Clinical Safety and Efficacy of Autologous Bone Marrow-Derived Mesenchymal Stem Cell Transplantation in Sensorineural Hearing Loss Patients

Stem cell transplantation represents a promising therapy for several degenerating and necrotic diseases. In several animal studies, we could find hearing restoration after inoculation of the mesenchymal stem cells' as well as mesenchymal stem cells' differentiation of hair cells and spiral ganglion. But until now, no clinical study has been reported directly for the human being. In this pilot studies, we applied mesenchymal stem cells to human beings trans-venously. Although we verified the safety of the autologous bone marrow stem cell transplantation in sensorineural hearing loss patients but we could not achieve significant improvement in hearing.

The Protective Effect of Egb 761 Against 3-Nitropropionic Acid-Induced Hearing Loss: The Role of Sirtuin 1

OBJECTIVES: Local administration of 3-nitropropionic acid (3-NP) to the inner ear induces sensorineural hearing loss. Several studies have shown the otoprotective effects of ginkgo biloba extract EGb 761. Moreover, EGb 761 has been reported to activate Sirtuin 1 (SIRT1). The present study was designed to investigate whether EGb 761 prevents 3-NP-induced sensorineural hearing loss and determine its effects on the expression of SIRT1. METHODS: Sprague Dawley rats were divided into four experimental groups: control group receiving vehicle of 3-NP, EGb group receiving EGb 761, 3-NP group receiving 3-NP, and EGb+3-NP group receiving EGb 761 and 3-NP. EGb 761 was given orally for 5 days. The 3-NP solution was injected into the tympanum 3 days after the start of EGb 761 administration. The auditory brainstem response was recorded before and after the injection. At 4 weeks after the administration of 3-NP or vehicle of 3-NP, cochleae were harvested, and hematoxylin and eosin staining and immunohistochemistry for SIRT1 antibody were performed. RESULTS: EGb+3-NP group showed significantly lower threshold shifts than 3-NP group. There was a significant preservation of type II fibrocytes and spiral ganglion cells in EGb+3-NP group than in 3-NP group. In EGb+3-NP group, there was a significantly greater number of SIRT1 immunopositive type II fibrocytes and spiral ganglion cells than in 3-NP group. Calculating the percentage of SIRT1 immunoreactive type II fibrocytes and spiral ganglion cells in viable type II fibrocytes and spiral ganglion cells, respectively, EGb+3-NP group showed significantly higher SIRT1 immunoreactive cells than 3-NP group. CONCLUSION: These results suggest that EGb 761 may prevent hearing loss induced by 3-NP in an acute ototoxic animal model, which appears to be related with SIRT1 expression.

The Presence of Neural Stem Cells and Changes in Stem Cell-Like Activity With Age in Mouse Spiral Ganglion Cells In Vivo and In Vitro

OBJECTIVES: Spiral ganglion neurons (SGNs) include potential endogenous progenitor populations for the regeneration of the peripheral auditory system. However, whether these populations are present in adult mice is largely unknown. We examined the presence and characteristics of SGN-neural stem cells (NSCs) in mice as a function of age. METHODS: The expression of Nestin and Ki67 was examined in sequentially dissected cochlear modiolar tissues from mice of different ages (from postnatal day to 24 weeks) and the sphere-forming populations from the SGNs were isolated and differentiated into different cell types. RESULTS: There were significant decreases in Nestin and Ki67 double-positive mitotic progenitor cells in vivo with increasing mouse age. The SGNs formed spheres exhibiting self-renewing activity and multipotent capacity, which were seen in NSCs and were capable of differentiating into neuron and glial cell types. The SGN spheres derived from mice at an early age (postnatal day or 2 weeks) contained more mitotic stem cells than those from mice at a late age. CONCLUSION: Our findings showed the presence of self-renewing and proliferative subtypes of SGN-NSCs which might serve as a promising source for the regeneration of auditory neurons even in adult mice.

