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

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.

## 摘要
嗜酸性中耳炎（eosinophilic otitis media）是一种难治性中耳炎，亦是较为常见的中耳疾病。目前该病的发病机制尚不明确。
## 研究目的
观察嗜酸性中耳炎模型大鼠咽鼓管（Eustachian tube）黏膜上皮的病理及超微结构变化，进一步探究嗜酸性中耳炎的发病机制。
## 实验方法
于第0日对实验动物腹腔注射2000 mg卵清蛋白与100 mg氢氧化铝（铝佐剂），并于第7日、第14日再次注射100 mg卵清蛋白与100 mg铝佐剂。自第21日起，每日经鼻腔滴注100 mg卵清蛋白溶液进行局部致敏，并分别于右侧耳鼓室内注射0.1 mL浓度为1000 mg/mL的卵清蛋白（设为A组，n=80），左侧耳注射0.1 mL生理盐水作为对照（设为B组，n=80），持续14日。分别于第35、38、41、43日在麻醉状态下解剖获取颞骨。采用扫描电子显微镜、苏木精-伊红染色及甲苯胺蓝染色观察咽鼓管黏膜的病理及形态学变化，并对炎性细胞与纤毛进行计数。
## 实验结果
A组大鼠咽鼓管上皮肿胀增厚，纤毛排列紊乱且部分脱落；嗜酸性粒细胞浸润至咽鼓管黏膜下层，其数量较B组显著升高（P<0.05）。同时，A组可见肥大细胞脱颗粒现象。扫描电子显微镜观察显示，A组大鼠咽鼓管全长的纤毛均出现倒伏、聚集情况，纤毛细胞密度显著低于B组（P<0.01）。
## 研究结论
在嗜酸性中耳炎模型中，变应原致敏可显著改变咽鼓管黏膜的病理与形态学特征，影响咽鼓管正常功能，该变化在嗜酸性中耳炎的发生发展过程中发挥了重要作用。