Structural changes in the rat middle ear mucosa due to endotoxin and eustachian tube obstruction

• Published in: European archives of oto-rhino-laryngology Vol. 256; no. 4; pp. 167 - 172
• Main Authors: NELL, M. J, GROTE, J. J
• Format: Journal Article
• Language: English
• Published: Berlin Springer 1999
• Subjects: Animals; Biological and medical sciences; Ear, auditive nerve, cochleovestibular tract, facial nerve: diseases, semeiology; Endotoxins - pharmacology; Endotoxins - physiology; Epithelial Cells - ultrastructure; Eustachian Tube - pathology; Female; Haemophilus influenzae; Medical sciences; Mucous Membrane - pathology; Mucous Membrane - ultrastructure; Non tumoral diseases; Otitis Media with Effusion - pathology; Otorhinolaryngology. Stomatology; Rats; Rats, Wistar; Salmonella typhimurium; Effusion; Rat; Pathogenesis; Middle ear disease; Mucosa; Rodentia; Experimental study; Endotoxin; Obstruction; Vertebrata; Mammalia; Ultrastructure; Animal; ENT disease; Otitis media; Biological effect; Middle ear; Eustachian tube
• ISSN: 0937-4477; 1434-4726
• DOI: 10.1007/s004050050134

The middle ears of 48 rats were used to examine the effects of endotoxin injection, eustachian tube obstruction or a combination of eustachian tube obstruction and endotoxin injection. Animals were killed after 1, 2, 4, or 12 weeks and the middle ears processed for light and scanning electron microscopy. Compared to the normal middle ear mucosa, the epithelial layer was more pseudostratified, cuboidal or cylindrical after endotoxin injection or obstruction of the eustachian tube. In the early phase, numerous ciliated cells occurred in areas originally almost devoid of these cells. At 3 months, degeneration of ciliated cells was observed. The combination of eustachian tube obstruction and endotoxin injection also induced a more pseudostratified, cuboidal or cylindrical epithelium with an increased number of goblet cells. However, an early decrease occurred in the number of ciliated cells in the tympanic orifice of the eustachian tube. Furthermore, inflammatory cells, mainly PMNs, macrophages and lymphocytes, invaded the subepithelial layer after eustachian tube obstruction and endotoxin injection. These structural changes resulted in an impairment of the mucociliary transport system for clearance of the middle ear cavity. For this reason we believe that both endotoxin and eustachian tube obstruction or dysfunction play an important role in inducing persistent mucosal changes in the middle ear cavity, thereby prolonging otitis media with effusion.