A study on toxic effects of sodium salicylate on rat cochlear spiral ganglion neurons: dopamine receptors mediate expressions of NMDA and GABAreceptors / 生理学报

The aim of the present study was to observe whether dopamine receptor (DR) was involved in the effects of sodium salicylate (SS) on the expressions of N-methyl-D-aspartic acid (NMDA) and γ-aminobutyric acid (GABA) receptors in rat cochlear spiral ganglion neurons (SGNs). Forty-eight hours after primary culture of rat SGNs, immunofluorescence technique was applied to detect expressions of DR1 and DR2, the two subtypes of dopamine receptors. Western blot was performed to assess NMDA receptor NR1 subunit and GABAreceptor subunit α2 (GABRα2) protein expressions in the SGNs after the treatments of SS alone or in combination with DR antagonists. The results demonstrated that: (1) The DR1 and DR2 were expressed in the bodies and axons of the SGN; (2) After the treatment with SS, the surface protein expressions of GABRα2 and NR1 were decreased by 44.69% and 21.57%, respectively, while the total protein expressions showed no significant changes; (3) Neither SS + SCH23390 (DR1 antagonist) group nor SS + Eticlopride (DR2 antagonist) group showed significant differences in GABRα2 and NR1 surface protein expressions compared with the control group. These results suggest that SS regulates the surface GABAand NMDA receptors trafficking on SGN, and the mechanism may involve DR mediation.

Gene Therapy for Hearing Protection / 대한이비인후과학회지

Sensorineural hearing loss (SNHL) does not recover and only few exceptions exist. It is mostly due to the reason that hair cells in the cochlea cannot regenerate once damaged. Therefore, clinical approaches for SNHL mostly rely on the implantable or external device to deliver sound to brain. Despite the advance of technology, current strategy does not replicate the sound perception of naïve inner ear. To overcome this issue, novel trials to protect or rescue hair cells from the ototoxic insults are investigated. One of these is gene therapy. Protective gene therapy has been applied to several ototoxic insults, but some trials have shown negative effect. Gene therapy using neurotrophin, one of the growth factor, has been expected to show protective effect against acoustic overexposure. But unregulated and untargeted expression of Ntf3 revealed adverse effect showing deterioration of nerve ending and synapse. Meanwhile, gene therapies have been adopted and tried for cisplatin ototoxicity. Most of the studies has been shown promising outcome. Also several studies have shown protective effect of gene therapy for aminoglycoside ototoxicity. Recent publication showed that heat-shock protein 70 was effective in preventing aminoglycoside ototoxicity. Furthermore, use of gene therapy expands to the field of cochlear implant, in which it can be used as an enhancer of treatment outcome. Application of neurotrophins resulted in increase of spiral ganglion densities as well as migration of peripheral nervous fibers to the location which would be closer to the electrode when implanted.

Hearing Improvement in A/J Mice via the Mouse Nerve Growth Factor

OBJECTIVES: To investigate the otoprotective effects of mouse nerve growth factor (mNGF) in A/J mice. METHODS: The mice at postnatal day 7 (P7) were randomly separated into a mNGF treated group (mNGF group) and a distilled water (for injection) treated group (control group). The mNGF dissolved in distilled water or distilled water alone was given to the mice once every other day from P7 by intramuscular injection in the hips. The otoprotective effects of mNGF in A/J mice were observed in a time course manner. The thresholds of auditory-evoked brainstem response (ABR) were tested from the age of the 3rd to the 8th week. Sections of the inner ears were stained by hematoxylin and eosin, and spiral ganglion neurons (SGNs) were observed at the age of the 3rd, the 6th,and the 8th week. Counts of whole mount outer hair cells (OHCs) in the cochleae were made at the age of 8 weeks. Expression of apoptosis related genes was determined by quantitative real-time polymerase chain reaction and Western blotting. RESULTS: ABR thresholds of the mNGF group were significantly lower than those of the control group at the age of the 6th and the 8th week. Moreover, the mNGF preserved OHC and SGN in the mouse cochleae in this period. Further experiments showed that the expression of caspase genes (including caspase-3) was inhibited in the mouse inner ears in the mNGF group. CONCLUSION: The mNGF improves hearing in A/J mice by preserving SGN and OHC in the cochleae.

