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Mom R, Réty S, Mocquet V, Auguin D. In silico pharmacological study of AQP2 inhibition by steroids contextualized to Ménière's disease treatments. Front Neurol 2023; 14:1270092. [PMID: 37928160 PMCID: PMC10620702 DOI: 10.3389/fneur.2023.1270092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 09/21/2023] [Indexed: 11/07/2023] Open
Abstract
Ménière's disease (MD) is characterized by an abnormal dilatation of the endolymphatic compartment called endolymphatic hydrops and is associated with fluctuating hearing losses and vertigo. Corticosteroid treatment is typically administered for its anti-inflammatory effects to MD patients. However, we recently described for the first time a direct interaction of two corticosteroids (dexamethasone and cortisol) with human AQP2 which strongly inhibited water fluxes. From these initial studies, we proposed an AQPs Corticosteroids Binding Site (ACBS). In the present work, we tested the interaction of 10 molecules associated to the steroid family for this putative ACBS. We observed a wide diversity of affinity and inhibitory potential of these molecules toward AQP2 and discussed the implications for inner ear physiology. Among the tested compounds, cholecalciferol, calcitriol and oestradiol were the most efficient AQP2 water permeability inhibitors.
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Affiliation(s)
- Robin Mom
- Laboratoire de Biologie et Modélisation de la Cellule, École Normale Supérieure de Lyon, CNRS, UMR 5239, INSERM U1293, Université Claude Bernard Lyon 1, Lyon, France
- Research Group on Vestibular Pathophysiology, CNRS, Unit GDR2074, Marseille, France
| | - Stéphane Réty
- Laboratoire de Biologie et Modélisation de la Cellule, École Normale Supérieure de Lyon, CNRS, UMR 5239, INSERM U1293, Université Claude Bernard Lyon 1, Lyon, France
| | - Vincent Mocquet
- Laboratoire de Biologie et Modélisation de la Cellule, École Normale Supérieure de Lyon, CNRS, UMR 5239, INSERM U1293, Université Claude Bernard Lyon 1, Lyon, France
| | - Daniel Auguin
- Laboratoire de Physiologie, Ecologie et Environnement (P2E), UPRES EA 1207/USC INRAE-1328, UFR Sciences et Techniques, Université d’Orléans, Orléans, France
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Li H, Rajan GP, Shaw J, Rohani SA, Ladak HM, Agrawal S, Rask-Andersen H. A Synchrotron and Micro-CT Study of the Human Endolymphatic Duct System: Is Meniere's Disease Caused by an Acute Endolymph Backflow? Front Surg 2021; 8:662530. [PMID: 34136526 PMCID: PMC8200827 DOI: 10.3389/fsurg.2021.662530] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 04/19/2021] [Indexed: 11/13/2022] Open
Abstract
Background: The etiology of Meniere's disease (MD) and endolymphatic hydrops believed to underlie its symptoms remain unknown. One reason may be the exceptional complexity of the human inner ear, its vulnerability, and surrounding hard bone. The vestibular organ contains an endolymphatic duct system (EDS) bridging the different fluid reservoirs. It may be essential for monitoring hydraulic equilibrium, and a dysregulation may result in distension of the fluid spaces or endolymphatic hydrops. Material and Methods: We studied the EDS using high-resolution synchrotron phase contrast non-invasive imaging (SR-PCI), and micro-computed tomography (micro-CT). Ten fresh human temporal bones underwent SR-PCI. One bone underwent micro-CT after fixation and staining with Lugol's iodine solution (I2KI) to increase tissue resolution. Data were processed using volume-rendering software to create 3D reconstructions allowing orthogonal sectioning, cropping, and tissue segmentation. Results: Combined imaging techniques with segmentation and tissue modeling demonstrated the 3D anatomy of the human saccule, utricle, endolymphatic duct, and sac together with connecting pathways. The utricular duct (UD) and utriculo-endolymphatic valve (UEV or Bast's valve) were demonstrated three-dimensionally for the first time. The reunion duct was displayed with micro-CT. It may serve as a safety valve to maintain cochlear endolymph homeostasis under certain conditions. Discussion: The thin reunion duct seems to play a minor role in the exchange of endolymph between the cochlea and vestibule under normal conditions. The saccule wall appears highly flexible, which may explain occult hydrops occasionally preceding symptoms in MD on magnetic resonance imaging (MRI). The design of the UEV and connecting ducts suggests that there is a reciprocal exchange of fluid among the utricle, semicircular canals, and the EDS. Based on the anatomic framework and previous experimental data, we speculate that precipitous vestibular symptoms in MD arise from a sudden increase in endolymph pressure caused by an uncontrolled endolymphatic sac secretion. A rapid rise in UD pressure, mediated along the fairly wide UEV, may underlie the acute vertigo attack, refuting the rupture/K+-intoxication theory.
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Affiliation(s)
- Hao Li
- Department of Surgical Sciences, Section of Otolaryngology and Head and Neck Surgery, Uppsala University Hospital, Uppsala, Sweden
| | - Gunesh P. Rajan
- Department of Otolaryngology, Head and Neck Surgery, Luzerner Kantonsspital, Lucerne, Switzerland
- Department of Otolaryngology, Head and Neck Surgery Division of Surgery, Medical School, University of Western Australia, Perth, WA, Australia
| | - Jeremy Shaw
- Centre for Microscopy, Characterisation and Analysis, Perth, WA, Australia
| | - Seyed Alireza Rohani
- Department of Otolaryngology-Head and Neck Surgery, Western University, London, ON, Canada
| | - Hanif M. Ladak
- Department of Medical Biophysics and Department of Electrical and Computer Engineering, Western University, London, ON, Canada
| | - Sumit Agrawal
- Department of Otolaryngology-Head and Neck Surgery, Western University, London, ON, Canada
| | - Helge Rask-Andersen
- Department of Surgical Sciences, Section of Otolaryngology and Head and Neck Surgery, Uppsala University Hospital, Uppsala, Sweden
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A Micro-CT and Synchrotron Imaging Study of the Human Endolymphatic Duct with Special Reference to Endolymph Outflow and Meniere's Disease. Sci Rep 2020; 10:8295. [PMID: 32427861 PMCID: PMC7237694 DOI: 10.1038/s41598-020-65110-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 04/27/2020] [Indexed: 12/22/2022] Open
Abstract
Meniere’s disease remains enigmatic, and has no treatment with sufficient evidence. The characteristic histopathological finding is endolymphatic hydrops, suggesting either an overproduction or decreased reabsorption of endolymph in the human inner ear. This study presents the first analysis of the vascular plexus around the human endolymphatic duct using micro computed tomography and coherent synchrotron radiation with phase contrast imaging. Using a software program, data were processed by volume-rendering with scalar opacity mapping to create transparent three-dimensional reconstructions. A rich vascular plexus was discovered around the endolymphatic duct that drained into collecting channels, linked to the vestibular venous outflow system. This network is believed to make up the principal route for endolymph outflow, and its associated malfunction may result in endolymphatic hydrops and Meniere’s disease.
