Development of Monovalent Ions in the Endolymph in Mouse Cochlea

Yamasaki, Masayuki; Komune, Shizuo; Shimozono, Masami; Matsuda, Keiji; Haruta, Atsushi

doi:10.1159/000027753

Cited by 36 publications

(33 citation statements)

References 18 publications

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“…The only other study regarding [K + ] e measurement in mice yielded an unusually high [K + ] e in adult ICR strain mice: 200 mM (Yamasaki et al 2000). The basis for the difference from our results is not presently known.…”

Section: Discussioncontrasting

confidence: 96%

Age-Related Changes in Cochlear Endolymphatic Potassium and Potential in CD-1 and CBA/CaJ Mice

Marcus

2003

JARO - Journal of the Association for Research in Otolaryngolog

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The CD-1 mouse strain is known to have early onset of hearing loss that is progressive with aging. We sought to determine whether a disturbance of K + homeostasis and pathological changes in the cochlear lateral wall were involved in the age-related hearing loss (AHL) of CD-1 as compared to the CBA/CaJ strain which has minimal AHL. In the present study, the endocochlear potential (EP) and endolymphatic K + concentration ([K + ] e ) were measured in both strains of mice with double-barrel microelectrodes at ''young'' (1-2 mo) and ''old'' (5-9 mo) ages. CBA/ CaJ mice displayed no changes with aging in EP and [K + ] e of the basal turn. In the apical turn, there was a small positive shift of the EP (10 mV) with aging under both normoxic and acute anoxic conditions ()EP), without any change of [K + ] e . Further, there were no obvious pathological changes in the lateral wall of CBA/CaJ mice. By contrast, old CD-1 mice displayed a significantly reduced [K + ] e by 30% in both basal and apical turns with no significant changes in normoxic EP. The )EP in the apical turn was significantly reduced in magnitude by 6 mV. A severe loss of cells with aging was observed in the region of type IV fibrocytes of the apical and basal turns and of type II fibrocytes in the basal turn. A complete degeneration of organ of Corti was also observed at the basal turn of old CD-1 mice, as well as a basalward decline of spiral ganglion neuron density. The pathological changes in spiral ligament of CD-1 mice were similar to those of an inbred mouse strain C57BL/6J that expresses an AHL gene (ahl) and might be a primary etiology of AHL of CD-1 mice. These findings have ramifications for our understanding of AHL and for interpretation of genetic mutations in a CD-1 background.

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Section: Discussioncontrasting

confidence: 96%

Age-Related Changes in Cochlear Endolymphatic Potassium and Potential in CD-1 and CBA/CaJ Mice

Marcus

2003

JARO - Journal of the Association for Research in Otolaryngolog

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“…The EP and [K + ] in the cochlear endolymph of wild-type mice [basal turn: 96.2 ± 3.9 mV, 113.0 ± 10.9 mM (n = 6); apical turn: 92.3 ± 2.6 mV, 120.0 ± 7.8 mM (n = 6); Fig. 6b] were similar to values reported previously (Marcus et al 2002;Sadanaga and Morimitsu 1995;Yamasaki et al 2000). In Pds )/) mice, the EP was dramatically reduced in both the basal [)15.0 ± 5.0 mV (n = 5)] and apical [)2.5 ± 0.…”

Section: Measurement Of Endolymphatic Potential and Potassium Levelssupporting

confidence: 88%

Localization and Functional Studies of Pendrin in the Mouse Inner Ear Provide Insight About the Etiology of Deafness in Pendred Syndrome

