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PubMed1988

Computed tomography and magnetic resonance imaging of the inner ear.

The majority of temporal bone radiographic studies are obtained either for middle ear and mastoid disease or in the evaluation of retrocochlear pathology. With recent technologic advances, diagnostic imaging of the inner ear has developed an increasing role in the evaluation and management of diseases that affect the cochlea, semicircular canals, and the vestibular and cochlear aqueducts. High-resolution computed tomography (CT) provides excellent detail of the osseous labyrinth, whereas magnetic resonance imaging (MRI) generates images derived from the membranous labyrinth and its associated neural elements. Optimal techniques for obtaining high quality CT and MRI images of the normal and diseased inner ear are presented. CT has proved useful in the evaluation of inner ear malformations, cochlear otosclerosis, labyrinthine fistulization from cholesteatoma, translabyrinthine fractures, otic capsule osteodystrophies, in the assessment of cochlear patency before cochlear implantation, and in the localization of prosthetic devices such as stapes wires and cochlear implants. While MRI produces discernible images of the soft tissue and fluid components of the inner ear, it has yet to demonstrate any unique advantages in the evaluation of inner ear disease. However, MRI produces excellent and highly useful images of the audiovestibular and facial nerves, cerebellopontine angle, and brain.

Cholesteatoma↗
PubMed1990

A new model for photochemically induced thrombosis in the inner ear microcirculation and the use of hearing loss as a measure for microcirculatory disorders.

A new photochemical method was employed to cause disorders in the inner ear's microcirculation, using the rat as an animal model. Hearing loss was used as a measure for establishing the altered microcirculation. Under pentobarbital anesthesia, the middle ear was opened by a ventral approach. The lateral wall of the cochlea was then illuminated with a filtered xenon lamp (wavelength 540 nm) while rose bengal was infused intravenously. Photoactivated rose bengal produces oxygen radicals and oxygen singlets, which subsequently damage the vascular epithelium to cause the adhesion and aggregation of platelets in the small vessels. Disintegration of the inner ear hair cells at the irradiated site became evident 24 h after the illumination. These findings further suggest that the photochemical occlusion in the inner ear's microcirculation led to ischemic damage of the stria vascularis and the hair cells in the inner ear. When the action potential (AP) of the cochlea was measured with an electrocochleogram a gradual decrease occurred after the illumination. When acetylsalicylic acid was injected intravenously before treatment, the time required to completely suppress the AP was prolonged in a dose-dependent manner. Findings indicate that our method causes a photochemically induced occlusion in the inner ear's microcirculation and is therefore potentially useful for evaluating the various effects of drugs on the ear.

Action Potentials↗
PubMed2006

MicroRNA gene expression in the mouse inner ear.

MicroRNAs (miRNAs) are small non-coding RNAs that function through the RNA interference (RNAi) pathway and post-transcriptionally regulate gene expression in eukaryotic organisms. While miRNAs are known to affect cellular proliferation, differentiation, and morphological development, neither their expression nor roles in mammalian inner ear development have been characterized. We have investigated the extent of miRNA expression at various time points throughout maturation of the postnatal mouse inner ear by microarray analysis. Approximately one third of known miRNAs are detected in the inner ear, and their expression persists to adulthood. Expression of such miRNAs is validated by quantitative PCR and northern blot analysis. Further analysis by in situ hybridization demonstrates that certain miRNAs exhibit cell-specific expression patterns in the mouse inner ear. Notably, we demonstrate that miRNAs previously associated with mechanosensory cells in zebrafish are also expressed in hair cells of the auditory and vestibular endorgans. Our results demonstrate that miRNA expression is abundant in the mammalian inner ear and that certain miRNAs are evolutionarily associated with mechanosensory cell development and/or function. The data suggest that miRNAs contribute substantially to genetic programs intrinsic to development and function of the mammalian inner ear and that specific miRNAs might influence formation of sensory epithelia from the primitive otic neuroepithelium.

Animals↗
PubMed2004

Antibodies to inner ear antigens in Meniere's disease.