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“Reversed polarization” of Na/K-ATPase—a sign of inverted transport in the human endolymphatic sac: a super-resolution structured illumination microscopy (SR-SIM) study. Cell Tissue Res 2019; 379:445-457. [DOI: 10.1007/s00441-019-03106-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 09/15/2019] [Indexed: 02/06/2023]
Abstract
AbstractThe human endolymphatic sac (ES) is believed to regulate inner ear fluid homeostasis and to be associated with Meniere’s disease (MD). We analyzed the ion transport protein sodium/potassium-ATPase (Na/K-ATPase) and its isoforms in the human ES using super-resolution structured illumination microscopy (SR-SIM). Human vestibular aqueducts were collected during trans-labyrinthine vestibular schwannoma surgery after obtaining ethical permission. Antibodies against various isoforms of Na/K-ATPase and additional solute-transporting proteins, believed to be essential for ion and fluid transport, were used for immunohistochemistry. A population of epithelial cells of the human ES strongly expressed Na/K-ATPase α1, β1, and β3 subunit isoforms in either the lateral/basolateral or apical plasma membrane domains. The β1 isoform was expressed in the lateral/basolateral plasma membranes in mostly large cylindrical cells, while β3 and α1 both were expressed with “reversed polarity” in the apical cell membrane in lower epithelial cells. The heterogeneous expression of Na/K-ATPase subunits substantiates earlier notions that the ES is a dynamic structure where epithelial cells show inverted epithelial transport. Dual absorption and secretion processes may regulate and maintain inner ear fluid homeostasis. These findings may shed new light on the etiology of endolymphatic hydrops and MD.
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Kim SH, Nam GS, Choi JY. Pathophysiologic Findings in the Human Endolymphatic Sac in Endolymphatic Hydrops: Functional and Molecular Evidence. Ann Otol Rhinol Laryngol 2019; 128:76S-83S. [PMID: 31092029 DOI: 10.1177/0003489419837993] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND The endolymphatic sac (ES) is a cystic structure situated on the posterior fossa dura and is connected to the luminal space of the vestibular organ through the endolymphatic duct, which branches into the utricular and saccular ducts. Unlike the cochlea and vestibule, the ES does not contain sensory epithelium in its luminal space, and a single layer of epithelial cells line the luminal surface area. The ES in the inner ear is thought to play a role in the regulation of inner ear homeostasis, fluid volume, and immune reaction. If these functions of the ES are disrupted, dysfunction of the inner ear may develop. The most well-known pathology arising from dysfunction of the ES is endolymphatic hydrops, characterized by an enlarged endolymphatic space due to the accumulation of excessive endolymphatic fluid. Although, molecular identities and functional evidence for the roles were identified in animal studies, basic studies of the human ES are relatively uncommon compared with those using animal tissues, because of limited opportunity to harvest the human ES. METHODS In this study, molecular and functional evidence for the role of the human ES in the development of endolymphatic hydrops are reviewed. RESULTS AND CONCLUSIONS Although evidence is insufficient, studies using the human ES have mostly produced findings similar to those of animal studies. This review may provide a basis for planning further studies to investigate the pathophysiology of disorders with the finding of endolymphatic hydrops.
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Affiliation(s)
- Sung Huhn Kim
- 1 Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, Republic of Korea.,2 The Airway Mucus Institute, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Gi-Sung Nam
- 1 Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Jae Young Choi
- 1 Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, Republic of Korea.,2 The Airway Mucus Institute, Yonsei University College of Medicine, Seoul, Republic of Korea
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Brown DJ, Sokolic L, Fung A, Pastras CJ. Response of the inner ear to lipopolysaccharide introduced directly into scala media. Hear Res 2018; 370:105-112. [PMID: 30366193 DOI: 10.1016/j.heares.2018.10.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 10/03/2018] [Accepted: 10/14/2018] [Indexed: 12/18/2022]
Abstract
In an attempt to develop an animal model of immune mediated Meniere's disease, we have injected lipopolysaccharide (LPS) directly into scala media of guinea pigs and monitored functional and morphological changes over a period of 6 weeks. Depending on the concentration of LPS, changes ranged from moderate-to-severe hearing loss and endolymphatic hydrops with minimal cellular infiltrate or fibrosis, to dense cellular infiltration that filled the scalae. Interestingly, higher concentrations of LPS not only induced severe cellular infiltration, hydrops, and hearing loss, but also a substantial enlargement of the endolymphatic duct and sac. Moreover, LPS injections into perilymph failed to induce hydrops, yet still resulted in cellular infiltration and fibrosis in the cochlea. This suggests that chronic hydrops resulting from an immune challenge of the cochlea may not be due to blockage of the endolymphatic duct and sac, restricting fluid absorption. Furthermore, injecting antigen into endolymph may produce chronic immune-mediated hydrops, and provide a more promising animal model of Meniere's, although animals did not display signs of vestibular dysfunction, and the hearing loss was relatively severe.
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Affiliation(s)
| | - Ljiljana Sokolic
- The University of Sydney, Meniere's Research Laboratory, Australia
| | - Albert Fung
- The University of Sydney, Meniere's Research Laboratory, Australia
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Honda K, Kim SH, Kelly MC, Burns JC, Constance L, Li X, Zhou F, Hoa M, Kelley MW, Wangemann P, Morell RJ, Griffith AJ. Molecular architecture underlying fluid absorption by the developing inner ear. eLife 2017; 6. [PMID: 28994389 PMCID: PMC5634787 DOI: 10.7554/elife.26851] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 09/10/2017] [Indexed: 12/26/2022] Open
Abstract
Mutations of SLC26A4 are a common cause of hearing loss associated with enlargement of the endolymphatic sac (EES). Slc26a4 expression in the developing mouse endolymphatic sac is required for acquisition of normal inner ear structure and function. Here, we show that the mouse endolymphatic sac absorbs fluid in an SLC26A4-dependent fashion. Fluid absorption was sensitive to ouabain and gadolinium but insensitive to benzamil, bafilomycin and S3226. Single-cell RNA-seq analysis of pre- and postnatal endolymphatic sacs demonstrates two types of differentiated cells. Early ribosome-rich cells (RRCs) have a transcriptomic signature suggesting expression and secretion of extracellular proteins, while mature RRCs express genes implicated in innate immunity. The transcriptomic signature of mitochondria-rich cells (MRCs) indicates that they mediate vectorial ion transport. We propose a molecular mechanism for resorption of NaCl by MRCs during development, and conclude that disruption of this mechanism is the root cause of hearing loss associated with EES.
