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PubMed2004

[Apoptosis in the immune response of inner ear].

OBJECTIVE: To investigate whether apoptosis is one of the mechanism in the immune response of inner ear,and to detect the expression of Fas, FasL, Bcl-2 and Bax in the inner ears. METHODS: Sixteen healthy, female guinea pigs were employed in the experiment. Sensitized systematically with keyhole limpet hemocyanin (KLH), the KLH-immunized animals were inoculated with the same antigen, and the control animals were injected PBS through cochlea basal turn. The animals were sacrificed at 7 day after inner ear vaccination. Transmission electron microscopy was used to detect inner ear apoptotic cells, and paraffin sections of cochlea from animals were stained using a terminal-deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) assay to identify inner ear cells undergoing apoptosis. Immunohistochemistry method was used to detect the expression of Fas, FasL, Bcl-2 and Bax in the inner ears. RESULTS: The observation of electron microscopy had shown the features characteristic of apoptotic cells in the KLH-immunized inner ears but not in the control inner ears. TUNEL-positive cells were found in the KLH-immunized inner ears but not in the control inner ears. The positive cells were the hair cells in Corti's organ, and the marginal cells in the stria vascularis and the neurons in the spiral ganglion. Moreover under morphological analysis by light microscope, these cells had the features characteristic of apoptosis. High expression of Fas and FasL could be detected in Corti's organ, the stria vascularis, the spiral ligament and the neurons of the spiral ganglion in the KLH-immunized inner ears. A low expression of Fas could be detected in the stria vascularis and the neurons of the spiral ganglion in the control inner ears, but no cells staining positive for FasL were found in the control inner ears. No cells staining positive for Bcl-2 were found in the KLH-immunized animals but moderate expression of Bcl-2 could be detected in Corti's organ, the lateral wall and the neurons of the spiral ganglion in the control inner ears. High expression of Bax could be detected in Corti's organ, the lateral wall and the neurons of the spiral ganglion in the KLH-immunized inner ears. A low expression of Bax could be detected in the neurons of the spiral ganglion and no cells staining positive for Bax were found in Corti's organ, the lateral wall in the control inner ears. CONCLUSIONS: These findings suggest apoptosis is involved in the pathogenesis of the immune response of inner ear and Fas- FasL pathway is one of important signal transportation of the course and Bcl-2 and Bax have a critical role in the regulation of apoptotic cell death induced by the immune response of inner ear.

Animals↗
PubMed1993

Hair-cell regeneration in organ cultures of the postnatal chicken inner ear.

The sensory epithelium of the avian inner ear retains into adulthood progenitor cells for inner-ear hair cells and other cell types in the epithelium. Hair cells are produced normally on an ongoing basis in the vestibular sensory epithelium, and hair-cell production is increased after insult in both auditory and vestibular sensory epithelia. The details of postnatal hair-cell production are not understood. In particular, molecular factors involved in the initiation and regulation of hair-cell genesis and differentiation are not known. Studies of this phenomena have been hampered by the lack of cell culture models. An organ culture system was developed which encourages generation and differentiation of hair cells in mature inner-ear sensory epithelia. Continuous labeling with tritiated thymidine showed genesis of both supporting cells and hair cells in normal vestibular epithelia grown in culture, and an increase in hair-cell and supporting-cell proliferation in damaged sensory epithelia grown in culture as compared to undamaged controls. This demonstrates, in vitro, both the division and differentiation of hair-cell progenitor cells in normal vestibular epithelia, and the maintenance of the hair-cell regeneration process in damaged inner-ear epithelia. This culture system should be useful for studies of hair-cell genesis and differentiation as well as studies of hair-cell and supporting-cell functioning in general.

Animals↗
PubMedDate not supplied

Characteristics of sensorineural hearing loss in children with inner ear anomalies.

PURPOSE: To determine whether hearing loss in children with inner ear anomalies has some distinctive characteristics when compared to children with hearing loss but without inner ear anomalies. METHODS: Temporal bone computed tomography scans of 69 patients with sensorineural hearing loss were examined for inner ear abnormalities of which 17 were identified. The medical histories of these patients were reviewed for the characteristics of their hearing loss, including initial presentation, natural history, and nature of loss, as well as the family history of hearing loss and risk factors for hearing loss. These were compared to age-matched controls with hearing loss but without inner ear anomalies. RESULTS: Seventeen patients had inner ear anomalies. Records of 14 of these patients were compared to patients without inner ear anomalies. Regarding age of onset, 71.4% of patients with anomalies had onset of their hearing loss at less than 2 years old vs 78.6% without anomalies. Regarding unilateral vs bilateral, 42.9% of patients with anomalies were unilateral vs 28.6% of patients without anomalies. For patients with anomalies, 85.7% were stable and 14.3% were progressive; without anomalies, 71.4% were stable, 21.4% were progressive, and 7.1% were fluctuating. Regarding family history, only 14.3% of patients without anomalies had a positive family history vs 56% of patients with anomalies. CONCLUSIONS: Children with inner ear anomalies and sensorineural hearing loss have an increased incidence of unilateral hearing loss and stable hearing loss as compared to controls with sensorineural hearing loss without inner ear anomalies. In addition, children with inner ear anomalies and sensorineural hearing loss are less likely to have a family history of hearing loss.

