Expression of glycoconjugates in human eustachian tubes with otitis media

Objectives: To characterize glycoconjugate expression in normal human eustachian tubes and study the alterations in glycoconjugate expression found in eustachian tubes with otitis media. Study Design: Using lectin histochemistry, alterations in glycoconjugates were studied in three normal temporal bones, in four temporal bones with mucoid otitis media (MOM), and in five with serous otitis media (SOM). Methods: Sections of previously processed temporal bones were decelloidinized, and then incubated with seven biotinylated lectins - WGA, SNA, MAA, BPA, PNA, UEA-1, and LcH - that reflect seven carbohydrate residues of glycoconjugates, respectively: GlcNAc/NeuNAc, NeuNAcα(2-6)GalNAc, NeuNAcα(2-3)GalNAc, Galβ(1-3) GalNAc, L-fucose, and α-mannose residues. Control sections were incubated with inhibitory carbohydrates or without biotinylated lectins. Results: In the normal temporal bones, five carbohydrate residues in goblet cells and cilia of the eustachian tube demonstrated moderate to strong activity - NeuNAcα(2- 6)GalNAc, NeuNAcα(2-3)GalNAc, GalNAc, Galβ(1-3)GalNAc, and L-fucose. Two residues demonstrated weak activity-GlcNAc/NeuNAc and α-mannose. Temporal bones with MOM revealed increases in sialic acid and α-mannose, and a decrease in L-fucose. Residues of carbohydrates in the cilia of bones with SOM were notably decreased, especially for GalNAc, Galβ(1-3)GalNAc, and NeuNAcα(2-6)GalNAc. Conclusions: Glycoconjugates in the normal human eustachian tube are rich in GalNAc, Galβ(1-3)GalNAc, L-fucose, and NeuNAcα(2-3/2-6) GalNAc, but low in α-mannose and sialic acid. Eustachian tubes from cases with SOM or MOM demonstrated alterations in glycoconjugate expression in cilia and goblet cells, which may reflect disorder of the carbohydrate metabolism during otitis media, especially in SOM.