Effectiveness of cisplatin on the expressions of Bcl-2 and Bax in cochlea and spiral ganglion cells of guinea pigs / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#To investigate the effectiveness of cisplatin on the expressions of Bcl-2 and Bax in cochlea and spiral ganglion cells (SGC) of guinea pigs.@*METHOD@#Twenty guinea pigs were randomly divided into cisplatin (n = 10) and control groups (n = 10). Cisplatin group were administrated with a dose of intraperitoneal injection of 16 mg/kg, while the control group were received intraperitoneal injection of normal saline as placebo. Before and 7 days following injections, the ototoxic effect was measured with distortion product otoacoustic emission (DPOAE). Bcl-2, Bax in cochlea were detected by Western Blot. Immunohistochemical staining was used to detect the protein levels of Bcl-2 and Bax in spiral ganglion cells.@*RESULT@#In control and cisplatin group, Bcl-2 protein levels were 0.727 8 ± 0.016 9 and 0.467 6 ± 0.020 1, Bax protein levels were 0.384 8 ± 0. 0217 and 0.735 6 ± 0.022 3 in cochlea respectively, both P < 0.01. In Control and cisplatin group, the grey values of Bcl-2 in SGC were 99.00 ± 2.42 and 149.80 ± 2.37 respectively, the grey values of Bax were 154.50 ± 2.80 and 104.50 ± 3.09 respectively, both P < 0.05.@*CONCLUSION@#Decreased expression of Bcl-2 and increased expression of Bax may be involved in cisplatin-induced apoptosis in cochlea and SGC of guinea pigs.

The effect of sodium salicylate on the expression of GABAa receptor subunits in cochlear spiral ganglion neurons / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#To investigate mRNA expression of GABAa receptor(GABAaR) subunits in the rat cochlear spiral ganglion neurons (SGN) and explore the effect of sodium salicylate (SS) on the expression of GABAaR subunits.@*METHOD@#The realtime fluorescent quantitative PCR (FQ-PCR) was used to detect mRNA expression of twelve GABAaR subunits in the newborn rat SGN and then investigate mRNA expression of GABAaR subunits after treatment with 5 mmol/L SS for 15 min, 30 min, 1 h, 3 h and 6 h in the primary culture SGN.@*RESULT@#(1) GABAaR subunits of α1-6, β1-3, and γ1-3 were detected in the SGN, and the expression of GABAaR subunits was lower than those in the cerebral cortex. In the subunit α family of GABAaR, the expression rank was α2>α3/α5>α4>a1>α6, and the expression of α3 and α5 had no difference (P>0. 05). In the subunit β family, the expression rank was β3>β2>β1. In the subunit γ family, the expression rank was γ1>γ2>γ3. (2) The expression of all subunits of GABAa receptor was obviously fluctuated excepting subunit α5 after treatment with SS. At 15 min post-SS, α1, α2 , β1 and γ1-3 were upregulated, and α3 was downregulated; At 30 min post-SS, α3, β1 and β3 were upregulated, and γ1 was downregulated; At 1 h post-SS, β2 was upregulated and γ3 was downregulated; At 3 h post-SS, β1 and β2 were upregulated, and α3 and γ2 were downregulated; At 6 h post-SS, αl, α3 ,β2, β3 and γ1 were upregulated, and α2, α4 and β1 were downregulated.@*CONCLUSION@#The mRNA of GABAaR was expressed in the rat SGN, and the expression of GABAaR subunits was lower in SGN than the cerebral cortex. SS could alter the GABAaR expression quantity in rat SGN; Most of the subunits expression were elevated obviously in the early post SS (15 min), followed by a slight fluctuation.

The expression and significance of VIP and its receptor in the cochlea of different degrees of chronic alcoholism rats / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#To determine whether chronic alcoholism alters the expression levels of Vasoactive intestinal polypeptide (VIP) and its receptor (VIPR1) in the cochlea of chronic alcoholism rats.@*METHOD@#We measured their expression levels in 30 SD rats, in which we created models of different degrees of chronic alcoholism. We investigated the presence of the mRNA of VIP in the cochlea of chronic alcoholism rats and controls by reverse transcription-polymerase chain reaction (RT-PCR) method. We investigated the presence of proteins of VIPR1 in poisoned rats and controls by western blot. We also evaluated the local distribution of VIP cells by immunohistochemistry.@*RESULT@#We found that the levels of VIP and VIPR1 were downregulated in the chronic alcoholism groups compared to the controls group. The differences in some expression levels were significant different between chronic alcoholism rats and control rats. Moreover, at different degrees of alcohol poisoning in rats, the contents of VIP and VIPR1 differed. Decreased levels of VIP and VIPR1 were detected in the deep chronic alcoholism group compared to the group with low-degree poisoning (P 0.05).@*CONCLUSION@#These results suggest that VIP and VIPR1 play an important role in the auditory function in rats with chronic alcoholism. Chronic alcoholism may cause a peptide hormone secretion imbalance in the auditory system, eventually leading to hearing loss.

