Validation of a Mouse Model of Dysfunctional Oropharyngeal Swallowing-Induced Aspiration Pneumonia

To validate a mouse nerve injury model of microaspiration pneumonia due to dysfunctional oropharyngeal swallowing.

C57BL/6J mice were divided into nerve transection (Nx; in which the left hypoglossal and vagus nerves were transected) and nonsurgical control groups. The lungs were removed the day after nerve transection. Then, the expression of inflammation-related genes (TNFα, CCL2, and IL-6) in the lung tissue was measured via qPCR and lung tissues were evaluated histologically via HE staining (Ctl = 6, Nx = 4). Bronchoalveolar lavage fluid (BALF) was collected at these time points, and neutrophils were analyzed via FACS (Ctl = 6, Nx = 5). Other mice were given water mixed with Tc-99m, and 18 h after surgery, BALF and stomach fluid were collected, and the Tc-99m radioactive count in each sample was measured via gamma counter (Ctl = 9, Nx = 10).

Compared to controls, the expression of the CCL2 gene in lung tissue, the number of neutrophils in BALF, and the ratio of gamma counts in BALF/stomach fluid, which represents the actual Tc-99m radioactive count in BALF, were significantly higher (p < 0.05) in the Nx group. Inflammatory cell infiltration of the lung was seen histologically in the Nx group, suggesting the existence of microaspiration.

Microaspiration pneumonia due to oropharyngeal dysphagia was detected following unilateral hypoglossal and vagus nerve transection in mice, suggesting validation of the oropharyngeal microaspiration mouse model with nerve transection.

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