Mice ; Animals ; Spiral Ganglion/physiology* ; Cochlea/physiology* ; Neurons

Animals ; Apoptosis ; Cochlea ; Estrogens/pharmacology* ; Mice ; Mice, Inbred C57BL ; Neurons ; Spiral Ganglion

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.
Cochlea ; Ear, Inner ; Ear, Middle ; Eosine Yellowish-(YS) ; Evoked Potentials, Auditory, Brain Stem ; Ginkgo biloba ; Hearing Loss* ; Hearing Loss, Sensorineural ; Hearing* ; Hematoxylin ; Immunohistochemistry ; Models, Animal ; Rats, Sprague-Dawley ; Sirtuin 1* ; Spiral Ganglion

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.
Adult ; Animals ; Cochlea ; Deafness ; Hearing Loss ; Humans ; In Vitro Techniques* ; Mice* ; Nestin ; Neural Stem Cells* ; Neuroglia ; Neurons ; Regeneration ; Spiral Ganglion* ; Stem Cells

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.
Animals ; Bone Marrow ; Clinical Study ; Electric Stimulation ; Hair ; Hearing Loss ; Hearing Loss, Sensorineural ; Hearing ; Humans ; Mesenchymal Stem Cell Transplantation ; Mesenchymal Stromal Cells ; Pilot Projects ; Spiral Ganglion ; Stem Cell Transplantation

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.
Animals ; Apoptosis ; Blotting, Western ; Brain Stem ; Cochlea ; Ear, Inner ; Eosine Yellowish-(YS) ; Hair Cells, Auditory, Outer ; Hearing* ; Hematoxylin ; Hip ; Injections, Intramuscular ; Mice* ; Nerve Growth Factor* ; Neurons ; Real-Time Polymerase Chain Reaction ; Spiral Ganglion ; Water

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.
Animals ; Benzazepines ; pharmacology ; Cells, Cultured ; Cochlea ; cytology ; Neurons ; drug effects ; Rats ; Receptors, Dopamine ; metabolism ; Receptors, GABA-A ; metabolism ; Receptors, N-Methyl-D-Aspartate ; metabolism ; Sodium Salicylate ; toxicity ; Spiral Ganglion ; drug effects

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.
Acoustics ; Brain ; Cisplatin ; Cochlea ; Cochlear Implants ; Ear, Inner ; Electrodes ; Genetic Therapy* ; Hair ; Hearing Loss, Sensorineural ; Hearing* ; HSP70 Heat-Shock Proteins ; Nerve Endings ; Nerve Growth Factors ; Publications ; Spiral Ganglion ; Synapses ; Treatment Outcome

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.
Animals ; Apoptosis ; Cisplatin ; pharmacology ; Cochlea ; metabolism ; Guinea Pigs ; Proto-Oncogene Proteins c-bcl-2 ; metabolism ; Spiral Ganglion ; drug effects ; metabolism ; bcl-2-Associated X Protein ; metabolism

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.
Animals ; Bone Marrow ; Cell Differentiation ; Cochlea ; Cochlear Nerve ; Colforsin ; Ear ; Fibroblast Growth Factor 2 ; Guinea Pigs* ; Hair ; Hearing Loss ; Hearing Loss, Sensorineural ; Humans ; Ion Channels ; Mammals ; Mastoid ; Mesenchymal Stromal Cells* ; Neomycin ; Neurons ; Organ of Corti ; Regeneration* ; Scala Tympani ; Sensory Receptor Cells ; Sodium ; Spiral Ganglion ; Transplantation ; Transplants