Noise-Induced Neural Degeneration and Therapeutic Effect of Antioxidant Drugs

The primary site of lesion induced by noise exposure is the hair cells in the organ of Corti and the primary neural degeneration occurs in synaptic terminals of cochlear nerve fibers and spiral ganglion cells. The cellular basis of noise-induced hearing loss is oxidative stress, which refers to a severe disruption in the balance between the production of free radicals and antioxidant defense system in the cochlea by excessive production of free radicals induced by noise exposure. Oxidative stress has been identified by a variety of biomarkers to label free radical activity which include four-hydroxy-2-nonenal, nitrotyrosine, and malondialdehyde, and inducible nitric oxide synthase, cytochrome-C, and cascade-3, 8, 9. Furthermore, oxidative stress is contributing to the necrotic and apoptotic cell deaths in the cochlea. To counteract the known mechanisms of pathogenesis and oxidative stress induced by noise exposure, a variety of antioxidant drugs including oxygen-based antioxidants such as N-acetyl-L-cystein and acetyl-L-carnitine and nitrone-based antioxidants such as phenyl-N-tert-butylnitrone (PBN), disufenton sodium, 4-hydroxy PBN, and 2, 4-disulfonyl PBN have been used in our laboratory. These antioxidant drugs were effective in preventing or treating noise-induced hearing loss. In combination with other antioxidants, antioxidant drugs showed a strong synergistic effect. Furthermore, successful use of antioxidant drugs depends on the optimal timing of treatment and the duration of treatment, which are highly related to the time window of free radical formation induced by noise exposure.

Regenerative Cell Therapy for the Sensorineural Hearing Loss / 한양의대학술지

Sensorineural hearing loss is the most common disability in the world and nearly one third of all individuals over the age of 65 are affected. For hearing handicapped people, many devices (hearing aid, cochlear implant, middle ear implant etc.) have been developed to reduce or overcome the disability. But these devices do not give perfect benefit to the patients functionally and there are aesthetic problems. That is why researchers have interest in regenerative measures to restore or prevent hearing loss. Recently there were fruitful results from gene and stem cell therapy research for hearing loss. Gene therapy with Atoh 1 gene and transplantation of stem cells into the cochlea regenerate damaged hair cells and morphologically restore spiral ganglion neurons allowing functional hearing in the deaf animal model. Based on these results, many countries including Korea have done clinical trials in deaf patients. The past ten years have shown an incredible advancement in medical biotechnology in the otologic field and this progress may someday substitute the medical devices for the hard of hearing patients.

Neural-Induced Human Mesenchymal Stem Cells Promote Cochlear Cell Regeneration in Deaf Guinea Pigs

OBJECTIVES: In mammals, cochlear hair cell loss is irreversible and may result in a permanent sensorineural hearing loss. Secondary to this hair cell loss, a progressive loss of spiral ganglion neurons (SGNs) is presented. In this study, we have investigated the effects of neural-induced human mesenchymal stem cells (NI-hMSCs) from human bone marrow on sensory neuronal regeneration from neomycin treated deafened guinea pig cochleae. METHODS: HMSCs were isolated from the bone marrow which was obtained from the mastoid process during mastoidectomy for ear surgery. Following neural induction with basic fibroblast growth factor and forskolin, we studied the several neural marker and performed electrophysiological analysis. NI-hMSCs were transplanted into the neomycin treated deafened guinea pig cochlea. Engraftment of NI-hMSCs was evaluated immunohistologically at 8 weeks after transplantation. RESULTS: Following neural differentiation, hMSCs expressed high levels of neural markers, ionic channel markers, which are important in neural function, and tetrodotoxin-sensitive voltage-dependent sodium currents. After transplantation into the scala tympani of damaged cochlea, NI-hMSCs-injected animals exhibited a significant increase in the number of SGNs compared to Hanks balanced salt solution-injected animals. Transplanted NI-hMSCs were found within the perilymphatic space, the organ of Corti, along the cochlear nerve fibers, and in the spiral ganglion. Furthermore, the grafted NI-hMSCs migrated into the spiral ganglion where they expressed the neuron-specific marker, NeuN. CONCLUSION: The results show the potential of NI-hMSCs to give rise to replace the lost cochlear cells in hearing loss mammals.

