Rat model of chronic tympanic membrane perforation: Ventilation tube with mitomycin C and dexamethasone

Objective: Chronic tympanic membrane perforation (TMP) in a clinical setting may attract surgical intervention. With the advent of modern biomaterials, new options are available for myringoplasty but safety and efficacy need evaluation in a chronic TMP animal model. The aim of this study was to evaluate the efficacy of ventilation tube (VT) insertion in conjunction with topical application of mitomycin Cl dexamethasone (M/D) for the creation of chronic TMP in rats. Methods: Thirty male Sprague-Dawley rats underwent myringotomy of the right tympanic membrane (TM) and were divided into three experimental groups: spontaneous healing (myringotomy control), VT insertion for 2 weeks and VT insertion for 2 weeks in conjunction with topical application of M/D (VT-M/D). All TMs were regularly assessed by otoscopy for 10 weeks and then animals were sacrificed for histological evaluation. Results: In the VT-M/D group, seven out of ten (70%) perforations were patent at 10 weeks (mean patency, 57.9 days; P < 0.01). The VT group had two out of ten (20%) perforations patent at 10 weeks (mean patency, 26.5 days; P < 0.01), while all TMPs from the myringotomy control group were closed by day 9 (mean patency, 7.2 days). Histologically, the TMPs patent at week 10 had a stratified squamous epithelialized rim, keratinocyte layer thickening around the perforation edge as well as increased collagen deposition and macrophage infiltration. Conclusion: Chronic TMP in a rat model was successfully created by VT insertion and the efficacy was increased in combination with topical application of M/D. (C) 2015 Elsevier Ireland Ltd. All rights reserved.