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FP Paulsen, AP Corfield, M Gebhardt, P Steven, U Schaudig, AB Thale, M Berry; Distribution of Mucins in Human Nasolacrimal Ducts . Invest. Ophthalmol. Vis. Sci. 2002;43(13):899.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To assess the expression and production of mucins in the epithelium of human efferent lacrimal ducts. Mucins are important structural and functional components of the precorneal tear film and the nasal mucosa. Methods: Expression of mucins was monitored by reverse transcription-polymerase chain reaction analysis. Immunohistochemistry using antibodies specific for the polypeptide core of mucins was performed to determine the presence and distribution of mucins in the epithelia of the lacrimal passage. Results: mRNA expression for MUC1, MUC2, MUC4, MUC5AC, MUC5B, and MUC7, but not MUC6, was detected in human nasolacrimal ducts. Immunohistochemistry revealed MUC5AC and in some cases MUC1 associated with goblet and mucous cells of subepithelial seromucous glands. MUC2 was only detected in scattered cell conglomerates where it was visible in both epithelial and goblet cells. MUC4 could not be detected by immunostaining using antibody 4F12. MUC5B was mainly visible in epithelial cells but also in many goblet cells. MUC7 occurred in epithelial cells of the lacrimal sac and the nasolacrimal duct as well as in acinar cells of subepithelial seromucous glands but seemed to be absent in goblet cells. Conclusions: Human efferent tear ducts produce a broad spectrum of mucins. This mucin pattern is comparable with human conjunctiva (MUC1, MUC2, MUC4 and MUC5AC)and salivary glands (MUC5B and MUC7). The localization of MUC5B and MUC7 is remarkably similar to that of the trefoil factor peptide 3 (TFF3) which might aggregate with either mucin. Moreover, MUC 7 interacts with a variety of oral microorganisms and may support microbial defense in the lacrimal passage. The production of a broad spectrum of mucins inside the nasolacrimal ducts suggests a special role in tear fluid transport through the lacrimal passage. Further investigations of mucins and trefoil peptides expression in the tear drainage system are needed in order to fully understand the physiological function of mucins in the nasolacrimal ducts.
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