Meniere's disease (MD) is an idiopathic inner ear disorder characterized by fluctuating hearing loss, episodic vertigo and tinnitus. Its aetiology is unknown, although there is growing evidence that autoimmunity may be involved in its development. Using the Western blot immunoassay, we examined the reactivity to bovine inner ear antigens of sera from a series of MD patients who had previously been extensively studied for the presence of antibodies to collagens and membrane proteins. Reactivity to inner ear antigens of molecular weight 44 and 53 kD was found in 11/25 (44%) and 10/25 (40%) of the patients, respectively; both antigens were absent in the sera of healthy donors. It is still unclear whether the antibodies to 44 and 53 kD proteins play a role in the pathogenesis of MD or if they instead represent the result of inflammation and tissue destruction. Even if the latter is true, they may contribute to the perpetuation of the disease or play a role as a cofactor in association with other mechanisms.

Adult↗
PubMed2005

Gbx2 is required for the morphogenesis of the mouse inner ear: a downstream candidate of hindbrain signaling.

Gbx2 is a homeobox-containing transcription factor that is related to unplugged in Drosophila. In mice, Gbx2 and Otx2 negatively regulate each other to establish the mid-hindbrain boundary in the neural tube. Here, we show that Gbx2 is required for the development of the mouse inner ear. Absence of the endolymphatic duct and swelling of the membranous labyrinth are common features in Gbx2-/- inner ears. More severe mutant phenotypes include absence of the anterior and posterior semicircular canals, and a malformed saccule and cochlear duct. However, formation of the lateral semicircular canal and its ampulla is usually unaffected. These inner ear phenotypes are remarkably similar to those reported in kreisler mice, which have inner ear defects attributed to defects in the hindbrain. Based on gene expression analyses, we propose that activation of Gbx2 expression within the inner ear is an important pathway whereby signals from the hindbrain regulate inner ear development. In addition, our results suggest that Gbx2 normally promotes dorsal fates such as the endolymphatic duct and semicircular canals by positively regulating genes such as Wnt2b and Dlx5. However, Gbx2 promotes ventral fates such as the saccule and cochlear duct, possibly by restricting Otx2 expression.

Animals↗
PubMed2002

Cochlear implantation in children with inner ear malformations: report of two cases.

UNLABELLED: Cochlear implantation of congenitally deaf children with inner ear malformations is gaining special interest. Although the number of the reported cases is increasing, the decision for implantation needs thorough investigation. Preoperative evaluation, surgical approach and postoperative follow-up can be challenging. STUDY DESIGN: A retrospective analysis of two cases with inner ear malformations. PATIENTS: One patient was a 3-year-old-girl who had cochlear and cochleovestibular nerve aplasia on the left side and incomplete partition on the other side. The other patient was a 5-year-old-boy who had hypoplastic cochlea on both sides. Both of them also had vestibular anomalies. Cases were implanted by using multichannel cochlear implant. RESULTS: No complications were encountered. Both patients responded to acoustic stimuli, and their speech perception skills were improved. After 10 months of cochlear implant use, their results seem encouraging. CONCLUSION: Except cochlear or cochleovestibular nerve agenesis, inner ear malformations cannot be accepted as a contraindication for cochlear implantation. Although there can be difficulties during the surgery or in the postoperative period, patients with inner ear malformations can also benefit from cochlear implantation. It is essential that all possible complications and postoperative performance should be discussed with the parents.

Audiometry↗
PubMed1996

Mutations affecting development of the zebrafish inner ear and lateral line.

