Morphological changes in the round window membrane associated with Haemophilus influenzae-induced acute otitis media in the chinchilla |
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| Institution: | 1. School of Aerospace and Mechanical Engineering and Biomedical Engineering Center, University of Oklahoma, Norman, OK, USA;2. Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA;1. Instituto de Fisiología, Facultad de Ciencias Médicas, Universidad Nacional de Córdoba (UNC), Santa Rosa 1085, X5000ESU, Córdoba, Argentina;2. Instituto de Investigaciones en Ciencias de la Salud (INICSA), CONICET and UNC. Santa Rosa 1085, X5000ESU, Córdoba, Argentina;3. Instituto de Ciencia y Tecnología de Alimentos, Edificio de Investigaciones Biológicas y Tecnológicas, Av. Velez Sarsfield 1611,- Facultad de Ciencias Exactas, Físicas y Naturales (FCEFyN), UNC/CONICET, Córdoba X5016GCA, Argentina;1. School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK, USA;2. Dept. of Mechanical Engineering, University of Texas at Dallas, Richardson, TX, USA;3. Dept. of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA;1. Department of Otolaryngology-Head and Neck Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan;2. Department of Medical Bioinformatics, Hokkaido Information University, 59-2 Nishi Nopporo, Ebetsu, Hokkaido 069-8585, Japan;1. Department of Mechanical Engineering, The University of Texas at Dallas, Richardson, TX, 75080, USA;2. School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK, 73019, USA |
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| Abstract: | ObjectiveThe round window membrane (RWM) encloses the round window, the opening into the scala tympani (ST) from the middle ear. During the course of acute otitis media (AOM), structural changes of the RWM can occur that potentially affect sound transmission into and out of the cochlea. The relationship between such structural changes and conductive hearing loss during AOM has remained unclear. The focus of the current study was to compare the thickness distribution across the RWM surface between normal ears and those with AOM in the chinchilla. We assessed the occurrence of AOM-associated histological changes in this membrane compared to uninfected control animals after AOM of two relatively short durations.Material and methodsAOM was induced by transbullar injection of the nontypeable Haemophilus influenzae strain 86-028NP into two groups of adult chinchillas (n = 3 each). Bullae were obtained from the two infected groups, at 4 days or 8 days post challenge. Structures and thickness of these RWMs were compared between the two infected treatment groups and to RWMs from uninfected control animals (n = 3) at seven different RWM locations.ResultsRWM thickness in infected chinchillas increased significantly at locations along the central line on the 4th day post bacterial challenge compared to values found for uninfected control animals. Lymphocyte infiltration and edema were the primary contributors to these thickness increases. No significant further increases in RWM thickness were observed when RWMs from chinchillas ears infected for 4 and 8 days were compared. Thickness and structural changes at the RWM lateral and medial areas were less visually obvious and not statistically significant among the three treatment groups. These latter RWM regions clearly were less affected during AOM than the central areas.ConclusionsThis histological study establishes that H. influenzae-induced AOM causes significant acute changes in chinchilla RWM structure that are characterized by region-specific increases in thickness. Our new morphological findings comparing normal and diseased chinchilla RWMs identify yet another biomechanical mechanism by which nontypeable H. influenzae may contribute to hearing loss in AOM. |
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| Keywords: | Acute otitis media Round window membrane Histology Chinchilla |
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