Effects of acute hypoxia on potassium channels in spiral ganglion cells of SD rats / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>The present study was to investigate the effects of acute hypoxia on the electrophysiological properties and outward current of spiral ganglion cell (SGC).</p><p><b>METHODS</b>SGC of newborn's Sprague Dawley (SD) rats were isolated and digested, primary cultured neurons for 8 h. By perfusion with physical saline solution containing no glucose and low oxygen, SGNs model of acute hypoxia was established. The whole-cell patch clamp recording was used to clarify the effect of hypoxia on the outward currents of SGC.</p><p><b>RESULTS</b>The outward current of SGC showed characteristics of outward rectification, which contained two major components, one sensitive to the big conductance Ca²⁺-activated K⁺ channels (BKCa) which blocked by TEA, and the other could be suppressed by the KV channel blocker 4-AP. When holding at -60 mV, acute hypoxia increased the outward current of SGC in a voltage-dependent manner, which mainly increased the amplitude of the current activated by the votage ranged from 0 mV to +60 mV, and increased the amplitude of outward current from (1 160.0 ± 129.1) pA to (2 428 ± 239.3) pA (n = 9, P < 0.01) at holding potential of -60mV. By perfusion with the Potassium channel blocker TEA or 4-AP, the former could significantly reduced the increasing of outward currents induced by hypoxia on the SGC, the latter had no significant effect on the outward current increased by the hypoxia.</p><p><b>CONCLUSIONS</b>These results suggest that acute hypoxia causes neuron hyperpolarization possibly by activating big conductance BKCa of the SGC. When the BKca channels are activated, K⁺ effluxes increase, which induces cell membrane hyperpolarization, and decreases cell excitability, which may affect the conducting function of SGC.</p>

Age-related expression of plasma membrane Ca(2+) -ATPase isoform 2 in the cochleas of C57BL/6J mice / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To investigate the location and distribution of plasma membrane Ca²⁺ -ATPase isoform 2(PMCA2) in the cochleas of C57BL/6J mice at various ages (4w, 14w, 22w, 45w), and to reveal the relationship of PMCA2 and age-related hearing loss (AHL).</p><p><b>METHODS</b>The distribution of PMCA2 in the cochleas of C57BL/6J mice was detected by immunohistochemistry at various ages (4w, 14w, 22w, 45w). Real-time polymerase chain reaction (Rt-PCR) was used to detect the level of PMCA2 mRNA in the cochleas of C57BL/6J mice at the ages of 4, 14, 22 and 45 weeks old respectively. Using SPSS17.0 software for statistical analysis.</p><p><b>RESULTS</b>PMCA2 was mainly located in the hear cells, stria vascularis, and spiral ganglion cells. Faint labeling of PMCA2 was also observed in spiral ligament. Hair cells missed and the number of spiral ganglion cells reduced with age. Expression of PMCA2 in the cochleas of C57BL/6J mice also showed age-related decreasing. The results of Rt-PCR demonstrated the expression of mRNA of gene (Atp2b2) at 14 weeks age was significantly less than 4 week-old mice cochlears (P<0.05). The expression of mRNA of gene (Atp2b2) at 22 weeks age was significantly less than 14 week-old mice cochlears (P<0.05). The expression of mRNA of gene (Atp2b2) at 45 weeks age was significantly less than 14 week-old mice cochlears (P<0.01).</p><p><b>CONCLUSIONS</b>PMCA2 is mainly located in the hear cells, stria vascularis, and spiral ganglion cells. Faint labeling of PMCA2 is also observed in spiral ligament. The expression of PMCA2 demonstrates an age-related decrease with age. The mRNA expression level of PMCA2 gene(Atp2b2) in the cochleas of C57BL/6J mice displayed an age-related decrease. PMCA2 transporters may play a critical role in maintaining the normal morphology of the inner ear and it may be related to AHL.</p>