Royaux

Belyantseva

et al. 2003

JARO - Journal of the Association for Research in Otolaryngolog

140

149

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Immunolocalization studies of mouse cochlea and vestibular end-organ were performed to study the expression pattern of pendrin, the protein encoded by the Pendred syndrome gene (PDS), in the inner ear. The protein was restricted to the areas composed of specialized epithelial cells thought to play a key role in regulating the composition and resorption of endolymph. In the cochlea, pendrin was abundant in the apical membrane of cells in the spiral prominence and outer sulcus cells (along with their root processes). In the vestibular end-organ, pendrin was found in the transitional cells of the cristae ampullaris, utriculi, and sacculi as well as in the apical membrane of cells in the endolymphatic sac. Pdsknockout (Pds )/) ) mice were found to lack pendrin immunoreactivity in all of these locations. Histological studies revealed that the stria vascularis in Pds )/) mice was only two-thirds the thickness seen in wildtype mice, with the strial marginal cells showing irregular shapes and sizes. Functional studies were also performed to examine the role of pendrin in endolymph homeostasis. Using double-barreled electrodes placed in both the cochlea and the utricle, the endocochlear potential and endolymph potassium concentration were measured in wild-type and Pdsmice. Consistent with the altered strial morphology, the endocochlear potential in Pds )/) mice was near zero and did not change during anoxia. On the other hand, the endolymphatic potassium concentration in Pds )/) mice was near normal in the cochlea and utricle. Together, these results suggest that pendrin serves a key role in the functioning of the basal and/ or intermediate cells of the stria vascularis to maintain the endocochlear potential, but not in the potassium secretory function of the marginal cells.

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“…However, it is more likely that the loss of Sox9 expression is secondary to a prior differentiation defect of the otic mesenchyme. Intriguingly, Cx26 expression in this domain precedes the onset of K + -cycling through the gap junction network of the spiral ligament (Sadanaga et al, 1995;Yamasaki et al, 2000). Hence, the expression of Cx26 might indicate a role in…”

Section: Discussionmentioning

confidence: 95%

Deafness in mice lacking the T-box transcription factor Tbx18 in otic fibrocytes

et al. 2008

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In the cochlea, fibrocytes play important physiological roles, including the maintenance of the ionic composition of the endolymph. Human deafness upon fibrocyte alterations witnesses their crucial role for hearing. We demonstrate that differentiation of otic fibrocytes requires the T-box transcription factor gene Tbx18. Tbx18 expression during inner ear development is restricted to the sub-region of otic mesenchyme that is fated to differentiate into fibrocytes. We rescued the somitic defect that underlies the perinatal lethality of Tbx18-mutant mice by a transgenic approach, and measured auditory brainstem responses. Adult Tbx18-deficient mice showed profound deafness and a complete disruption of the endocochlear potential that is essential for the transduction of sound by sensory hair cells. The differentiation of otic fibrocytes of the spiral ligament was severely compromised. Tissue architecture of the stria vascularis of the lateral wall was disrupted, exhibiting an almost complete absence of the basal cell layer,and a reduction and changes of intermediate and marginal cells, respectively. Stria vascularis defects resulted from the failure of Tbx18-mutant otic fibrocytes to generate the basal cell layer by a mesenchymal-epithelial transition. Defects in otic fibrocyte differentiation may be subordinate to a primary role of Tbx18 in early compartmentalization of the otic mesenchyme, as lineage restriction and boundary formation between otic fibrocytes and the surrounding otic capsule were severely affected in the mutant. Our study sheds light on the genetic control of patterning and differentiation of the otic mesenchyme, uncovers distinct steps of stria vascularis formation and illuminates the importance of non-epithelially-derived otic cell types for normal hearing and the etiology of deafness.

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Development of Monovalent Ions in the Endolymph in Mouse Cochlea

Cited by 36 publications

References 18 publications

Age-Related Changes in Cochlear Endolymphatic Potassium and Potential in CD-1 and CBA/CaJ Mice

Age-Related Changes in Cochlear Endolymphatic Potassium and Potential in CD-1 and CBA/CaJ Mice

Localization and Functional Studies of Pendrin in the Mouse Inner Ear Provide Insight About the Etiology of Deafness in Pendred Syndrome

Deafness in mice lacking the T-box transcription factor Tbx18 in otic fibrocytes

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