Age Distribution↗
PubMed1995

Use of the teleost saccule to identify genes involved in inner ear function.

The vertebrate inner ear sensory epithelia contain different types of hair cells and supporting cells. The teleost saccule is anatomically similar to the mammalian saccule and is primarily involved in the detection of translational acceleration and orientation with respect to gravity. To facilitate molecular studies of the teleost saccule cDNA libraries were constructed from microdissected Lepomis macrochirus (bluegill sunfish) saccular maculae. To our knowledge, this is the first report of cDNA libraries constructed from the saccule. In one instance, a non-polymerase chain reaction-based method of amplifying a mRNA population from limited amounts of starting tissue was employed that allowed construction of cDNA libraries from nanogram amounts of tissue mRNA. Conventional cDNA libraries were constructed from the sunfish saccular maculae as well. These cDNA libraries enriched in hair cell and supporting cell transcripts should facilitate molecular biological studies of inner ear sensory epithelia. As an example of their utility, efforts to identify tyrosine kinases expressed in the saccular endorgan using low-stringency hybridization screening of these cDNA libraries and the partial sequence of a cDNA found to encode an erbB-2-related tyrosine kinase are also reported.

Amino Acid Sequence↗
PubMed2004

Biological therapy for the inner ear.

Biological therapy for the inner ear has the potential to revolutionise the treatment of sensorineural hearing loss, the most common form of deafness. Progress in the molecular understanding of hearing and hearing loss, combined with advances in the fields of both gene and cellular therapy for the inner ear, is providing a robust foundation from which clinical translation is plausible. Potential areas of interest in gene therapy and its preclinical application to deafness are reviewed, and experimental progress that has occurred in cellular therapy for the inner ear is examined.

Animals↗
PubMed2003

[Immunohistochemical study for monoamine neurons in the brain of unilateral inner ear impaired rats].

Patients with inner ear impairment have complaints of vertigo and also occasionally depression. The present study was undertaken in order to evaluate changes in monoamines which have reportedly been closely related to depression, using cisplatin-induced unilateral inner-ear impaired rats. A dose of 0.5 mg/kg of cisplatin was injected into the right tympanic cavity under pentobarbital Na+ anesthesia. One or two weeks later, animals were fixed with paraformaldehyde, and thereafter immunohistochemical stainings for monoamine-containing cells in the brain were carried out. To visualize 5-hydroxytryptamine (5-HT), noradrenaline (NA) and dopamine (DA) neurons, we used mouse antibodies against 5-HT, NA, and DA syntheses, i.e., tryptophan hydroxylase (TRH), tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH). The number of TRH immunoreactive neurons significantly decreased in the lateral dorsal raphe nucleus of the ipsilateral side when compared with the contralateral side. The number of DA neurons, which were immunoreactive to TH, but not to DBH, significantly decreased in the hypothalamus of the ipsilateral side. The number of NA neurons which were immunoreactive to both TH and DBH significantly decreased in the locus coeruleus and ventral lateral pons of the ipsilateral side. An additional control study with saline-injected rats showed a lack of differences in monoamine syntheses between the injected and contralateral sides, the expressions of the synthesis on both sides being similar to that obtained in the contralateral side in cisplatin-injected rats. These results indicated the decreases in monoamine syntheses at the ipsilateral side only in the cisplatin-administered rats. We conclude that inner ear impairment may diminish the ipsilateral amount of monoamines in the brain but not the cotralateral, possibly inducing a vestibular compensation such as an upregulation of monoamine receptors.

Animals↗
PubMed2002

In silico analyses of mouse inner-ear transcripts.