Effects on survival of shRNA mediated APE/Ref1 gene silencing in rat spiral ganglion cells in oxidative stress / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To investigate the effects of reducing APE/Ref1 expression in the cultures of rat spiral ganglion cells with oxidative damage induced by H(2)O(2).</p><p><b>METHODS</b>Primary cultured rat spiral ganglion cells were infected with small interfering RNA to APE/Ref1 (Ape1siRNA) for 72 h, followed by treating with H(2)O(2) (0, 10, 25, 50, 100 and 300 µmol/L) for 1 h , and then cultured in normal medium for 24 h. Western blot were used to detect the level of APE/Ref1 protein and phosphorylation of histone protein H2AX in the infected cells. The caspase3 activation was tested by spectrophotometric method . The cell viability was determined by MTT and the apoptosis of spiral ganglion cells was determined by terminal-deoxynucleotidyl transferase mediated nick and labeling (TUNEL).</p><p><b>RESULTS</b>Western blot showed that infection with Ape1siRNA resulted in APE/Ref1 reduced expression in the spiral ganglion cells. Exposing spiral ganglion cultures with reduced expression of APE/Ref1 to H(2)O(2) (50, 100, 300 µmol/L) for 1 h resulted in increasing in the phosphorylation of histone protein H2AX. The reduction in APE/Ref1 significantly reduced cell viability in cultures 24 h after 1 h expression to 50-300 µmol/L H(2)O(2). The apoptosis of cells and caspase 3 activity was detected significantly improved.</p><p><b>CONCLUSIONS</b>The induced of APE/Ref1 results in significantly decrease in spiral ganglion cells viability in oxidative stress. The repairing function of APE/Ref1 is necessary for optimal levels of neuronal rat spiral ganglion cells survival.</p>

RAGE, NF-kappaB, p21 expressions in mouse spiral ganglion cells / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#To research advanced glycation end-product receptors (RAGE), NF-kappaB, p21 expressions in C57BL/6j mice cochlea spiral ganglion cells(SGC) ,and then to investigate the presbycusis pathogenesis.@*METHOD@#To take C57BL/6J mice:2 month 25,and 10 month 25. Histological sections were observed the SGC. RAGE, NF-kappaB, p21 were immunohistochemical in the SGC,with IPP6 to IOD.@*RESULT@#(1) The count SGCs of 10 month-old was obviously decreased comparing to 2 month-old, the count of 2 month SGC is 39 +/- 5, 10 month group is 20 +/- 6, P < 0.01; (2) RAGE, NF-kappaB, p21 expressed in spiral ganglion cell,different place with different age,and the means optical density in the 10 month are higher than the 2 month, respectively. The IOD of RAGE expression in 2 month SGC: 0.179 +/- 0.025, 10 month IOD: 0.308 +/- 0.050; The IOD of NF-kappaB expression in 2 month SGC: 0.181 +/- 0.045, 10 month IOD: 0.335 +/- 0.120; The IOD of p21 expression in 2 month SGC: 0.160 +/- 0.023, 10 month IOD: 0.365 +/- 0.031, compare with 2 group, respectively, P < 0.05, and the difference has statistics sense.@*CONCLUSION@#RAGE,NF-kappaB, p21 expressions are in SGCs and increases with the aging of SGCs, suppose RAGE, NF-kappaB, p21 may participate in the process of presbycusis pathogenesis.

Src family kinases affect the expression of Nav1.1 in spiral ganglion neurons / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#To investigated the effects of Src family kinases on the expression of mRNA and protein of Nav1.1 in spiral ganglion neurons.@*METHOD@#RT-PCR and Western blot techniques respectively explored the level of expression of mRNA and protein of Nav1.1 in spiral ganglion neurons by Src family kinases inhibitor.@*RESULT@#An application of the inhibitor of Src family kinases which was PP2 (10 micromol/L) and SU6656 (2 micromol/L) gived rise to the mRNA decreasing to 26% +/- 0.8% and 36% +/- 1.5% respectively (P < 0.05), and protein reducing to 39% +/- 12.5% and 53% +/- 1.7% severally (P < 0.05).@*CONCLUSION@#Administration of the inhibitor of Src family kinases could decrease the expression of mRNA and protein of Nav1.1 in spiral ganglion neurons.