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Affiliation(s)
- Keiji Honda
- Molecular Biology and Genetics Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, United States
| | - Sung Huhn Kim
- Anatomy and Physiology Department, Kansas State University, Manhattan, United States
| | - Michael C Kelly
- Developmental Neuroscience Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, United States
| | - Joseph C Burns
- Developmental Neuroscience Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, United States
| | - Laura Constance
- Anatomy and Physiology Department, Kansas State University, Manhattan, United States
| | - Xiangming Li
- Anatomy and Physiology Department, Kansas State University, Manhattan, United States
| | - Fei Zhou
- Anatomy and Physiology Department, Kansas State University, Manhattan, United States
| | - Michael Hoa
- Auditory Development and Restoration Program, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, United States
| | - Matthew W Kelley
- Developmental Neuroscience Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, United States
| | - Philine Wangemann
- Anatomy and Physiology Department, Kansas State University, Manhattan, United States
| | - Robert J Morell
- Genomics and Computational Biology Core, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, United States
| | - Andrew J Griffith
- Molecular Biology and Genetics Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, United States
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8
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Runggaldier D, Pradas LG, Neckel PH, Mack AF, Hirt B, Gleiser C. Claudin expression in the rat endolymphatic duct and sac - first insights into regulation of the paracellular barrier by vasopressin. Sci Rep 2017; 7:45482. [PMID: 28374851 PMCID: PMC5379655 DOI: 10.1038/srep45482] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 02/28/2017] [Indexed: 12/13/2022] Open
Abstract
Hearing and balance functions of the inner ear rely on the homeostasis of the endolymphatic fluid. When disturbed, pathologic endolymphatic hydrops evolves as observed in Menière’s disease. The molecular basis of inner ear fluid regulation across the endolymphatic epithelium is largely unknown. In this study we identified the specific expression of the tight junction (TJ) molecules Claudin 3, 4, 6, 7, 8, 10, and 16 in epithelial preparations of the rat inner ear endolymphatic duct (ED) and endolymphatic sac (ES) by high-throughput qPCR and immunofluorescence confocal microscopy. Further we showed that Claudin 4 in the ES is a target of arginine-vasopressin (AVP), a hormone elevated in Menière’s disease. Moreover, our transmission-electron microscopy (TEM) analysis revealed that the TJs of the ED were shallow and shorter compared to the TJ of the ES indicating facilitation of a paracellular fluid transport across the ED epithelium. The significant differences in the subcellular localization of the barrier-forming protein Claudin 3 between the ED and ES epithelium further support the TEM observations. Our results indicate a high relevance of Claudin 3 and Claudin 4 as important paracellular barrier molecules in the ED and ES epithelium with potential involvement in the pathophysiology of Menière’s disease.
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Affiliation(s)
- Daniel Runggaldier
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
| | - Lidia Garcia Pradas
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
| | - Peter H Neckel
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
| | - Andreas F Mack
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
| | - Bernhard Hirt
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
| | - Corinna Gleiser
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
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Kniep R. Otoconia: Mimicking a calcite-based functional material of the human body. From basic research to medical aspects. PURE APPL CHEM 2015. [DOI: 10.1515/pac-2015-0201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AbstractOtoconia (calcite-based biominerals) are part of the sensory system in the inner ear of vertebrates, acting as gravity receptors responding to linear accelerations. Biomimetic otoconia are grown by double-diffusion into gelatine-gel matrices, and represent the first example of successful imitation of a biomineral, not only in outer shape but also in composite structure and hierarchical inner architecture. Biomimetic and biogenic (human) otoconia are investigated by X-ray methods, chemical analytics, ESEM, and TEM. Shape development (morphogenesis) as well as (partial) dissolution of the calcite component of the composite underline the hierarchical inner architecture built of more dense rhombohedral branches (with plane end-faces) and a rounded, more porous belly area. Atomistic simulations are performed in order to get insight into very first nucleation steps. Based on the detailed observations made up to now, first assumptions for the function of otoconia are developed, including the questions of density distribution within the volume of the specimen, the surrounding endolymph, as well as anchoring and interconnections of otoconia. A final point concerns the degeneration of otoconia which is caused by complexing agents and/or changes in ion concentrations (and pH) of the endolymph.
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Affiliation(s)
- Rüdiger Kniep
- 1Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
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10
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Raft S, Andrade LR, Shao D, Akiyama H, Henkemeyer M, Wu DK. Ephrin-B2 governs morphogenesis of endolymphatic sac and duct epithelia in the mouse inner ear. Dev Biol 2014; 390:51-67. [PMID: 24583262 DOI: 10.1016/j.ydbio.2014.02.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 02/19/2014] [Indexed: 02/03/2023]
Abstract
Control over ionic composition and volume of the inner ear luminal fluid endolymph is essential for normal hearing and balance. Mice deficient in either the EphB2 receptor tyrosine kinase or the cognate transmembrane ligand ephrin-B2 (Efnb2) exhibit background strain-specific vestibular-behavioral dysfunction and signs of abnormal endolymph homeostasis. Using various loss-of-function mouse models, we found that Efnb2 is required for growth and morphogenesis of the embryonic endolymphatic epithelium, a precursor of the endolymphatic sac (ES) and duct (ED), which mediate endolymph homeostasis. Conditional inactivation of Efnb2 in early-stage embryonic ear tissues disrupted cell proliferation, cell survival, and epithelial folding at the origin of the endolymphatic epithelium. This correlated with apparent absence of an ED, mis-localization of ES ion transport cells relative to inner ear sensory organs, dysplasia of the endolymph fluid space, and abnormally formed otoconia (extracellular calcite-protein composites) at later stages of embryonic development. A comparison of Efnb2 and Notch signaling-deficient mutant phenotypes indicated that these two signaling systems have distinct and non-overlapping roles in ES/ED development. Homozygous deletion of the Efnb2 C-terminus caused abnormalities similar to those found in the conditional Efnb2 null homozygote. Analyses of fetal Efnb2 C-terminus deletion heterozygotes found mis-localized ES ion transport cells only in the genetic background exhibiting vestibular dysfunction. We propose that developmental dysplasias described here are a gene dose-sensitive cause of the vestibular dysfunction observed in EphB-Efnb2 signaling-deficient mice.
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Affiliation(s)
- Steven Raft
- Section on Sensory Cell Regeneration and Development, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Leonardo R Andrade
- Laboratory of Biomineralization, Institute of Biomedical Sciences, CCS, Universidade Federal do Rio de Janeiro, RJ 21941-902, Brazil
| | - Dongmei Shao
- Department of Otolaryngology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Haruhiko Akiyama
- Department of Orthopedics, Gifu University, Gifu City 501-1194, Japan
| | - Mark Henkemeyer
- Department of Developmental Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Doris K Wu
- Section on Sensory Cell Regeneration and Development, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA.
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Møller MN, Caye-Thomasen P, Qvortrup K. Oxygenated fixation demonstrates novel and improved ultrastructural features of the human endolymphatic sac. Laryngoscope 2013; 123:1967-75. [PMID: 23404212 DOI: 10.1002/lary.23929] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 09/26/2012] [Accepted: 11/12/2012] [Indexed: 11/12/2022]
Abstract
OBJECTIVES/HYPOTHESIS The purpose of the present study is to describe in detail the ultrastructure of the human endolymphatic sac using a new and improved method of fixation as well as a refined surgical approach in obtaining specimens. STUDY DESIGN Transmission electron microscopy of the human endolymphatic sac, employing an oxygenated fixative. METHODS Eighteen tissue samples of the human endolymphatic sac were obtained during surgery for vestibular schwannoma using the translabyrinthine approach. The specimens were fixed in 2% glutaraldehyde in an oxygenated fluorocarbon blood substitute vehicle before preparation by routine methods for transmission electron microscopy. We focused on the epithelial cell layer, subepithelial tissue, intraluminal content, and vascular tissue in both the intra- and extraosseous part of the endolymphatic sac. RESULTS We observed well-defined endolymphatic sac epithelial cell lining in all 18 specimens. In general, we found very well-preserved specimens with well-defined intracellular structures. In contrast to the results in former studies, a minimum of fixation artifacts was observed in the present study. Three different cell types were observed in the intraosseous part of the sac: mitochondria-rich cells, ribosome-rich cells, and nonclassifiable cells. A fourth cell type was found in the extraosseous part. Novel ultrastructural features of the epithelial lining and the subepithelial layer are described and discussed. CONCLUSIONS The results in the present study indicate an improvement in obtaining human tissue with optimal fixation for ultrastructural analysis and provide several novel morphologic observations. The potential functions of the endolymphatic sac are discussed with reference to former studies.