Mutations giving rise to anatomical defects in the inner ear have been isolated in a large scale screen for mutations causing visible abnormalities in the zebrafish embryo (Haffter, P., Granato, M., Brand, M. et al. (1996) Development 123, 1-36). 58 mutants have been classified as having a primary ear phenotype; these fall into several phenotypic classes, affecting presence or size of the otoliths, size and shape of the otic vesicle and formation of the semicircular canals, and define at least 20 complementation groups. Mutations in seven genes cause loss of one or both otoliths, but do not appear to affect development of other structures within the ear. Mutations in seven genes affect morphology and patterning of the inner ear epithelium, including formation of the semicircular canals and, in some, development of sensory patches (maculae and cristae). Within this class, dog-eared mutants show abnormal development of semicircular canals and lack cristae within the ear, while in van gogh, semicircular canals fail to form altogether, resulting in a tiny otic vesicle containing a single sensory patch. Both these mutants show defects in the expression of homeobox genes within the otic vesicle. In a further class of mutants, ear size is affected while patterning appears to be relatively normal; mutations in three genes cause expansion of the otic vesicle, while in little ears and microtic, the ear is abnormally small, but still contains all five sensory patches, as in the wild type. Many of the ear and otolith mutants show an expected behavioural phenotype: embryos fail to balance correctly, and may swim on their sides, upside down, or in circles. Several mutants with similar balance defects have also been isolated that have no obvious structural ear defect, but that may include mutants with vestibular dysfunction of the inner ear (Granato, M., van Eeden, F. J. M., Schach, U. et al. (1996) Development, 123, 399-413,). Mutations in 19 genes causing primary defects in other structures also show an ear defect. In particular, ear phenotypes are often found in conjunction with defects of neural crest derivatives (pigment cells and/or cartilaginous elements of the jaw). At least one mutant, dog-eared, shows defects in both the ear and another placodally derived sensory system, the lateral line, while hypersensitive mutants have additional trunk lateral line organs.

Animals↗
PubMed2006

Inner ear proteomics of mouse models for deafness, a discovery strategy.

Inner ear dysfunction is often associated with defective hair cells. Therefore, hair cells are the focus of study in many of the mouse mutants showing auditory and vestibular deficits. However, harvesting sufficient numbers of hair cells from the tiny bony mouse inner ear for proteomic analysis is challenging. New approaches that would take advantage of mouse mutants and avoid processing steps, such as decalcification or microdissetion, would be more suitable for proteomic analysis. Here, we propose a novel approach called SSUMM-Subtractive Strategy Using Mouse Mutants. SSUMM takes advantage of the differences between control and affected or mutant samples. We predict that SSUMM would be a useful method in proteomics, especially in those cases in which the investigator must work with small numbers of diverse cell types from a tiny organ. Here, we discuss the potential utility of SSUMM to unravel the protein expression profiles of hair cells using the Pou4f3 mouse mutant as an example. Pou4f3 mutant mice exhibit a total loss of inner and outer hair cells, but supporting cells remain relatively intact in the cochlea, thus providing an excellent model for identifying proteins and transcripts that are specific to the hair cell at all life stages. SSUMM would maximize the sensitivity of the analyses while obviating the need for tedious sessions of microdissection and collection of hair cells. By comparing the mutant to control ears at specific time points, it is possible to identify direct targets of a gene product of interest. Further, SSUMM could be used to identify and analyze inner ear development markers and other known genes/proteins that are coexpressed in the ear. In this short technical report, we also discuss protein-profiling approaches suitable for SSUMM and briefly discuss other approaches used in the field of proteomics.

Animals↗
PubMed1977

[Inner ear hearing loss following blunt head injury (author's transl)].

The pathologenesis of inner ear hearing loss after head injury is not uniform. Recent experimental and clinical findings in ophthalmology, neuropathology and neurosurgery indicate that there is not only a direct mechanical caused damage but as well an indirect injury of the inner ear secondary to disturbances of the cerebral blood supply. These cases representing about 30% of the patients are characterized by fluctuating hearing loss, which may increase of decrease even weeks or months after the incident. To assist inner ear microcirculation after head injury we therefore suggest to try an early treatment with medicaments increasing the cochlear blood flow, provided that the general conditions of the patients tolerate this.

Animals↗
PubMed1996

Myelin protein Po as a potential autoantigen in autoimmune inner ear disease.