The expression levels of three T-type calcium channel receptors in inner ear of C57BL/6J mice with age / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#To explore the expression levels of three T-type calcium channel receptors (α1G; α1H; α1I) in the cochlea and spiral ganglion neurons of C57BL/6J mice with different ages.@*METHOD@#Thirty cases of C57BL/6J mice were divided into three groups (6-8 W, 24-26 W, 42-44 W) according to the age. The expressions of three T-type calcium channel receptors were quantified by RT-PCR after hearing thresholds measured by ABR.@*RESULT@#Three receptors were detected in the cochlea and spiral ganglion neurons of 6-8 W C57BL/6J mice. The quantitative results showed that the expression levels of α1H and α1I were highest among three receptors in spiral ganglion neurons and in the cochlea respectively. The expression levels of three receptors significantly decreased with age,especially at the age of 4244 W.@*CONCLUSION@#The expression of T-type calcium channel receptors reduced with age in the inner ear of C57BL/6J mice.

Damage of Spiral Ganglion Cell Induced by Ouabain Application in Cat / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Auditory neuropathy is a hearing disorder characterized by the absence or the marked impairment of the auditory brainstem responses with the preservation of the cochlear microphonics (CMs) and otoacoustic emissions. This suggests that outer hair cell (OHC) function is normal but proximal auditory function to OHCs is impaired. It is assumed that the lesion is localized at the level of the inner hair cells (IHCs), auditory nerve fibers, or the synapse between them. This study was aimed to observe the change of hearing threshold and pathology of spiral ganglion cell induced by ouabain application, and present basic data to explain the auditory neuropathy. MATERIALS AND METHOD: Twenty ears of twenty normal hearing cats were used in this study. Cats were treated with 100 microL ouabain (1 mM) applied on the round window. After three days, compound action potential (CAP) and CM were measured and the cochlea was obtained. Pathologic change of spiral ganglion cell was evaluated under light microscope after H&E stain. Normal saline was injected for the control group. RESULTS: In the ouabain group, CAP threshold was increased in all tested frequencies (p0.05). There was significant difference between CAP and CM threshold shift (p<0.001). In the control group, there was no significant difference in CAP and CM thresholds. Light microscopic findings show that the condensed chromatin and nuclear fragments of spiral ganglion cells of an ear was exposed to ouabain, and outer hair cell and inner hair cell were not damaged. CONCLUSION: This study shows that the CAP threshold was significantly increased but the CM threshold was not changed in the ouabain group. Ouabain induced damage of spiral ganglion cells. This study is not sufficient to explain auditory neuropathy because threshold shift of CAP is not obvious, but it would be helpful to explain that selective damage of spiral ganglion cell would be the mechanism of auditory neuropathy.

Precursor brain-derived neurotrophic factor reduces survival and axonal sprouting of rat spiral ganglion neurons in vitro / 生理学报

The aim of the present study was to investigate the effect of precursor brain-derived neurotrophic factor (proBDNF) on survival and neurite outgrowth of cultured rat spiral ganglion neurons (SGNs). Spiral ganglions (SG) were collected from postnatal day 5 Sprague Dawley (SD) rats, then enzymatically digested and suspended. Dissociated SGNs were plated on poly-D-lysine/laminin coated eight-well chamber plates and maintained at 37 °C for 4 h to promote the attachment of the neurons. Cultured SGNs were randomly divided into five groups: control group, BDNF group (BDNF 10 ng/mL), C10 group (proBDNF 10 ng/mL), C50 group (proBDNF 50 ng/mL), and C100 group (proBDNF 100 ng/mL). All groups were incubated in a serum-free medium. 48 h after incubation, SGNs were fixed and stained for βIII tubulin. Immunostaining of the cultured SGNs showed that, compared with the control group, the cellular survival of C50 group and C100 group were significantly reduced (P < 0.001). Furthermore, surviving numbers of the three proBDNF-treated groups were all lower than the BDNF group. In order to assess the effect of proBDNF on cell morphology, SGNs were divided into two categories: SGNs with or without neurites. The results demonstrated that proBDNF significantly increased the proportions of SGNs without neurites in C10, C50 and C100 groups compared with that in control group (P < 0.001). In addition, c-Jun N-terminal kinase (JNK) inhibitor, SP600125 (20 μmol/L) significantly increased the surviving number of SGNs in C50 group. These results suggest that proBDNF reduces the survival rate of cultured SGNs and inhibits the sprouting of neurites. Furthermore, the inhibition of JNK signaling attenuates the effect of proBDNF on SGNs survival.