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Immunolocalization of calcium sensing and transport proteins in the murine endolymphatic sac indicates calciostatic functions within the inner ear


Bächinger, David; Egli, Hannes; Goosmann, Madeline M; Monge Naldi, Arianne; Eckhard, Andreas H (2019). Immunolocalization of calcium sensing and transport proteins in the murine endolymphatic sac indicates calciostatic functions within the inner ear. Cell and Tissue Research, 378(2):163-173.

Abstract

An exceptionally low calcium (Ca2+) concentration in the inner ear endolymph ([Ca2+]endolymph) is crucial for proper auditory and vestibular function. The endolymphatic sac (ES) is believed to critically contribute to the maintenance of this low [Ca2+]endolymph. Here, we investigated the immunohistochemical localization of proteins that are presumably involved in the sensing and transport of extracellular Ca2+ in the murine ES epithelium. Light microscopic and fluorescence immunolabeling in paraffin-embedded murine ES tissue sections (male C57BL/6 mice, 6–8 weeks old) demonstrated the presence of the calcium-sensing receptor CaSR, transient receptor potential cation channel subtypes TRPV5 and TRPV6, sarco/endoplasmic reticulum Ca2+-ATPases SERCA1 and SERCA2, Na+/Ca2+ exchanger NCX2, and plasma membrane Ca2+ ATPases PMCA1 and PMCA4 in ES epithelial cells. These proteins exhibited (i) membranous (apical or basolateral) or cytoplasmic localization patterns, (ii) a proximal-to-distal labeling gradient within the ES, and (iii) different distribution patterns among ES epithelial cell types (mitochondria-rich cells (MRCs) and ribosome-rich cells (RRCs)). Notably, in the inner ear membranous labyrinth, CaSR was exclusively localized in MRCs, suggesting a unique role of the ES epithelium in CaSR-mediated sensing and control of [Ca2+]endolymph. Structural loss of the distal ES, which is consistently observed in Meniere’s disease, may therefore critically disturb [Ca2+]endolymph and contribute to the pathogenesis of Meniere’s disease.

Abstract

An exceptionally low calcium (Ca2+) concentration in the inner ear endolymph ([Ca2+]endolymph) is crucial for proper auditory and vestibular function. The endolymphatic sac (ES) is believed to critically contribute to the maintenance of this low [Ca2+]endolymph. Here, we investigated the immunohistochemical localization of proteins that are presumably involved in the sensing and transport of extracellular Ca2+ in the murine ES epithelium. Light microscopic and fluorescence immunolabeling in paraffin-embedded murine ES tissue sections (male C57BL/6 mice, 6–8 weeks old) demonstrated the presence of the calcium-sensing receptor CaSR, transient receptor potential cation channel subtypes TRPV5 and TRPV6, sarco/endoplasmic reticulum Ca2+-ATPases SERCA1 and SERCA2, Na+/Ca2+ exchanger NCX2, and plasma membrane Ca2+ ATPases PMCA1 and PMCA4 in ES epithelial cells. These proteins exhibited (i) membranous (apical or basolateral) or cytoplasmic localization patterns, (ii) a proximal-to-distal labeling gradient within the ES, and (iii) different distribution patterns among ES epithelial cell types (mitochondria-rich cells (MRCs) and ribosome-rich cells (RRCs)). Notably, in the inner ear membranous labyrinth, CaSR was exclusively localized in MRCs, suggesting a unique role of the ES epithelium in CaSR-mediated sensing and control of [Ca2+]endolymph. Structural loss of the distal ES, which is consistently observed in Meniere’s disease, may therefore critically disturb [Ca2+]endolymph and contribute to the pathogenesis of Meniere’s disease.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > University Hospital Zurich > Clinic for Otorhinolaryngology
Dewey Decimal Classification:610 Medicine & health
Uncontrolled Keywords:Pathology and Forensic Medicine, Cell Biology, Histology
Language:English
Date:1 November 2019
Deposited On:09 Aug 2019 07:54
Last Modified:27 Oct 2019 02:03
Publisher:Springer
ISSN:0302-766X
OA Status:Green
Publisher DOI:https://doi.org/10.1007/s00441-019-03062-2
Project Information:
  • : FunderSNSF
  • : Grant ID323530_183978
  • : Project TitleDevelopment of a new two-phase mouse model for Meniere’s disease
  • : FunderSNSF
  • : Grant ID1000-000001
  • : Project TitleSchlussband (Bd. VI) der Jacob Burckhardt-Biographie
  • : FunderSNSF
  • : Grant ID1000-000001
  • : Project TitleSchlussband (Bd. VI) der Jacob Burckhardt-Biographie

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