We have previously shown that a 30,000 Mr protein extracted from guinea pig inner ear tissue is recognized by autoantibodies present in the serum of patients suffering from autoimmune inner ear disease. This protein was localized in the modiolus and in the organ of Corti. We have now identified this protein by a combination of microsequencing and matrix-assisted laser desorption ionization time-of-flight mass spectrometry of its tryptic peptides. A partial sequence of the protein was thereby determined. These data and 2-dimensional gel electrophoresis followed by immunoblotting experiments showed that the 30,000 Mr inner ear antigen is the major peripheral myelin protein Po. This suggests that protein Po may be an important autoantigen in autoimmune inner ear disease.

Amino Acid Sequence↗
PubMed2002

Localization of efferent neurotransmitters in the inner ear of the homozygous Bronx waltzer mutant mouse.

Naturally occurring mutant mice provide an excellent model for the study of genetic malformations of the inner ear. Mice homozygous for the Bronx waltzer (bv/bv) mutation are severely hearing impaired or deaf and exhibit a 'waltzing' gait. Functional aspects of cochlear and vestibular efferents in the bv/bv mutant mouse are not well known. The present study was designed to evaluate several candidates of efferent neurotransmitters or neuromodulators including choline acetyltransferase (ChAT), gamma-aminobutyric acid (GABA), and calcitonin gene-related peptide (CGRP) in the inner ear of the bv/bv mutant mouse. Ultrastructural investigations at both light and electron microscopic level were performed. Ultrastructural morphologic evaluations of the cochlea and the vestibular end-organs were also undertaken. It is demonstrated that ChAT, GABA and CGRP immunoreactivities are present in the cochlea and in vestibular end-organs of bv/bv mutant mice. In the organ of Corti, immunoreactivity of ChAT, GABA and CGRP is confined to the inner spiral fibers, tunnel-crossing fibers, and the vesiculated nerve endings synapsing with outer hair cells. Interestingly, immunoreactivity was detectable even where inner hair cells appeared missing. Results also revealed malformations of the outer hair cells with synaptic contacts to efferent nerve endings consistently intact. In the neurosensory epithelia of the vestibular end-organs, the presence of ChAT, GABA, and CGRP immunoreactivity was localized at the vestibular efferents, with the exception of the macula of saccule. In one 8-month-old macula of utricle where the depletion of hair cells appeared highest, ChAT immunostaining was still discernible. Ultrastructural investigation demonstrated that vesiculated efferent nerve endings make synaptic contact with the outer hair cells in the organ of Corti and with type II hair cells in the vestibular end-organs. The present study provides further support that the efferent system in the bv/bv mutant inner ear is morphologically as well as functionally mature. These findings also demonstrate that if and when the onset of efferent degeneration in the bv/bv mutant inner ear occurs, it transpires subsequent to pathological conditions in the hair cells. The present findings give further indication that the efferent systems of the bv/bv mutant inner ear are independent of the afferent systems in many aspects including development, maturation as well as degeneration.

Animals↗
PubMed2001

Developmental expression of monocarboxylate transporter in the gerbil inner ear.

The expression of H+-monocarboxylate cotransporters (MCTs) that facilitate cell uptake of lactate, pyruvate and other monocarboxylates was investigated in the adult and postnatally developing gerbil inner ear. In the mature cochlea, immunoreactive MCT1 was present in marginal cells of the stria vascularis and in type II, suprastrial and limbal fibrocytes. In the adult vestibular system, dark cells and a subpopulation of fibrocytes immediately underlying maculae and cristae stained strongly for MCT1. Satellite cells surrounding mature spiral and vestibular ganglia neurons also expressed MCT1. MCT1 immunoreactivity was present at birth in marginal and dark cells, at 8 days after birth in fibrocytes and at 12 days after birth in satellite cells, and coincided precisely with the developmental expression of Na,K-ATPase in these sites. The coexpression of MCT1 and Na,K-ATPase in these cell types points to MCT1 as an important source of energy to drive inner ear Na,K-ATPase activity. In the adult inner ear, MCT2 was detectable only in tectal cells of the cochlea and supporting cells of the crista ampullaris. Immunostaining was first observed at 16 days after birth in tectal and at 20 days after birth in supporting cells, and at the same time immunoreactive aquaporin 4 appeared in these cells. The coexpression of MCT2 and aquaporin 4 suggests a possible role for MCT2 in regulating transcellular water movement. Because MCT2 facilitates the transport of acidic intermediates, its biological significance also could relate to modulation of cell pH and volume. Maintenance of the inner ear's unique ion and fluid gradients is essential to normal hearing and balance and requires the expenditure of large amounts of energy. The cellular distribution of MCT1 and MCT2 points to their participation in generating these electrochemical gradients and their potential involvement in sensory deficits associated with various inner ear disorders.

