Canalostomy As a Surgical Approach to Local Drug Delivery into the Inner Ears of Adult and Neonatal Mice

Local delivery of therapeutic drugs into the inner ear is a promising therapy for inner ear diseases. Injection through semicircular canals (canalostomy) ...

Capital Medical University

To evaluate the transduction efficiency of a recombinant adenovirus carrying the gene for green fluorescent protein (Ad-GFP) into the primary cultures of fetal neural stem cells (NSCs) by the expression of GFP.

Gene transfer into primary cultures of fetal neural stem cells by a recombinant adenovirus carrying the gene for green fluorescent protein.

The mammalian vestibular epithelium has a limited capacity for spontaneous hair cell regeneration. The mechanism underlying the regeneration is not well understood. Because the Notch signaling pathway mediates the formation of the sensory epithelial mosaic patterning during ear development, it may also play a role in hair cell regeneration in the mature mammalian vestibular epithelium after a lesion. To investigate the process of spontaneous regeneration in the vestibular epithelium vis-à-vis changes in Notch signaling, we induced a unilateral lesion by infusing streptomycin into the mouse posterior semicircular canal, and examined Notch signaling molecules and their mRNA expression levels by immunohistochemistry and quantitative real-time polymerase chain reaction (qRTPCR), respectively. We detected Jagged1 in supporting cells in both normal and lesioned utricles. Atoh1, a marker for early developing hair cells, was absent in the intact mature tissue, but re-appeared after the lesion. Many cells were either positive for both Atoh1 and myosin VIIa, or for one of them. qRTPCR data showed a post trauma decrease of Hes5 and an increase in Atoh1. Atoh1 up-regulation may either be a result of Hes5 down-regulation or mediated by another signaling pathway.

Notch signaling and Atoh1 expression during hair cell regeneration in the mouse utricle.

Vesicular glutamate transporter 3 (VGLUT3) plays an important role in hearing, and VGLUT3 knockout mice are deaf. However, the mechanisms whereby VGLUT3 exerts its effects in the cochlea are not well established. Elucidating the developmental and aging dynamics of VGLUT3 localization and expression in the cochlea would aid a functional understanding of auditory glutamatergic transmission. In this study, we characterized the expression of VGLUT3 in rat auditory epithelium and spiral ganglion cells (SGCs) during postnatal development and with age using immunohistochemistry and quantitative real-time reverse transcription polymerase chain reaction (RT-PCR). We observed VGLUT3 expression in cochlea inner hair cells (IHCs) and SGCs as early as postnatally, and its expression increased gradually with maturity. However, the expression of VGLUT3 in the IHCs decreased in the aging rats compared to postnatal day 60 (P60), and VGLUT3 was still expressed in the remaining SGCs in the aging rats. VGLUT3-immunopositive punctate structures were only found in the cytoplasm of SGCs, not IHCs, at P7, or later. Variation in VGLUT3 mRNA expression evaluated by quantitative real time RT-PCR was consistent with the immunohistochemical data except for no statistical difference between P60 and aging rats in the whole cochlea level. Our data suggest that VGLUT3 likely has developmental and physiological roles in the rat cochlea during postnatal development as well as later in life. VGLUT3 may have additional unknown roles in SGCs besides glutamate transport.

Temporospatial expression and cellular localization of VGLUT3 in the rat cochlea.

To evaluate the value of temporal bone dual phase contrast enhancement computed tomography (DPCT) in diagnosing the causes of pulsatile tinnitus (PT).

[Value of temporal bone dual phase contrast enhancement computed tomography in diagnosing causes of pulsatile tinnitus].

Treatment of pulsatile tinnitus associated with multiple factors.

Tumor necrosis factor (TNF)-α is a cytokine involved in acute inflammatory phase reactions, and is the primary upstream mediator in the cochlear inflammatory response. Treatment of the organ of Corti with TNF-α can induce hair cell damage. However, the resulting morphological changes have not been systematically examined. In the present study, cochlear organotypic cultures from neonatal mice were treated with various concentrations and durations of TNF-α to induce inflammatory responses. Confocal microscopy was used to evaluate the condition of hair cells and supporting cells following immunohistochemical staining. In addition, the ultrastructure of the stereocilia bundle, hair cells, and supporting cells were examined by scanning and transmission electron microscopy. TNF-α treatment resulted in a fusion and loss of stereocilia bundles in hair cells, swelling of mitochondria, and vacuolation and degranulation of the endoplasmic reticulum. Disruption of tight junctions between hair cells and supporting cells was also observed at high concentrations. Hair cell loss was preceded by apoptosis of Deiters' and pillar cells. Taken together, these findings detail the morphological changes in the organ of Corti after TNF-α treatment, and provide an in vitro model of inflammatory-induced ototoxicity. 

