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Diss. (sammanfattning) Uppsala : Univ., 2002. / Härtill 5 uppsatser.

<p>Topical treatment of several inner ear diseases through the round window membrane (RWM) might be feasible in the near future. Bacteria toxins, ototoxic drugs and noise trauma seem to harm the inner ear by a common pathway which involves, excessive outflow of the afferent neurotransmitter glutamate and formation of nitric oxide (NO), which can severely damage cells/nerve endings and lead to cell death.</p><p>In this study we used 98 Sprague-Dawley rats and seven human temporal bones. Various substances were instilled into the middle ear of the rat, such as Pseudomonas Aeruginosa Exotoxin (PaExoA), gentamicin, NO-inhibitor N-Omega-Nitro-L-Arginine Methyl Ester (L-NAME), and glucocorticoids. The effects of the substances were studied by morphological analysis of RWM and the endolymphatic sac (ES) by light and electron microscopic. Hearing level was measured in the rats by ABR technique. The human temporal bones were studied immunomorphologically to search for glutamate.</p><p>In the human inner ear, glutamate receptors and glutamine synthetase, were identified. In the rat, we found, following PaExoA exposure, reversible and permanent hearing loss and morphological changes in the RWM. The ES showed increased numbers of macrophages and thickening of the epithelia. When L-NAME was used as an otoprotector from gentamicin ototoxicity a therapeutic effect in the high frequency area was found. Hydrocortisone (but not dexamethasone) exposure of the RWM resulted in membrane thickening, and adjacent to the membrane, inflammatory cells.</p><p>The importance of the RWM as a portal for toxic substances and topical treatment of inner ear diseases was highlighted in this study. The difficulties of applying drugs in the round window niche were exposed. The results of this study add important knowledge concerning certain mechanisms of inner ear injury and help us to understand possibilities and problems of local treatment of inner ear diseases in patients.</p>

Topical treatment of several inner ear diseases through the round window membrane (RWM) might be feasible in the near future. Bacteria toxins, ototoxic drugs and noise trauma seem to harm the inner ear by a common pathway which involves, excessive outflow of the afferent neurotransmitter glutamate and formation of nitric oxide (NO), which can severely damage cells/nerve endings and lead to cell death. In this study we used 98 Sprague-Dawley rats and seven human temporal bones. Various substances were instilled into the middle ear of the rat, such as Pseudomonas Aeruginosa Exotoxin (PaExoA), gentamicin, NO-inhibitor N-Omega-Nitro-L-Arginine Methyl Ester (L-NAME), and glucocorticoids. The effects of the substances were studied by morphological analysis of RWM and the endolymphatic sac (ES) by light and electron microscopic. Hearing level was measured in the rats by ABR technique. The human temporal bones were studied immunomorphologically to search for glutamate. In the human inner ear, glutamate receptors and glutamine synthetase, were identified. In the rat, we found, following PaExoA exposure, reversible and permanent hearing loss and morphological changes in the RWM. The ES showed increased numbers of macrophages and thickening of the epithelia. When L-NAME was used as an otoprotector from gentamicin ototoxicity a therapeutic effect in the high frequency area was found. Hydrocortisone (but not dexamethasone) exposure of the RWM resulted in membrane thickening, and adjacent to the membrane, inflammatory cells. The importance of the RWM as a portal for toxic substances and topical treatment of inner ear diseases was highlighted in this study. The difficulties of applying drugs in the round window niche were exposed. The results of this study add important knowledge concerning certain mechanisms of inner ear injury and help us to understand possibilities and problems of local treatment of inner ear diseases in patients.

Objectifs: La pathophysiologie de la maladie de Ménière (MM) demeure mal comprise. Nous avons identifié dans la littérature un groupe de protéines exprimées sur le sac endolymphatique (SEL) et impliquées dans la régulation du volume endolymphatique : l’Aquaporine-2 (AQP2), le récepteur V2R de vasopressine (AVP), le Co-transporteur de Sodium Potassium et Chlorure type 2 (NKCC2) et le canal TRP type V4 (TRPV4). Notre objectif est de déterminer si leur expression sur le SEL est altérée dans la MM, pour améliorer notre compréhension de la physiologie de l’hydrops endolymphatique. Méthodes: Recrutement des cas de MM et schwannomes vestibulaires (SV) comme contrôles, le jour de leurs chirurgies respectives. Prélèvement de biopsies de SEL et sang pour AVP. L’immunohistochimie pour AQP2, V2R, NKCC2 et TRPV4 fut effectuée, et les lames scannées pour analyse digitale de densité d’expression par un logiciel spécialisé (VIS par Visiopharm®). Résultats: Total de 27 cas MM et 23 contrôles. Les scores générés par le logiciel représentent la densité d’expression totale et relative des protéines, exclusivement sur l’épithélium du SEL. Les scores d’AQP2 sont élevés de façon significative dans la MM comparée aux contrôles (p = 0.018). Nous ne rapportons aucune variation significative pour AVP, V2R, NKCC2 et TRPV4. Conclusion: Cette étude originale évalue l’expression simultanée de AQP2, V2R, NKCC2 et TRPV4 sur le SEL dans la MM, avec un groupe contrôle (SV). Nos résultats démontrent une augmentation isolée de l’AQP2 dans la MM. Nous proposons une surexpression constitutive de cette dernière, indépendante de son axe de régulation (AVP-V2R). Une mutation somatique au niveau des séquences régulatrices pourrait justifier nos observations. / Objectives: Endolymphatic sac (ELS) pathophysiology in Ménière’s Disease (MD) remains poorly understood. We identified from the literature a group of proteins expressed on the ELS and involved in endolymph volume regulation: Aquaporin-2 (AQP2), vasopressin receptor V2R, Sodium Potassium Chloride Cotransporter type 2 (NKCC2) and TRP channel type V4 (TRPV4). Our objective was to determine whether their ELS expression was altered in MD, to better understand the pathophysiology of endolymphatic hydrops. Methods: Patients with definite MD undergoing endolymphatic duct blockage surgery were recruited, as well as controls undergoing surgery for vestibular schwannomas (VS). ELS biopsies and blood samples for plasma Arginine Vasopressin (AVP) were obtained. Immunohistochemistry for AQP2, V2R, NKCC2 and TRPV4 was performed. Slides were scanned digitally for highly sensitive pixel density analysis by specialized software (VIS by Visiopharm®). Results: 27 definite MD patients and 23 VS controls were included. Global scores generated by the software represent total and relative protein expression density of 3 staining intensity levels, exclusively on ELS epithelium. AQP2 expression density was significantly elevated in MD compared to VS (p = 0.018). There was no significant difference in plasma AVP, V2R, NKCC2 and TRPV4 expression. Conclusion: This original study evaluates simultaneous in-situ expression of AQP2, V2R, NKCC2 and TRPV4 on the human ELS in MD, with a VS control group. Our results show only AQP2 up regulation on the ELS of MD patients. We suggest a constitutively increased expression of AQP2 in MD, independent of its regulatory axis (AVP-V2R). Acquired regulator sequence mutations could support this model.