Aging↗
PubMed1989

[Potentiation of inner ear damage following electron beam irradiation with CDDP administration].

The study was designed to examine the combined ototoxic effect of CDDP (Cisplatin, Cis-diammine dichloroplatinum) and electron beam irradiation, using guinea pigs. One group received physiological saline solution of 4 ml/kg/day, and another group received CDDP of 2 mg/kg/day for five days. And following the injection of saline or CDDP, the electron beam of 14Gy/day was applied to the both groups to the right ear for five days. Animals were sacrificed after 21 days, and temporal bones of these animals were removed for the inner ear histopathology. Temporal bones were classified into four groups (control, electron beam irradiation, CDDP administration, and combined administration group), and the inner ears were observed by the surface preparation technique with a phase contrast microscope, and by scanning and transmission electron microscopy, and by temporal bone study of serial sectioned slides. The main pathologic findings of the inner ear are as follows: Electron beam irradiation group showed no hair cell damage. CDDP group induced slight damage to the outer hair cells. Combined administration group (CDDP + electron beam irradiation) showed severe outer hair cell damage. Stria vascularis was degenerated moderately in the combined administration group and slightly in some animals of electron beam irradiation group. And Reissner's membrane and Hensen's cells, were damaged in the basal turn of cochlea of the combined administration group. All other cochlear structures (spiral ganglion, spiral lamina, basilar membrane, spiral prominence, tectorial membrane, blood vessels of the cochlea) and vestibular organs were lack of significant changes in all groups by a light microscopic observation. This study was clarified that combined administration of CDDP and electron beam irradiation showed severe ototoxic potentiation. Therefore, it is important that we must pay attention to the inner ear damage caused by combined therapy of CDDP and electron beam irradiation involving inner ear for the head and neck tumor.

Animals↗
PubMed2006

Bone marrow mesenchymal stem cells are progenitors in vitro for inner ear hair cells.

Stem cells have been demonstrated in the inner ear but they do not spontaneously divide to replace damaged sensory cells. Mesenchymal stem cells (MSC) from bone marrow have been reported to differentiate into multiple lineages including neurons, and we therefore asked whether MSCs could generate sensory cells. Overexpression of the prosensory transcription factor, Math1, in sensory epithelial precursor cells induced expression of myosin VIIa, espin, Brn3c, p27Kip, and jagged2, indicating differentiation to inner ear sensory cells. Some of the cells displayed F-actin positive protrusions in the morphology characteristic of hair cell stereociliary bundles. Hair cell markers were also induced by culture of mouse MSC-derived cells in contact with embryonic chick inner ear cells, and this induction was not due to a cell fusion event, because the chick hair cells could be identified with a chick-specific antibody and chick and mouse antigens were never found in the same cell.

Actins↗
PubMed1996

Type II collagen-induced autoimmune ear disease in mice: a preliminary report on an epitope of the type II collagen molecule that induced inner ear lesions.

