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. 2022 Sep-Oct;88(5):701-707.
doi: 10.1016/j.bjorl.2020.09.011. Epub 2020 Oct 28.

Morphological and pathological changes of Eustachian tube mucosa in an animal model of eosinophilic otitis media

Jinsong Yang  1 , Chunli Zhao  1 , Peiwei Chen  1 , Shouqin Zhao  2
Affiliations

Morphological and pathological changes of Eustachian tube mucosa in an animal model of eosinophilic otitis media

Jinsong Yang et al. Braz J Otorhinolaryngol. 2022 Sep-Oct.

Abstract

Introduction: Eosinophilic otitis media is an intractable otitis media and a fairly common middle ear disease. However, the pathogenesis of eosinophilic otitis media is obscure.

Objective: To observe the pathological and ultrastructural changes of the Eustachian tube mucosal epithelium in rats with eosinophilic otitis media and further explore the pathogenesis of eosinophilic otitis media.

Methods: Animals were intraperitoneally injected with 2000 mg ovalbumin and 100 mg aluminum hydroxide (alum) on day 0, followed by 100 mg ovalbumin and 100 mg alum injection on days 7 and 14. Next they were topically boosted by daily application of 100 mg ovalbumin solution via nasal drip and intratympanic injection of 0.1 mL ovalbumin (1000 mg/mL) in the right ear (group A, n = 80) and 0.1 mL saline in the left ear as control (group B, n = 80) starting on day 21 and continuing for 14 days. The temporal bones were dissected on the 35th, 38th, 41st and 43rd day separately under anesthesia. Scanning electron microscopy, hematoxylin-eosin and toluidine blue staining were used to observe the pathological and morphological changes of Eustachian tube mucosa stained samples. Moreover, inflammatory cells and cilia were counted.

Results: The epithelium of the Eustachian tube in group A was swollen and thickened. The cilia were arranged in a disorderly manner and partially detached. Eosinophils infiltrated the submucosal layer of the Eustachian tube, and their number increased significantly compared with that in group B (p < 0.05). Simultaneously, mast cell degranulation was observed in group A. Scanning electron microscopy revealed that the cilia were lodged and gathered along the whole length of Eustachian tube in group A. Ciliated cell density was significantly lower than that in Group B (p < 0.01).

Conclusion: In the eosinophilic otitis media model, allergy caused significant changes in pathology and morphology of the Eustachian tube mucosa, affecting the normal function of the Eustachian tube which played an important role in the occurrence and development of eosinophilic otitis media.

Keywords: Allergy; Cilia; Eosinophilic otitis media; Eustachian tube; Mucosa.

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Figures

Figure 1
Figure 1
(A) ET from group A presents with ciliated epithelial cell swelling, disordered and shedding cilia, thickened mucosa, and enlarged and expanded capillaries. (B) ET mucosal epithelium from group B revealed slightly swollen ciliated epithelium, with normal and neatly arranged cilia structure.
Figure 2
Figure 2
(A) The view of eosinophils and neutrophils in group A. (B) The view of eosinophils and neutrophils in group B (HE ×l000).
Figure 3
Figure 3
(A) Infiltration of mast cells in the tissue around the ET in group A. The black arrow indicates mast cells. The asterisk (*) corresponds to ET lumen (toluidine blue staining ×400). (B) Degranulation of active mast cells in the tissue around the ET in group A. Black arrow points to activated mast cells (toluidine blue stain ×1000).
Figure 4
Figure 4
(A) The counts of the eosinophils in group A were significantly higher than these in group B, and the difference was statistically significant (p < 0.05). (B) The number of mast cells in group A was significantly higher than that in group B, and the difference was statistically significant (p < 0.05). (C) The counts of the neutrophils did not differ significantly between the two groups.
Figure 5
Figure 5
(A and B) Morphological structure of the ET mucosa in group A under SEM. There is a significant and discontinuous loss of cilia in the ET mucosa. The number of ciliated cells in the opening area near the tympanic cavity is significantly reduced and the density decreased. In (A), the black arrow is directed toward the cilia missing area. In (B), the black arrow points to cilia obviously lodged, and a gathering area on a massive scale. (C and D) Morphological structure of the ET mucosa in group B under SEM. In (C), the full-length surface of the ET mucosa is covered with cilia, without ciliary loss or obvious lodging. In (D), the ciliated cells are scattered in the middle of the mucosa; The “G” indicates goblet cells.
Figure 6
Figure 6
The number of ciliated cells in group A was significantly lower than that in group B. The difference was statistically significant (p < 0.05).
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