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Affiliation(s)
- Martin Nue Møller
- Department of Oto-Rhino-Laryngology, Head and Neck Surgery, University Hospital Rigshospitalet/Gentofte, Denmark.
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12
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Friis M, Thomsen AR, Poulsen SS, Qvortrup K. Experimental hyperactivity of the endolymphatic sac. Audiol Neurootol 2013; 18:125-33. [PMID: 23296206 DOI: 10.1159/000345977] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Accepted: 11/14/2012] [Indexed: 11/19/2022] Open
Abstract
Injury to the endolymphatic sac may play an important role in the pathogenesis of Ménière's disease, an inner ear disorder characterized by hearing loss, tinnitus and attacks of vertigo. Isoimmunization of 16 inbred Lewis rats with a crude endolymphatic sac extract and complete Freund's adjuvant induced hyperactivity of the endolymphatic sac. One group of rats was immunized by a single dose whereas a second group was immunized twice. Control animals were injected with Freund's adjuvant in saline only. Serum was collected from all rats by the end of the study and harvested autoantibodies were tested by immunohistochemistry. The endolymphatic sacs were investigated by transmission electron microscopy. Endolymphatic sac stimulation was observed in all immunized rats. Based on detailed ultrastructural observations, the degree of reactivity seemed proportional to the number of injections and the extent of immunization. Moreover, the ribosome-rich cells seemed hyperactive with an extravagant content of intracellular components: numerous rough endoplasmic reticulum and free ribosomes, morphological signs of extensive endo- and exocytosis, vesicles of material with a density similar to the homogeneous substance of which many were observed to fuse with primary lysozymes. Basolateral foldings were numerous and in the subepithelial capillaries formation of multiple and apposing fenestrations were observed. No endolymphatic sac stimulation was observed in the control animals. Specific ribosome-rich cell alterations identical to those present in the endolymphatic sac of Ménière's disease were observed 21 days after the first immunization. The observations suggest that either an autoantigen or a trophic factor, capable of inducing a hyperactivity of the ribosome-rich cells and an imbalance of the homogeneous substance metabolism, exists in the endolymphatic sac of the rat.
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Affiliation(s)
- Morten Friis
- Department of Otorhinolaryngology, Head & Neck Surgery and Audiology, Rigshospitalet, and Department of Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark.
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13
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Water channel proteins in the inner ear and their link to hearing impairment and deafness. Mol Aspects Med 2012; 33:612-37. [DOI: 10.1016/j.mam.2012.06.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 06/11/2012] [Accepted: 06/17/2012] [Indexed: 11/24/2022]
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Algin O, Berçin S, Akgunduz G, Turkbey B, Cetin H. Evaluation of labyrinthine fistula by MR cisternography. Emerg Radiol 2012; 19:557-60. [DOI: 10.1007/s10140-012-1050-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Accepted: 05/04/2012] [Indexed: 10/28/2022]
Affiliation(s)
- Oktay Algin
- Radiology Department, Ataturk Training and Research Hospital, Bilkent, Ankara, Turkey.
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15
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Objective Measurement of the Human Endolymphatic Sac Dimensions in Ménière's Disease. Otol Neurotol 2011; 32:1364-9. [DOI: 10.1097/mao.0b013e31822e967f] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Kim SH, Kim UK, Lee WS, Bok J, Song JW, Seong JK, Choi JY. Albumin-like protein is the major protein constituent of luminal fluid in the human endolymphatic sac. PLoS One 2011; 6:e21656. [PMID: 21738753 PMCID: PMC3126852 DOI: 10.1371/journal.pone.0021656] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2010] [Accepted: 06/07/2011] [Indexed: 11/29/2022] Open
Abstract
The endolymphatic sac (ES) is an inner ear organ that is connected to the cochleo-vestibular system through the endolymphatic duct. The luminal fluid of the ES contains a much higher concentration of proteins than any other compartment of the inner ear. This high protein concentration likely contributes to inner ear fluid volume regulation by creating an osmotic gradient between the ES lumen and the interstitial fluid. We characterized the protein profile of the ES luminal fluid of patients (n = 11) with enlarged vestibular aqueducts (EVA) by proteomics. In addition, we investigated differences in the protein profiles between patients with recent hearing deterioration and patients without hearing deterioration. The mean total protein concentration of the luminal fluid was 554.7±94.6 mg/dl. A total of 58 out of 517 spots detected by 2-DE were analyzed by MALDI-TOF MS. The protein profile of the luminal fluid was different from the profile of plasma. Proteins identified from 29 of the spots were also present in the MARC-filtered human plasma; however, the proteins identified from the other 25 spots were not detected in the MARC-filtered human plasma. The most abundant protein in the luminal fluid was albumin-like proteins, but most of them were not detected in MARC-filtered human plasma. The concentration of albumin-like proteins was higher in samples from patients without recent hearing deterioration than in patients with recent hearing deterioration. Consequently, the protein of ES luminal fluid is likely to be originated from both the plasma and the inner ear and considering that inner ear fluid volumes increase abnormally in patients with EVA following recent hearing deterioration, it is tempting to speculate that albumin-like proteins may be involved in the regulation of inner ear fluid volume through creation of an osmotic gradient during pathological conditions such as endolymphatic hydrops.
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Affiliation(s)
- Sung Huhn Kim
- Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, Korea
| | - Un-Kyoung Kim
- Department of Biology, Kyungpook National University, Daegu, Korea
| | - Won-Sang Lee
- Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, Korea
| | - Jinwoong Bok
- Department of Anatomy, Yonsei University College of Medicine, Seoul, Korea
| | - Jung-Whan Song
- Department of Otorhinolaryngology, Ajou University College of Medicine, Suwon, Korea
| | - Je Kyung Seong
- Laboratory of Developmental Biology and Genomics, BK21 Program for Veterinary Science, Research Institute for Veterinary Science, College of Veterinary Medicine, Interdisciplinary Program for Bioinformatics and Program for Cancer Biology, Seoul National University, Seoul, Korea
| | - Jae Young Choi
- Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, Korea
- * E-mail:
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The subcellular distribution of aquaporin 5 in the cochlea reveals a water shunt at the perilymph–endolymph barrier. Neuroscience 2010; 168:957-70. [DOI: 10.1016/j.neuroscience.2009.09.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2009] [Revised: 08/30/2009] [Accepted: 09/01/2009] [Indexed: 11/23/2022]
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Rask‐Andersen H, Kinnefors A, Svedberg M, Illing R. The human round window – a perilymph pressure regulator?On a novel mechanoreceptor‐like neuron in the human round window membrane. ACTA ACUST UNITED AC 2009. [DOI: 10.1080/16513860410018213] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Akagi N, Takumida M, Anniko M. Effect of inner ear blood flow changes on the endolymphatic sac. Acta Otolaryngol 2008; 128:1187-95. [PMID: 18607967 DOI: 10.1080/00016480801910387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
CONCLUSIONS That the endolymphatic sac (ES) reacts to changes in inner ear blood flow may be important for homeostasis of the inner ear fluid volume and pressure. OBJECTIVES To elucidate the effect of changes in inner ear blood flow on the ES and to learn more about the volume and pressure regulatory function of the ES. MATERIALS AND METHODS Epinephrine or sodium nitroprusside (SNP) was injected into the middle ear cavity of adult CBA/J mice. The ES were analyzed morphologically by light microscopy. RESULTS Epinephrine reduced the luminal size of the ES leading to an accumulation of intraluminal homogeneous substance. Injection of SNP increased the size of the ES lumen, accompanied by a collapse of the lateral intercellular space (LIS) and dense perisaccular tissue. These changes were almost reversed 4 h after injection.