Tumor Necrosis Factor-α-Induced Ototoxicity in Mouse Cochlear Organotypic Culture.

The sigmoid sinus diverticulum (SSD) is an increasingly recognized cause of pulsatile tinnitus (PT). Surgical reconstruction of the sigmoid sinus wall has been found to be highly effective for SSD; however, surgical techniques still need to be refined to reduce the incidence of serious postoperative complications. Moreover, scrutinizing more cases of SSD is desirable for establishing the diagnostic criteria and standardizing the surgical technique. This study was retrospectively undertaken in 28 patients who were diagnosed with SSD upon computed tomography angiography (CTA) and digital subtraction angiography findings at Beijing Tongren Hospital in China. A majority of patients (20/28) presented with SSD and accompanying sigmoid sinus wall dehiscence (SSWD). Twenty-five patients opted to undergo sigmoid sinus wall reconstruction, and 3 patients refused surgery. Following surgery, 17 patients experienced complete resolution of PT, 3 patients experienced partial resolution, and 5 patients experienced no change in PT. No serious complications were found postoperatively. A comparative analysis of the preoperative and postoperative CTA findings suggested that completely resolving SSD and the accompanying SSWD resulted in the elimination of PT. In conclusion, SSD is generally accompanied by SSWD. Sigmoid sinus wall reconstruction is a safe and effective approach for the treatment of SSD. During surgery, completely resolving both SSD and SSWD is advisable, and maintaining the normal diameter of the sigmoid sinus is imperative. 

Surgical treatment of pulsatile tinnitus caused by the sigmoid sinus diverticulum: a preliminary study.

Superior semicircular canal dehiscence (SSCD) is gradually recognized by otologists in recent years. The patients with SSCD have a syndrome comprising a series of vestibular symptoms and hearing function disorders which can be cured by the operation. In this study, we evaluated the characteristics of patients with SSCD and determined the effectiveness of treating this syndrome by resurfacing the canal via the transmastoid approach using a dumpling structure.

Transmastoid approach for resurfacing the superior semicircular canal dehiscence with a dumpling structure.

Cochlear hair cell loss results in the secondary loss of spiral ganglion cells (SGCs). The death of these SGCs is due to apoptosis. The E2F1-cyclin dependent kinase 1 (CDK1) pathway is believed to represent an important mechanism of neuronal cell death. However, the role of this pathway in spiral ganglion neuronal apoptosis has not yet been reported. In this study, we deafened guinea pigs with a subcutaneous injection of kanamycin followed by an intravenous infusion of furosemide and then assayed the expression levels of cleaved caspase-3, E2F1, CDK1 and cleaved caspase-9 during the induced SGC apoptosis. Our results revealed that co-administration of kanamycin and furosemide rapidly induced hair cell loss in the guinea pigs and then resulted in a progressive loss of SGCs. Expression levels of E2F1 and CDK1 were obviously up-regulated at 1 and 3 days after deafening. Cleaved caspase-9 also increased robustly 1 or 2 weeks after the deafening procedure. The up-regulation of E2F1, CDK1 and cleaved caspase-9 was significantly attenuated by the systemic injection of CR8 (1mg/kg/day, intraperitoneally) starting at 5min after deafening. These findings indicate that the activation of the E2F1-CDK1 pathway and cell cycle re-entry contributes to the apoptosis of SGCs and that the selective inhibition of this signaling cascade may represent an attractive therapeutic strategy. CR8 has the potential to protect SGCs from apoptosis. 

E2F1-CDK1 pathway activation in kanamycin-induced spiral ganglion cell apoptosis and the protective effect of CR8.

To evaluate clinical characteristics and present surgical outcomes of PT caused by sigmoid sinus wall dehiscence (SSWD).

Sigmoid Sinus Wall Reconstruction for Pulsatile Tinnitus Caused by Sigmoid Sinus Wall Dehiscence: A Single-Center Experience.

