Abstract
HypothesisThe middle ear contains homeostatic mechanisms that control the movement of ions and fluids similar to those present in the inner ear, and are altered during inflammation.BackgroundThe normal middle ear cavity is fluid-free and air-filled to allow for effective sound transmission. Within the inner ear, the regulation of fluid and ion movement is essential for normal auditory and vestibular function. The same ion and fluid channels active in the inner ear may have similar roles with fluid regulation in the middle ear.MethodsMiddle and inner ears from BALB/c mice were processed for immunohistochemistry of 10 specific ion homeostasis factors to determine if similar transport and barrier mechanisms are present in the tympanic cavity. Examination also was made of BALB/c mice middle ears after transtympanic injection with heat-killed Haemophilus influenza to determine if these channels are impacted by inflammation.ResultsThe most prominent ion channels in the middle ear included aquaporins 1, 4 and 5, claudin 3, ENaC and Na+,K+-ATPase. Moderate staining was found for GJB2, KCNJ10 and KCNQ1. The inflamed middle ear epithelium showed increased staining due to expected cellular hypertrophy. Localization of ion channels was preserved within the inflamed middle ear epithelium.ConclusionsThe middle ear epithelium is a dynamic environment with intrinsic mechanisms for the control of ion and water transport to keep the middle ear clear of fluids. Compromise of these processes during middle ear disease may underlie the accumulation of effusions and suggests they may be a therapeutic target for effusion control.
Highlights
Otitis media is a common disorder affecting approximately 90% of children and is the leading cause of conductive hearing loss in children worldwide. [1] A fluid-free and air-filled middle ear cavity is required for effective sound transmission
Middle and inner ears from BALB/c mice were processed for immunohistochemistry of 10 specific ion homeostasis factors to determine if similar transport and barrier mechanisms are present in the tympanic cavity
The middle ear epithelium is a dynamic environment with intrinsic mechanisms for the control of ion and water transport to keep the middle ear clear of fluids
Summary
Otitis media is a common disorder affecting approximately 90% of children and is the leading cause of conductive hearing loss in children worldwide. [1] A fluid-free and air-filled middle ear cavity is required for effective sound transmission. [1] A fluid-free and air-filled middle ear cavity is required for effective sound transmission. Middle ear effusion is a component of acute otitis media. Transepithelial ion and water transport for endolymph homeostasis in the inner ear tightly controls the endolymphatic potential required for normal auditory and vestibular function. [3,12,13,14] a thorough evaluation of such ion and water transport channels in the middle ear has not been conducted. The present study employed immunohistochemistry to identify the expression and localization of ion channels, water channels, and junctional proteins in the normal murine middle ear epithelium to determine if they are potentially involved in fluid regulation. The normal middle ear cavity is fluid-free and air-filled to allow for effective sound transmission. The same ion and fluid channels active in the inner ear may have similar roles with fluid regulation in the middle ear
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