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Affiliation(s)
- Nana Akagi
- Hiroshima University School of Medicine, Hiroshima, Japan
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Akagi N, Takumida M, Anniko M. Effect of acute endolymphatic hydrops overload on the endolymphatic sac. Acta Otolaryngol 2008; 128:239-44. [PMID: 17851910 DOI: 10.1080/00016480701497428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
CONCLUSIONS Homeostasis of endolymph volume is a complex mechanism, in which the endolymphatic sac (ES) may play an important role. OBJECTIVES To elucidate the effect of acute endolymphatic hydrops (EH) on the ES and to gain further information about the volume and pressure regulative function of the ES. MATERIALS AND METHODS Distilled water was injected into the middle ear cavity of adult CBA/J mice. The ESs were studied morphologically by light and transmission electron microscopy. RESULTS Mild EH was found, particularly in the upper turn of the cochlea. Acute EH led to an increase in the size of the ES lumen, accompanied by collapse of the lateral intercellular spaces and dense perisaccular tissue, changes which had reversed 2 h after the injection.
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Affiliation(s)
- Nana Akagi
- Hiroshima University School of Medicine, Hiroshima, Japan
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Abstract
BACKGROUND Gene therapy may provide a way to restore cochlear function to deaf patients. The most successful techniques for cochlear gene therapy have been injection of early-generation adenoviral vectors into scala media in guinea pigs. However, it is important to be able to perform gene therapy research in mice because there is wide availability of transgenic strains with hereditary hearing loss. PURPOSE We demonstrate our technique for delivery of a third-generation adenoviral vector, helper-dependent adenovirus (HDAd), to the adult mouse cochlea. METHODS Mice were injected with an HDAd that contained a reporter gene for either beta-galactosidase or green fluorescent protein into scala media. After 4 days, the cochleae were harvested for analyses. Auditory brainstem response monitoring of cochlear function was performed before making a cochleostomy, after making a cochleostomy, and before killing the animal. RESULTS Beta-galactosidase was identified in the spiral ligament, the organ of Corti, and spiral ganglion cells by light microscopy. Green fluorescent protein epifluorescence was assessed in whole-mount organ of Corti preparations using confocal microscopy. This demonstrated transduction of inner hair cells, outer hair cells, and supporting cells. Paraffin-embedded cross sections similarly revealed gene transduction within the organ of Corti. Threshold shifts of 39.8 +/- 5.4 and 37.7 +/- 5.5 dB were observed in mice injected with HDAd or control buffer, respectively. CONCLUSION The technique of scala media HDAd injection reliably infects the adult mouse cochlea, including cells within the organ of Corti, although the procedure itself adversely affects hearing.
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Affiliation(s)
- S Plontke
- Klinik für Hals-, Nasen- und Ohrenheilkunde, Kopf- und Halschirurgie, Universitätsklinikum Tübingen, 72076, Tübingen.
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Ishida T, Hatae T, Nishi N, Araki N. Soluble megalin is accumulated in the lumen of the rat endolymphatic sac. Cell Struct Funct 2006; 31:77-85. [PMID: 17063000 DOI: 10.1247/csf.06013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The endolymphatic sac (ES) is believed to play an important role in maintaining homeostasis in the inner ear by the absorption and endocytosis of endolymph. Megalin is a 600-kDa multiligand endocytic receptor expressed in certain types of absorptive epithelia including kidney proximal tubules. We analyzed the immunoreactivity for megalin in rat ES by immunofluorescence, immunogold electron microscopy, and immunoblotting. With immunostaining, the luminal substances of the ES were strongly stained for megalin. Megalin was also localized in luminal macrophage-like cells and both types of epithelial cell (mitochondria-rich cells and ribosome-rich cells). In these cells, the megalin was localized in the lumen of endosomes, but was not membrane associated. This localization pattern indicates that the megalin in these cells is not a membrane receptor, but merely one of the constituents that are endocytosed from the lumen of the ES. Immunoblotting indicated that the megalin in the ES is a 210-kDa molecule lacking a cytoplasmic domain. This suggests that the megalin in the ES may be a soluble form, different from the 600-kDa membrane-bound receptor expressed in kidneys. Taken together, it is likely that the megalin in the ES lumen is a soluble component and may be endocytosed by the ES epithelial cells. Furthermore, we found that the tectorial membrane, an acellular structure in the cochlea, gave a strong megalin immunoreaction. Since the cochlea is connected to the ES, the megalin may be transported alone or with the components of the tectorial membrane from the cochlea to the ES lumen through longitudinal flow.
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Affiliation(s)
- Tetsuya Ishida
- Department of Histology and Cell Biology, School of Medicine, Kagawa University, Miki, Kagawa 761-0793, Japan.
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Bergenius J, Tomanovic T. Persistent geotropic nystagmus--a different kind of cupular pathology and its localizing signs. Acta Otolaryngol 2006; 126:698-704. [PMID: 16803707 DOI: 10.1080/00016480500475609] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
CONCLUSION A persistent geotropic positional nystagmus indicates a dysfunction in the lateral semicircular canal with a cupula of less specific weight than the surrounding endolymph. It is possible to determine the side of the affected cupula by recording the nystagmus pattern in yaw and pitch plane. OBJECTIVES To identify the clinical features in patients with a persistent geotropic positional nystagmus, establish lateralizing signs and relate the findings to a pathophysiologic mechanism. PATIENTS AND METHODS Six patients with acute onset vertigo of a peripheral origin and persistent geotropic nystagmus were examined with videonystagmoscopy and the nystagmus characteristics in different positions of the head in yaw and pitch plane were studied. RESULTS Besides the persistent geotropic nystagmus, a zero zone was found with no nystagmus, beyond which the nystagmus changed direction when the head of the patient in supine position was gradually rotated from side to side. The zero zone was present when the head was turned slightly towards one side and is thought to represent a position where the affected cupula is aligned with the gravitational vertical. With the head bent forwards the nystagmus direction was to the non-affected side and when the head was bent backwards to the affected side.
