Aquaporin expression in the lacrimal sac of patients with primary and functional nasolacrimal duct obstruction

Purpose To compare the expression profile of aquaporins (AQPs), a family of membrane proteins that function as selective pores in the epithelium of the lacrimal sac in patients with primary or functional nasolacrimal duct obstruction. Methods Forty lacrimal sacs were obtained from 20 patients with primary nasolacrimal duct obstruction (group 1) and 20 patients with functional nasolacrimal duct obstruction (group 2) during endoscopic endonasal dacryocystorhinostomy. Western blot and immunohistochemical analyses were performed to determine the presence and distribution of AQPs in the epithelium and subepithelial glands of the nasolacrimal ducts. Results AQP 1, 2, 3, 4 and 5 were identified by western blot analysis. Quantified AQP levels were higher in group 2 than in group 1, although this was not statistically significant (p=0.857 for AQP 1, p=0.370 for AQP 2, p=0.813 for AQP 3, p=0.766 for AQP 4 and p=0.429 for AQP 5 by Mann-Whitney U test). Immunohistochemical analyses revealed AQPs 1, 3, 5, 7 and 10. Expression of AQP 1, 3, 5, 7 and 10 was statistically significantly greater in group 2 than in group 1 (p=0.022 for AQP 1, p=0.028 for AQP 3, p=0.002 for AQP 5, p=0.041 for AQP 7 and p=0.001 for AQP 10 by Mann-Whitney U test). Conclusions AQP expression in functional nasolacrimal duct obstruction had a tendency towards being higher than in primary nasolacrimal duct obstruction, although this was only statistically significant on immunohistochemistry.