Effects of acid solutions at different concentrations on ciliary cells in eustachian tube mucosa of rats

The pharyngeal orifice of the Eustachian tube is located in the nasopharynx. Gastroesophageal reflux of gastric juice into the upper airway can cause damage to the Eustachian tube mucosa, which subsequently leads to secretory otitis media. However, the mechanism underlying Eustachian tube mucosal injury remains unclear. We hypothesize that gastric acid impairs the ciliary beating of the epithelial cells in the Eustachian tube mucosa, thereby compromising the mucociliary clearance function of the epithelium. In this study, the Eustachian tube mucosal epithelium of rats was incubated in phosphate-buffered saline (PBS) and hydrochloric acid solutions of varying concentrations. The samples were observed under a high-speed video microscope to evaluate the mucosal epithelial morphology and ciliary beating frequency. After incubation, the mucosal tissues were harvested, stained, and examined under a fluorescence microscope to measure the ciliary density of the mucosal epithelium. The following observations were obtained: Acid solutions did not induce significant ciliary detachment from the Eustachian tube mucosal epithelium, but they did cause a decrease in ciliary beating frequency. The lower the pH value of the solution, the more pronounced the inhibitory effect on ciliary beating frequency. These findings suggest that refluxate with an even lower pH may exert more severe damage to Eustachian tube mucosal function, thereby contributing to the development of related diseases.