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Affiliation(s)
- Johan Bergenius
- Department of Audiology, Karolinska University Hospital, Stockholm, Sweden
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Hultgård-Ekwall AK, Mayerl C, Rubin K, Wick G, Rask-Andersen H. An interstitial network of podoplanin-expressing cells in the human endolymphatic duct. J Assoc Res Otolaryngol 2006; 7:38-47. [PMID: 16408168 PMCID: PMC2504586 DOI: 10.1007/s10162-005-0021-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2005] [Accepted: 11/11/2005] [Indexed: 10/25/2022] Open
Abstract
The human endolymphatic duct (ED) with encompassing interstitial connective tissue (CT) is believed to be important for endolymph resorption and fluid pressure regulation of the inner ear. The periductal CT cells are interconnected via numerous cellular extensions, but do not form vessel structures. Here we report that the periductal CT is populated by two distinct cell phenotypes; one expressing podoplanin, a protein otherwise found on lymph endothelia and on epithelia involved in fluid fluxes, and a second expressing a fibroblast marker. A majority of the interstitial cells expressed podoplanin but not the lymphatic endothelial cell markers hyaluronan receptor (LYVE-1) or vascular endothelial growth factor receptor-3 (VEGFR-3). The fibroblast marker positive cells were found close to the ED epithelium. In the mid- and distal parts of the ED, these cells were enriched under folded epithelia. Furthermore, subepithelial CT cells were found to express activated platelet derived growth factor (PDGF)-beta receptors. Cultured CT cells from human inner ear periductal and perisaccular explant tissues were identified as fibroblasts. These cells compacted a three-dimensional collagen lattice by a process that could be promoted by PDGF-BB, a factor involved in interstitial fluid pressure regulation. Our results are compatible with the notion that the periductal CT cells are involved in the regulation of inner ear fluid pressure. By active compaction of the periductal CT and by the formation of villous structures, the CT cells could modulate fluid fluxes over the ED epithelium as well as the longitudinal flow of endolymph in the ED.
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Affiliation(s)
- Anna-Karin Hultgård-Ekwall
- Department of Medical Biochemistry and Microbiology, Uppsala University, BMC, Box 582, SE-751 23, Uppsala, Sweden.
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Valk WL, Wit HP, Segenhout JM, Dijk F, van der Want JJL, Albers FWJ. Morphology of the endolymphatic sac in the guinea pig after an acute endolymphatic hydrops. Hear Res 2005; 202:180-7. [PMID: 15811710 DOI: 10.1016/j.heares.2004.10.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2004] [Accepted: 10/21/2004] [Indexed: 11/25/2022]
Abstract
The role of the endolymphatic sac (ES) in endolymph volume homeostasis is speculative. The present study investigates changes of the ES's epithelia and luminal filling after induction of an acute endolymphatic hydrops. After microinjection of 1.1 mul artificial endolymph into scala media of the cochlea, guinea pigs were terminated immediately (n = 6) or after different time intervals ; 1/2 h (n = 3), 1 h (n = 4) and 2 h (n = 4). Inner ear specimens were processed for light and/or transmission electron microscopy. The non-injected contralateral ear served as a histological control. Correct injection was confirmed by detection of microspheres in the endolymphatic compartment after the same microinjection procedure. In all specimens, ribosome rich cells and intraluminal macrophages appeared to be actively involved in degradation of homogeneous substance (HS) by secreting lytic enzymes and digestion, respectively. Amazingly, in our study no ES differences were found between injected and non-injected ears and no distinct changes were observed in guinea pigs terminated after different time intervals. The ES's luminal HS was always present and often to a large extent. This is in contrast with [Hear. Res. 138, 81] dramatic changes were observed. Endolymph volume homeostasis is a complex mechanism, in which the role of HS remains obscure.
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Affiliation(s)
- W L Valk
- Department of Otorhinolaryngology, University Hospital Groningen, Netherlands.
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27
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Valk WL, Wit HP, Albers FWJ. Evaluation of cochlear function in an acute endolymphatic hydrops model in the guinea pig by measuring low-level DPOAEs. Hear Res 2004; 192:47-56. [PMID: 15157962 DOI: 10.1016/j.heares.2003.12.021] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2003] [Accepted: 12/09/2003] [Indexed: 11/17/2022]
Abstract
During and after microinjection of artificial endolymph into scala media of the guinea pig, the 2f1- f2 -DPOAE at 4.5 kHz generated by low-level primaries was recorded. Reproducible changes were measured when 1.1 microl of artificial endolymph was injected at a rate of 1.65 nl/s (1.53-1.83). This volume corresponds with an acute endolymphatic hydrops of 23%. After the onset of injection the inner ear pressure immediately increased to a mean higher level of 22 Pa, whereas the 2f1- f2 -amplitude and -phase did not change for about 1 min. Thereafter, the amplitude decreased 2.6 dB (+/- 0.7) on average and slowly regained almost its initial value, with recovery frequently starting within the period of injection. In an attempt to explain the observed changes in 2f1- f2 -amplitude the basilar membrane displacement towards scala tympani at the 2f1- f2 generation site is estimated to be 19 nm for a 1.1 microl increase of endolymph volume. A small deflection of the outer hair cell stereocilia and as a consequence a change in cell conductance may explain the 2f1- f2 -amplitude changes. However, the precise mechanism of cochlear function change caused by endolymph volume increase (hydrops) remains to be elucidated.
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Affiliation(s)
- Willem L Valk
- Department of Otorhinolaryngology, University Hospital Groningen, P.O. Box 30.001, 9700 RB Groningen, The Netherlands.
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Salt AN, Rask-Andersen H. Responses of the endolymphatic sac to perilymphatic injections and withdrawals: evidence for the presence of a one-way valve. Hear Res 2004; 191:90-100. [PMID: 15109708 DOI: 10.1016/j.heares.2003.12.018] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2003] [Accepted: 12/30/2003] [Indexed: 11/23/2022]
Abstract
Although the endolymphatic sac (ES) is thought to be a primary site for endolymph volume regulation, we have limited knowledge of how it responds to volume and pressure changes. In a prior publication, we demonstrated changes of K(+), Na(+) and endolymphatic sac potential (ESP) resulting from volume injections into, and withdrawals from, scala media of the cochlea. In the present study, we compared the influence of injections into and withdrawals from scala tympani of the cochlea on the endolymphatic sac. It is assumed that similar pressure changes are induced in endolymph and perilymph of both the cochlear and vestibular compartments of the ear. Pressure changes induced by the perilymphatic injections and withdrawals did not induce similar K(+) changes in the ES. The majority of perilymph withdrawals caused K(+) and ESP reductions in the sac, but few injections caused any measurable changes in the sac. Pressure measurements from the ES demonstrated that transmission of labyrinthine pressures to the lumen was directionally sensitive, with negative pressure transmitted more effectively than positive. In other experiments, application of infrasonic stimulation to the ear canal resulted in K(+) increase in the ES. These physiological measurements suggest that the endolymphatic duct may be closed by sustained positive pressure in the vestibule but open during pressure fluctuations. Study of the anatomy where the endolymphatic duct enters the vestibule suggests that the membranous sinus of the endolymphatic duct could act as a mechanical valve, limiting the flow of endolymph from the saccule to the endolymphatic sac when pressure is applied. This structure could therefore play an important role in endolymph volume regulation.