To identify the epitope on the type II collagen molecule that induced autoimmune ear disease, electrophysiological and histological studies were carried out in DBA/1J mice immunized with native chick type II collagen (Clln) and cyanogen bromide (CNBr) peptide 1I (CB-I1 peptide) that was cleaved from chicken type II collagen with CNBr digestion. Four months after immunization, three of six Clln-immunized mice and five of six CB-I1 peptide-immunized mice developed moderate hearing loss. No control animals showed hearing loss. The pattern of hearing loss was characteristic of progressive deafness. Furthermore, the immunized mice showed temporal lesions involving atrophy of the Corti organ and degeneration of the spiral ganglion, in proportion to the level of the hearing loss. Because similar inner ear lesions were induced by immunization with Clln and CB-I1 peptide, CB-I1 peptide contains at least one epitope that induces autoimmune inner ear disease in collagen II-induced disease on the chick type II collagen molecule involved in pathogenesis of autoimmune ear disease. CB-I1 peptides were concluded to contain the epitope that induces autoimmune inner ear disease in collagen IIn-induced disease.

Animals↗
PubMed2002

Pharmacologic treatment of inner ear: from basic science to the patient.

Most of the deafness are of sensorineural origin and are characterized by a loss of hair cells and of spiral ganglion neurons. At the present time, hearing aids are the only treatment. However, in some diseases of the inner ear, pharmacological treatment have been proposed and used successfully. In this paper, we will review some basic science aspects of the biology of the neurosensory structures of the inner ear, in particular of the auditory neurons, that lead to the rationale of some treatments for the inner ear diseases. Developmental studies, neuronal cell culture experiments, and analyses of gene knockout animals reveal a number of growth factors which are important for the rescue and repair of injured auditory neurons in the inner ear. These factors rescue the injured auditory neurons in vivo. Furthermore, perfusion of antioxydant to the cochlea prevented the hearing loss induced by cisplatin. These in vitro and in vivo experiments demonstrate that it is possible to manipulate the neurosensory structures of the inner ear and provide an effective treatment to prevent the degeneration of the neurons. The molecules or drugs can be administered locally to the inner ear through a direct perilymphatic perfusion or through the round window membrane. As an example, we will discuss the treatment of patients suffering from idiopathic sensorineural hearing loss which can be treated successfully by a perfusion through the round window membrane, improving their hearing threshold and their speech discrimination.

Animals↗
PubMed1999

Use of a new device, the MicroWick, to deliver medication to the inner ear.

A new procedure for delivering medication directly to the inner ear has been developed. This delivery system, called the MicroWick, involves the use of a small wick that is inserted through a tympanic membrane vent tube into the round window niche. Once the wick has been inserted, the patient can self-administer eardrops into the ear canal, where they are absorbed by the wick and transported to the round window membrane and to the inner ear fluids. Inserting the wick is a minor procedure that is performed in the office. This paper describes the indications for and use of the MicroWick.

Anti-Bacterial Agents↗
PubMed2005

Identification of cis-element regulating expression of the mouse Fgf10 gene during inner ear development.

Fibroblast growth factor (FGF) signaling is crucial for the induction and growth of the ear, a sensory organ that involves intimate tissue interactions. Here, we report the abnormality of Fgf10 null ear and the identification of a cis-regulatory element directing otic expression of Fgf10. In Fgf10 null inner ears, we found that the initial development of semicircular, vestibular, and cochlear divisions is roughly normal, after which there are abnormalities of semicircular canal/cristae and vestibular development. The mutant semicircular disks remain without canal formation by the perinatal stage. To elucidate regulation of the Fgf10 expression during inner ear development, we isolated a 6.6-kb fragment of its 5'-upstream region and examined its transcriptional activity with transgenic mice, using a lacZ-reporter system. From comparison of the mouse sequences of the 6.6-kb fragment with corresponding sequences of the human and chicken Fgf10, we identified a 0.4-kb enhancer sequence that drives Fgf10 expression in the developing inner ear. The enhancer sequences have motifs for many homeodomain-containing proteins (e.g., Prx, Hox, Nkx), in addition to POU-domain factors (e.g., Brn3), zinc-finger transcription factors (e.g., GATA-binding factors), TCF/LEF-1, and a SMAD-interacting protein. Thus, FGF10 signaling is dispensable for specification of otic compartment identity but is required for hollowing the semicircular disk. Furthermore, the analysis of a putative inner ear enhancer of Fgf10 has disclosed a complicated regulation of Fgf10 during inner ear development by numerous transcription factors and signaling pathways.

Animals↗