparable to that of the healthy controls, suggests that intracellular OPN is not directly involved in the pathogenesis of allergic rhinitis.The inflammatory process in allergic rhinitis (AR) involves many different inflammatory cells, cytokines, chemokines and other regulatory molecules [1]. It is well known that exposure to allergens, including natural pollen exposure, primarily enhances eosinophilic inflammation in the nose [2] and increases cytokine release [1]. Furthermore, local glucocorticoids are efficient in attenuating the allergen-induced inflammation and the cytokine expression, as we and others have documented in nasal mucosal studies [2-6].OPN is a pleiotropic cytokine normally expressed by many cell types [7], which has been implicated in various diseases [8], including asthma [9-11] and chronic rhinosinusitis [12]. OPN can be expressed in eosinophils, which could argue its involvement in allergic eosinophilic inflammation [13]. Studies of OPN express