Impairments of the inner ear result in sensorineural hearing loss and vestibular dysfunction in humans. A large proportion of these disorders are congenital, and involve both auditory and vestibular systems. Therefore, genetic interventions to correct deficits must be administered during early developmental stages. In this study, we evaluated inner ear gene transfer in neonatal mice by canalostomy using an adeno-associated virus serotype 8 (AAV8) vector. AAV8 with the green fluorescence protein (GFP) gene was inoculated into the inner ear of the neonatal mice through the posterior semicircular canal (canalostomy). At 30 days following surgery, animals were subjected to swim tests and auditory brainstem response measurements. Then, the animals were euthanized and temporal bones were harvested for whole-mount preparation. GFP expression and morphological changes in the inner ear were assessed by immunohistochemistry. After surgery, no signs of vestibular dysfunction were found, and there were no significant differences in the auditory brainstem response threshold between AAV8-inoculated ears and nonsurgery ears. In the surgery ears, extensive GFP expression and no morphological lesions were detected in the cochlear and vestibular end organs. Robust GFP expression was found in inner hair cells, marginal cells, vestibular hair cells, and vestibular supporting cells. In conclusion, AAV8 inoculation through canalostomy into the inner ears of neonatal mice led to extensive overexpression of exogenous genes in the inner ear without affecting hearing or vestibular function. It serves as a promising approach for gene therapy of congenital cochleovestibular diseases.

Cochleovestibular gene transfer in neonatal mice by canalostomy.

Noise-induced hearing loss (NIHL) severely impacts the quality of life of affected individuals. Oxidative stress resulting from noise exposure is a significant cause of NIHL. Although histone deacetylase (HDAC) inhibitors were shown to protect against NIHL, the underlying mechanism remains unclear, and it is not known how they act on noise-induced oxidative stress. In the current study, we investigated the expression levels of acetyl-histone H3 (Lys9) (H3-AcK9), histone deacetylase 1 (HDAC1), and 3-nitrotyrosine (3-NT), an oxidative stress marker, in a guinea pig model of NIHL using immunohistology and Western blotting. We then assessed the effects of systemic administration of the HDAC inhibitor, sodium butyrate (SB), on noise-induced permanent threshold shifts (PTS), hair cell (HC) loss, and changes in the above mentioned markers. The results showed that SB attenuated noise-induced PTS and outer hair cell loss. SB treatment promoted H3-AcK9 expression and repressed HDAC1 expression in the nuclei of HCs and Hensen's cells after noise exposure. Furthermore, SB attenuated the noise-induced increase of 3-NT expression in HCs and Hensen's cells. These findings suggest that SB protects against NIHL by reversing the noise-induced histone acetylation imbalance and inhibiting oxidative stress in cochlear HCs and Hensen's cells. SB treatment may represent a potential strategy to prevent and treat NIHL.

The histone deacetylase inhibitor sodium butyrate protects against noise-induced hearing loss in Guinea pigs.

The damaged vestibular sensory epithelium of mammals has a limited capacity for spontaneous hair cell regeneration, which largely depends on the transdifferentiation of surviving supporting cells. Little is known about the response of vestibular supporting cells to a severe insult. In the present study, we evaluated the impact of a severe ototoxic insult on the histology of utricular supporting cells and the changes in innervation that ensued. We infused a high dose of streptomycin into the mouse posterior semicircular canal to induce a severe lesion in the utricle. Both scanning electron microscopy and light microscopy of plastic sections showed replacement of the normal cytoarchitecture of the epithelial layer with a flat layer of cells in most of the samples. Immunofluorescence staining showed numerous cells in the severely damaged epithelial layer that were negative for hair cell and supporting cell markers. Nerve fibers under the flat epithelium had high density at the 1 month time point but very low density by 3 months. Similarly, the number of vestibular ganglion neurons was unchanged at 1 month after the lesion, but was significantly lower at 3 months. We therefore determined that the mouse utricular epithelium turns into a flat epithelium after a severe lesion, but the degeneration of neural components is slow, suggesting that treatments to restore balance by hair cell regeneration, stem cell therapy or vestibular prosthesis implantation will likely benefit from the short term preservation of the neural substrate.

Guo-Peng Wang

Department of Otolaryngology-Head and Neck Surgery,
Beijing Friendship Hospital,
Department of Otolaryngology-Head and Neck Surgery, Beijing Friendship Hospital

Capital Medical University

Canalostomy As a Surgical Approach to Local Drug Delivery into the Inner Ears of Adult and Neonatal Mice

Guo-Peng Wang

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Otolaryngology-Head and Neck Surgery,Beijing Friendship Hospital,Department of Otolaryngology-Head and Neck Surgery, Beijing Friendship Hospital

Capital Medical University

Canalostomy As a Surgical Approach to Local Drug Delivery into the Inner Ears of Adult and Neonatal Mice

Department of Otolaryngology-Head and Neck Surgery,
Beijing Friendship Hospital,
Department of Otolaryngology-Head and Neck Surgery, Beijing Friendship Hospital