Hypothesis: A rat model for patulous Eustachian tube (PET) can be used to assess the therapeutic efficacy of different injection materials for Eustachian tube (ET) mucosal injection. Background: A small animal model is required to determine the optimal injection material for PET treatment. We aimed to develop an experimental rat model to investigate a suitable injection material for ET mucosal injection. Methods: After developing a submucosal injection technique in 12-week-old male Crl:CD Sprague-Dawley rats, the optimal injection volume was determined using cadaver rats by injecting saline into the ET mucosa. In live rats, we injected saline or atelocollagen under the ET mucosa and analyzed the passive opening pressure (POP) changes over time. Histologic evaluation was performed after atelocollagen injection. Changes in the POP after atelocollagen injection were also examined using a rat model of PET created by transecting the mandibular nerve. Results: The optimal injection volume was determined to be 20 µL. The increase in the POP was observed from immediately after injection to 4 days post-injection with saline and from immediately after injection to 7 days post-injection with atelocollagen. Histopathologic evaluation showed that atelocollagen remained in the submucosal layer of the ET even 28 days after injection. In the PET rat model, the POP increased immediately after injection and remained stable for 7 days, reaching levels equivalent to those before mandibular nerve transection. Conclusions: This model has the potential to be widely used as a test system for investigating the efficacy and safety of suitable substances for ET mucosal injection in PET treatment.
Koike et al. (Thu,) studied this question.