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Affiliation(s)
- Alec N Salt
- Department of Otolaryngology, Box 8115, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
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Peters TA, Tonnaer ELGM, Kuijpers W, Curfs JHAJ. Changes in ultrastructural characteristics of endolymphatic sac ribosome-rich cells of the rat during development. Hear Res 2003; 176:94-104. [PMID: 12583884 DOI: 10.1016/s0378-5955(02)00748-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It has recently been demonstrated that endolymphatic sac (ES) ribosome-rich (dark) cells respond to induced endolymph changes and are thus likely to be involved in endolymph homeostasis. Therefore, we studied the ultrastructural characteristics of rat ES ribosome-rich cells during development in order to determine the cellular distribution of organelles involved in protein metabolism, secretion and absorption, indicative for their contribution to endolymph homeostasis. During embryonal stages ribosome-rich cells contain a limited number and variety of organelles and are predominantly involved in the production of components for cell growth and differentiation. In the young adult stage (P60) three different states of ribosome-rich cells may be distinguished. State A resembles a cell with only limited metabolic activities whereas state B is characterized by numerous different intracellular organelles and is considered to be involved in production and secretion as well as absorption and degradation of complex proteins. A third cellular state, state C, is filled with phagolysosomes and contains very few other organelles. This is considered to be a final (pre)apoptotic state. Autoradiography data suggest that ES ribosome-rich cells are capable of synthesis and secretion of tyrosine-containing proteins and may thus be involved in regulation of the osmolarity of endolymph based on the capacity to bind cations as well as water molecules. In addition, ES ribosome-rich cells appear to synthesize and secrete fucosylated glycoproteins into the endolymph. In conclusion, the present data suggest that ES ribosome-rich cells are actively involved in endolymph homeostasis through secretion and absorption of complex proteins and it is hypothesized that they are able to adapt their function or activities in response to changes in endolymph composition.
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Affiliation(s)
- Theo A Peters
- Department of Otorhinolaryngology, University Medical Center St Radboud, Philips van Leydenlaan 15, 6500 HB Nijmegen, The Netherlands.
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Abstract
The endolymphatic sac is believed to represent one of the primary loci for endolymph volume regulation in the inner ear. Quantitative analysis of physiologic measurements from the endolymphatic sac requires knowledge of the anatomy of the structure, specifically the luminal volume and the variation of cross-sectional area with distance along the sac. Recently techniques have become available to make these measurements. In the present study, fixed, isolated specimens of the guinea pig endolymphatic sac were imaged by high-resolution magnetic resonance microscopy (MRM) or by histological serial sections. Structures were reconstructed and quantified using image analysis software. In specimens imaged by MRM the endolymphatic sac volume, including tissue and lumen, was 359 nl for the intraosseous region and 106 nl for the extraosseous region, totaling 465 nl for the entire structure. The luminal volumes were 131 nl for the intraosseous region and 13 nl for the extraosseous region, totaling 144 nl. In histological specimens the volume, including tissue and lumen, was 414 nl for the intraosseous region and 121 nl for the extraosseous region, totaling 535 nl for the entire structure. The luminal volumes were 152 nl for the intraosseous region and 26 nl for the extraosseous region, totaling 179 nl. Differences in volume estimates obtained by the two methods were not statistically significant and variation was dominated by inter-specimen variation. Pooling the data, the total volume of the endolymphatic sac in the guinea pig including tissue and lumen was 506 nl (S.D. 100, n=17) and the volume of the lumen was 169 nl (S.D. 48, n=14).
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Affiliation(s)
- Kelli Pettit
- Department of Otolaryngology, Box 8115, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
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Peters TA, Tonnaer ELGM, Kuijpers W, Cremers CWRJ, Curfs JHAJ. Differences in endolymphatic sac mitochondria-rich cells indicate specific functions. Laryngoscope 2002; 112:534-41. [PMID: 12148867 DOI: 10.1097/00005537-200203000-00023] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE/HYPOTHESIS The purpose of the study was to examine the specific involvement of endolymphatic sac mitochondria-rich cells in endolymph homeostasis. STUDY DESIGN Transmission electron microscopy and immunohistochemistry were performed on the endolymphatic sac of young adult rats, and two important developmental stages were also investigated. METHODS Ultrastructural characteristics of endolymphatic sac mitochondria-rich cells were studied more concisely and compared with renal mitochondria-rich cells (i.e., the intercalated cells). In addition, expression of cytokeratins 7 and 19 was determined. RESULTS Until birth, only one type of mitochondria-rich cell is observed in the rat endolymphatic sac. In young adult animals, distinct differences in mitochondria-rich cell ultrastructure in the endolymphatic sac enables classification into subtypes or configurations. Comparison of endolymphatic sac mitochondria-rich cells with renal intercalated cells reveals striking similarities and provides additional information on their specific function in endolymph homeostasis. Furthermore, differences in cytokeratin expression are determined in endolymphatic sac mitochondria-rich cells. CONCLUSIONS Differences in morphology of endolymphatic sac mitochondria-rich cells develop after birth and may reflect a distinct functional or physiological state of the cell. In analogy to renal intercalated cells, the distribution patterns of H+-adenosine triphosphatase and Cl-/HCO3- exchanger may differ between subtypes. We propose that subtype A mitochondria-rich cells, from which protruding A mitochondria-rich cells are the activated state, are involved in proton secretion (apical H+-adenosine triphosphatase) and thus are potential candidates for hearing loss accompanying renal tubular acidosis. Subtype B mitochondria-rich cells are the most likely candidates to be affected in Pendred syndrome because of the assumed function of pendrin as apical Cl-/HCO3- exchanger.
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Affiliation(s)
- Theo A Peters
- Department of Otorhinolaryngology, University Medical Center St Radboud, Nijmegen, The Netherlands.
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Friberg U, Rask-Andersen H. Vascular occlusion in the endolymphatic sac in Meniere's disease. Ann Otol Rhinol Laryngol 2002; 111:237-45. [PMID: 11913684 DOI: 10.1177/000348940211100308] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In 2 patients with severe Meniere's disease (MD), there was histologic evidence of occlusion of the vein of the vestibular aqueduct (VVA). This finding coincided with total or partial occlusion of numerous small vessels around the endolymphatic sac (ES), flattening of epithelium, extensive perisaccular fibrosis, and signs of new bone formation. Ultrastructural analysis of the occluding material showed foci with dense connective tissue, calcification, lipid deposits, and layers of basement membrane, sometimes concentrically arranged. The exact nature of the occluding material was unknown. In another 2 MD patients, the VVA was not visualized, and the ES vessels showed no signs of occlusion. Seven controls with acoustic schwannoma or meningioma had normal vasculature. The presence of vascular impairment in the ES in MD patients indicated that altered hemodynamics may contribute to the pathogenesis of endolymphatic hydrops and MD.
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Affiliation(s)
- Ulla Friberg
- Department of Otorhinolaryngology-Head and Neck Surgery, Uppsala University Hospital, Sweden
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Linder B, Boström M, Gerdin B, Rask-Andersen H. In vitro growth of human endolymphatic sac cells: a transmission electron microscopic and immunohistochemical study in patients with vestibular schwannoma and Ménière's disease. Otol Neurotol 2001; 22:938-43. [PMID: 11698823 DOI: 10.1097/00129492-200111000-00039] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
HYPOTHESIS Human endolymphatic sac cells have been notoriously difficult to maintain in culture. It was hypothesized that an in vitro environment intended for growth of keratinocytes would also be suitable for human endolymph sac cells. BACKGROUND Studies on cell physiology of human endolymphatic sac cells have been hampered by difficulties in maintaining them in culture. METHODS Human endolymphatic sac cells were taken from 10 patients during translabyrinthine skull base surgery for vestibular schwannoma, one of whom also had Ménière's disease. Cell lines of proliferating epithelial cells were obtained after trypsinization and growth in a 3:1 mixture of Dulbecco's modified Eagle medium and Ham's F12 medium supplemented with 10% fetal calf serum. Fibroblast overgrowth was counteracted by the use of so-called cloning rings. During various stages, cells were investigated with transmission electron microscopy and/or immunohistochemistry. RESULTS Proliferation took place after 2 to 3 days of primary cell culture. The cells were cytokeratin-positive and pleomorphic, and they had abundant polarized microvillus-like projections, numerous coated cytoplasmic pits and vesicles, and a well-developed rough endoplasmic reticulum. CONCLUSION Cell lines of proliferating human endolymphatic sac cells can be produced with the technique described here and may be a valid tool in studies of human endolymph sac physiology.