The development and function of the inner ear is complex requiring the correct and coordinated expression of many genes. The recent progress in the analyses of the human and other genomes has provided tools for identification of genes involved in hearing. As more and more nucleotide sequence information accumulates, experimental methods of molecular biology are rapidly being supplemented, and partially supplanted, by computational methods. In this study we present comprehensive in silico analyses of a cDNA library representing almost 1600 transcripts isolated from mouse inner ear. By mining the public databases we were able to rapidly and efficiently identify numerous transcripts likely to have a specific role in the auditory or vestibular function of the inner ear. Analyses revealed about 600 known genes and almost 100 inner-ear specific transcripts. Almost 50 of these are candidate genes for hearing impairment based on their chromosomal localization and inner-ear expression pattern. We describe a powerful approach to identify novel genes associated with hearing and vestibular function, further increasing our understanding of the molecular biology of the inner ear.

Animals↗
PubMed1997

Autoimmune inner ear disease--a real entity?

Involvement of autoimmune mechanisms in sudden-onset, rapidly progressive, bilateral inner ear disease is supported by the following evidence: (1) the inner ear contains immune cells and mediators (immunoglobulins); (2) animal models demonstrate inner ear damage after immunization with inner ear tissue; (3) experimental autoimmune inner ear disease appears to be transferable with sensitized T cells; (4) human SNHL can occur in the context of systemic immunologic disease; (5) SNHL can be improved by immunosuppressive therapy; and (6) patients with SNHL demonstrate elevated immune responses to inner ear proteins/tissue preparations. There are also several reasons, however, why the above inner ear disease cannot be termed "autoimmune": (1) in experimental models, inner ear damage may be produced during an in situ immune response to an irrelevant antigen; (2) histopathology is not yet extensive enough to confirm the role of immune cells and mediators in human disease; (3) immune reactivity to an organ-specific antigen associated with the inner ear has not yet been identified. At this time, therefore, clinical inner ear disease with evidence of immunologic involvement is termed "immune-mediated" rather than "autoimmune." IMIED is likely to represent a heterogeneous group of diseases with multifactorial causes but a common endpoint. Diagnosis is made primarily by clinical profile in association with laboratory testing to rule out neoplasia or infection. Investigational laboratory immunoassays for antibodies to inner ear proteins or hsp 70 appear to have promise for diagnosis or predicting clinical response to immunosuppressive treatment. Sensitivity and specificity of such assays have not yet been established.

Autoimmune Diseases↗
PubMed1992

[Experimental autoimmune lesions of the inner ear].

This paper presents the autoimmune lesions of the inner ear by using isologous inner ear antigen (IEAg) on the guinea pigs. The purposes of this study were to determine whether the inner ear is an immune response organ and what is the sequelae of the immune processes both on physiological and morphological changes in the inner ear. Animals were systemically sensitized with IEAg in complete Freund's adjuvant and boothed with IEAg in incomplete Freund's adjuvant three times in every 3-4 weeks and then allowed to survive 4-6 weeks. For the ABR measurement, 8 of 28 ears (28.6%) in the experimental group showed threshold enhancement greater than or equal to 10dB before the animal sacrifice and the mean threshold shift of the ABR 8 weeks post immunization and before sacrifice revealed significant difference. Histological specimens were processed for both light and electron microscopic study. In the LM study, it showed endolymphatic hydrops, local thickening of the Reissener's membrane, and spiral ganglion cells lost. In the SEM, disturbance and loss of the cilia of the outer hair cells of the cochlea and the type I and II sensory cells in the crista ampularis can be seen. Also, some otoconia showed numerous malformation.

Animals↗
PubMed1998

Distinct expression patterns of notch family receptors and ligands during development of the mammalian inner ear.

The cochlea and vestibular structures of the inner ear labyrinth develop from the otic capsule via step-wise regional and cell fate specification. Each inner ear structure contains a sensory epithelium, composed of hair cells, the mechanosensory transducers, and supporting cells. We examined the spatio-temporal expression of genes in the Notch signaling pathway, Notch receptors (Notch1-4) and two ligands, Jagged1 and Delta1, in the developing mammalian inner ear. Our results show that Notch1 and Jagged1 are first expressed in the otic vesicle, likely involved in differentiation of the VIIIth nerve ganglion neurons, and subsequently within the inner ear sensory epithelia, temporally coincident with initial hair cell differentiation. Notch1 expression is specific to hair cells and Jagged1 to supporting cells. Their expression persists into adult. Notch2, Notch3, Notch4, and Delta1 are excluded from the inner ear epithelia. These data support the hypothesis that Notch signaling is involved in hair cell differentiation during inner ear morphogenesis.

Animals↗
PubMed2000

Development. Hear, hear, for the inner ear.