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Affiliation(s)
- B Linder
- Department of Otolaryngology, University Hospital, S-751 85 Uppsala, Sweden
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Abstract
Direct measurements of the dispersal of markers in endolymph have failed to support previously established hypotheses of endolymph homeostasis, specifically longitudinal flow, radial flow, and dynamic flow theories. Rather, they suggest that in the normal state endolymph is maintained without a significant involvement of volume flow at all. Ions appear to be transported into and out of the endolymphatic space in a similar manner to that for a single cell, with each ion transport process contributing to the electrolyte pool. In abnormal volume states, however, longitudinal volume flow of endolymph may contribute to homeostasis. Procedures that enlarge the endolymphatic space result in endolymph flow toward the base of the cochlea, contributing to the removal of electrolytes and volume. Similarly, procedures that decrease cochlear endolymph volume induce apically directed flow in the cochlea, contributing to the addition of electrolytes and volume to the endolymphatic space. The endolymphatic sac responds to endolymph volume disturbance, showing op posite responses to volume increases and decreases. Although evidence is still limited, the endolymphatic sac appears to act as a "bidirectional overflow" system. While volume disturbances originating from out-of-balance transport processes anywhere in the labyrinth may be corrected by the sac, dysfunction of the sac itself is likely to have a substantial effect on endolymph status.
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Affiliation(s)
- A N Salt
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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35
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Abstract
The Reissner's membrane (RM) was visualised by confocal microscopy in the isolated temporal bone of the guinea pig. The function of the organ was followed by measuring its physiological response. Static pressure applied in the basal coil caused a distention of the RM in the apical coil into the scala vestibuli. The sensitivity to a test tone was reduced. When the pressure was relieved, the RM returned to its original position and the response recovered. If the increased pressure was maintained, the RM would bulge further. The RM could then be reversibly stretched and return gradually, with a delay, to its original position. Alternatively, it could be over-stretched and return with an over-shoot past its original position toward the organ of Corti. In response to repetitive tone pulses of above 80 dB, hydrops of the RM also developed. This was accompanied by a reduced sensitivity. A slow recovery to the original position, or over-shoot, and return of responsiveness could be seen. Above 106 dB sustained loss was generally seen. It is concluded that the RM can accommodate increased scala media pressure by distention. This will relieve the organ of Corti from part of the pressure and may protect the organ from trauma.
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Affiliation(s)
- A Flock
- Department of Physiology and Pharmacology, Division of Physiology II, Karolinska Institutet, S-171 77, Stockholm, Sweden.
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36
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Abstract
The endolymphatic sac (ES) is believed to be the locus for endolymph volume regulation in the inner ear. It has recently been shown that induced endolymph volume changes in the cochlea result in anatomical changes in the ES, suggesting that function of the sac varies according to endolymph volume status. In the present study we have recorded luminal concentrations of K(+) and Na(+) from the ES and the endolymphatic sac potential (ESP) during cochlear endolymph volume changes. ES recordings were made by an extradural approach, thereby preserving normal cerebrospinal fluid resting pressure. Cochlear endolymph volume changes were generated by performing injections or withdrawals through a pipette inserted into endolymph by a round window approach. The pre-treatment concentrations of K(+) and Na(+) in the ES were found to be 8.4 mM (S.D. 3.3, n=8) and 128. 6 mM (S.D. 18.4, n=10) respectively, and the mean ESP was 14.4 mV (S. D. 5.2, n=18). Endolymphatic injections were found to produce a sustained increase in the K(+) content of the ES by an average of 19. 9 mM and to decrease Na(+) by 30.7 mM measured 50 min after the start of injection. The time for K(+) increase to occur was found to correlate with the injected volume, with larger injected volumes producing a more rapid increase. Endolymphatic withdrawals were found to induce a slow decline in endolymphatic K(+) by an average of 3.4 mM measured at 50 min after withdrawal, although no significant change of Na(+) was detected. Volume-induced ESP changes were highly variable. Injections produced a small increase in the mean ESP and withdrawals produced a small decrease but neither change was statistically significant and some animals showed potential changes in the opposite direction. These data show that a change in cochlear endolymph volume status results in a physiologic response of the ES which is sustained for a considerable period. If the ES plays a part in the restoration of normal endolymph volume, this process appears to proceed slowly, based on the prolonged time courses of ionic changes observed.
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Affiliation(s)
- A N Salt
- Department of Otolaryngology, Box 8115, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
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37
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Danckwardt-Lillieström N, Friberg U, Kinnefors A, Rask-Andersen H. Ultrastructural analysis of 20 intraosseous endolymphatic sacs from patients with cerebello-pontine angle tumours. A surgically obtained control material for histopathological studies. Auris Nasus Larynx 2000; 27:311-21. [PMID: 10996489 DOI: 10.1016/s0385-8146(00)00073-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVE The purpose of this work was to collect a surgically obtained, freshly fixed material of the human intraosseous endolymphatic sac. This biopsy material was used to describe the normal ultrastructure as well as to serve as a control material for histopathological studies on Ménière's disease in particular. METHOD The specimens, obtained during surgery for cerebello-pontine angle tumours, were fixed by immersion and then prepared by routine methods for transmission electron microscopy. The ultrastructural analysis was focused on intraluminal content, epithelial cell layer, subepithelial space, and morphological signs of immunological activity. The ultrastructure was analysed in relation to inner ear sensory function, tumour diagnosis, and patient's age and sex. RESULTS As it was possible to obtain numerous specimens with an intact bony shell, the intraluminal substance could be analysed. Two separate epithelial cell types are described: one less abundant, often lighter and mitochondria-rich cell type; the other, often darker, epithelial cell with fever mitochondrias. Some of the latter cell types showed signs of active secretion. The subepithelial space was characterized by loose connective tissue adjacent to the epithelial lining, being more dense toward the bone. Elastic fibres were seen surrounding the entire endolymphatic sac. Macrophages in the intraluminal space and lymphocytes in the epithelial and subepithelial layers are described. No distinct morphology correlating to inner ear sensory function, tumour diagnosis, or patient's age and sex was revealed. CONCLUSIONS This study confirms previously described, extensive variations in form and structure of the human endolymphatic sac. Various factors, such as surgical trauma, previous treatment, and processing method, can affect the ultrastructure and must be taken into consideration. The specimens described in this work appear to constitute a good control material for histopathological study of the human endolymphatic sac. It is still necessary to obtain large control materials such as this, as surgical specimens from patients with Ménière's disease are uncommon.
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Affiliation(s)
- N Danckwardt-Lillieström
- Department of Oto-Rhino-Laryngology and Head & Neck Surgery, University Hospital, 751 85, Uppsala, Sweden.
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