Although the development of the inner ear has been a favorite subject for biologists to study, it is not yet clear exactly which molecules are involved in the induction of the otic placode, the plug of embryonic ectoderm that will become the inner ear. In his Perspective, Graham takes us on an inner ear odyssey, explaining how the signaling molecules FGF-19 and Wnt-8c cooperate to induce formation of the otic placode (Ladher et al.).

Animals↗
PubMed1992

Round window membrane rupture and inner ear damage due to barotrauma.

We investigated inner ear barotrauma in humans and in guinea pigs. The shapes of audiograms in patients with inner ear barotrauma were varied, such as high-tone hearing loss, profound loss, low-tone hearing loss, dip type, etc. In inner ear barotrauma in guinea pigs, damage to the organ of Corti was observed in various parts of the cochlear turns in varying severity. Some animals showed rupture of the round window membrane and/or reduction of endocochlear potential following the barotrauma but the rupture healed and EP recovered spontaneously within one week. We consider that irreversible hearing loss in patients with inner ear barotrauma depends on the extent of damage to the organ of Corti.

Animals↗
PubMed2003

[Clinical review of inner ear malformation].

We had 126 patients with inner ear malformation diagnosed with temporal bone computed tomography (CT) scans at Azabu Triology Hospital between 1996 and 2002. We classified cases of inner ear malformation according to Jackler et al. The incidence of inner ear malformation in our series was as follows; 1. Labyrynthine anomalies 61% (isolated lateral semicircular canal dysplasia 56%, compound semicircular canal dysplasia 4%, semicircular canal aplasia 1%), 2. Cochlear anomalies 24%, 3. Enlargement of the vestibular aqueduct 12%, 4. Narrow internal auditory canal 2%, 5. Complete labyrinthine aplasia 1%, 6. Enlargement of the cochlear aqueduct 0%. The most frequent anomaly was isolated lateral semicircular canal dysplasia. We did not detect any significant clinical features in this anomaly. There were 2 patients with cochlear anomalies who had past histories of meningitis. Some patients with enlargement of the vestibular aqueduct had frequent attacks of fluctuating hearing. Clinically it is important to detect patients with inner ear malformation such as cochlear anomalies and enlargement of the vestibular aqueduct usually accompanied by congenital sensorineural hearing loss. For patients with congenital sensorineural hearing loss, we recommend temporal bone CT scan.

Adolescent↗
PubMed1998

[Expression of intercellular adhesion molecule-1 in immune response of the inner ear].

OBJECTIVE: To understand the role of intercellular adhesion molecule-1(ICAM-1) in the immune response of the inner ear. METHODS: Inner ear immune response was induced in rats by inoculation of key-hole limpet hemocyanine(KLH) into the scala tympani of animals who had been systemically sensitized. Then the expression of ICAM-1 in the inner ear was examined by immunohistochemistry. RESULTS: ICAM-1 was found in the epithelium of the spiral modiolar vein (SMV) with its collecting venules (CV) as early as 6 hours postchallenge. Expression of ICAM-1 was observed on the epithelium of the endolymphatic sac(ES) and perisaccular region at 12 hours. The intensity of ICAM-1 staining reached a maximum by 24 or 48 hours in these sites of the inner ear. By day 28, most specimens were devoid of significant staining for ICAM-1. CONCLUSION: The study elucidates the important role of adhesion molecules in extravasation of inflammatory cells from the systemic circulation during an inner ear immune response. It also shows that cytokines controlling expression of adhesion molecules may be released by cells located outside of ES besides those cells in the ES.

Adjuvants, Immunologic↗
PubMed2006

Tissue-specific roles of Tbx1 in the development of the outer, middle and inner ear, defective in 22q11DS patients.

Most 22q11.2 deletion syndrome (22q11DS) patients have middle and outer ear anomalies, whereas some have inner ear malformations. Tbx1, a gene hemizygously deleted in 22q11DS patients and required for ear development, is expressed in multiple tissues during embryogenesis. To determine the role of Tbx1 in the first pharyngeal pouch (PPI) in forming outer and middle ears, we tissue-specifically inactivated the gene using Foxg1-Cre. In the conditional mutants, PPI failed to outgrow, preventing the middle ear bone condensations from forming. Tbx1 was also inactivated in the otic vesicle (OV), resulting in the failure of inner ear sensory organ formation, and in duplication of the cochleovestibular ganglion (CVG). Consistent with the anatomical defects, the sensory genes, Otx1 and Bmp4 were downregulated, whereas the CVG genes, Fgf3 and NeuroD, were upregulated. To delineate Tbx1 cell-autonomous roles, a more selective ablation, exclusively in the OV, was performed using Pax2-Cre. In contrast to the Foxg1-Cre mutants, Pax2-Cre conditional mutant mice survived to adulthood and had normal outer and middle ears but had the same inner ear defects as the Tbx1 null mice, with the same gene expression changes. These results demonstrate that Tbx1 has non-cell autonomous roles in PPI in the formation of outer and middle ears and cell-autonomous roles in the OV. Periotic mesenchymal markers, Prx2 and Brn4 were normal in both conditional mutants, whereas they were diminished in Tbx1-/- embryos. Thus, Tbx1 in the surrounding mesenchyme in both sets of conditional mutants cannot suppress the defects in the OV that occur in the null mutants.

Animals↗
PubMed2006

Cadherin-2 participates in the morphogenesis of the zebrafish inner ear.

Molecular mechanisms that control inner ear morphogenesis from the placode to the three-dimensional functional organ are not well understood. We hypothesize that cell-cell adhesion, mediated by cadherin molecules, contributes significantly to various stages of inner ear formation. Cadherin-2 (Cdh2) function during otic vesicle morphogenesis was investigated by examining morpholino antisense oligonucleotide knockdown and glass onion (glo) (Cdh2 mutant) zebrafish embryos. Placode formation, vesicle cavitation and specification occurred normally, but morphogenesis of the otic vesicle was affected by Cdh2 deficiency: semicircular canals were reduced or absent. Phalloidin staining of the hair cell stereocillia demonstrated that cadherin-2 (cdh2) loss-of-function did not affect hair cell number, but acetylated tubulin labeling showed that hair cell kinocilia were shorter and irregularly shaped. Statoacoustic ganglion size was significantly reduced, which suggested that neuron differentiation or maturation was affected. Furthermore, cdh2 loss-of-function did not cause a general developmental delay, since differentiation of other tissues, including eye, proceeded normally. These findings demonstrate that Cdh2 selectively affects epithelial morphogenetic cell movements, particularly semicircular canal formation, during normal ear mophogenesis.

Animals↗
PubMed2004

DAN directs endolymphatic sac and duct outgrowth in the avian inner ear.

Bone morphogenetic proteins (BMPs) are expressed in the developing vertebrate inner ear and participate in inner ear axial patterning and the development of its sensory epithelium. BMP antagonists, such as noggin, chordin, gremlin, cerberus, and DAN (differential screening-selected gene aberrative in neuroblastoma) inhibit BMP activity and establish morphogenetic gradients during the patterning of many developing tissues and organs. In this study, the role of the BMP antagonist DAN in inner ear development was investigated. DAN-expressing cell pellets were implanted into the otocyst and the periotic mesenchyme to determine the effects of exogenous DAN on otic development. Similar to the effects on the inner ear seen after exposure of otocysts to the BMP4 antagonist noggin, semicircular canals were truncated or eliminated based upon the site of pellet implantation. Unique to the DAN implantations, however, were effects on the developing endolymphatic duct and sac. In DAN-treated inner ears, endolymphatic ducts and sacs were merged with the crus or grew into the superior semicircular canal. Both the canal and endolymphatic duct and sac effects were rescued by joint implantation of BMP4-expressing cells. Electroporation of DAN antisense morpholinos into the epithelium of stage 15-17 otocysts, blocking DAN protein synthesis, resulted in enlarged endolymphatic ducts and sacs as well as smaller semicircular canals in some cases. Taken together, these data suggest a role for DAN both in helping to regulate BMP activity spatially and temporally and in patterning and partitioning of the medial otic tissue between the endolymphatic duct/sac and medially derived inner ear structures.

Animals↗
PubMed1984

Inner ear fluids dynamics and endolymphatic hydrops.

The inner ear possesses remarkably stable homeostatic mechanisms for the maintenance of the functional integrity of the inner ear end-organs. The inner ear fluid maintains its homeostasis by a variety of subtle regulatory mechanisms, both locally and systemically. Any disturbance in one of these mechanisms can induce the disruption of homeostasis expressed by ionic, osmotic, or metabolic imbalance between the compartments. This can be manifested as membrane displacement or abnormal functions of the inner ear, depending on the degree of the disturbance. Further studies are necessary to clarify these regulatory mechanisms of homeostasis and those conditions which alter homeostasis which can result in the abnormal functions. Further research along this line is essential in order to understand the etiology of endolymphatic hydrops and also to establish guidelines for possible normalization of this pathological status.

Endolymph↗