Bhlhe40 protects cochlear hair cell-like HEI-OC1 cells against H_(2)O_(2) ‑triggered oxidative injury

Background:Cochlear hair cell injury is a common pathological feature of hearing loss.The basic helix-loop-helix family,member e40(Bhlhe40),a gene belonging to the basic helix-loop-helix(bHLH)family,exhibits strong transcriptional repression activity.Methods:Oxidative damage,in House Ear Institute-Organ of Corti 1(HEI-OC1)cells,was caused using hydrogen peroxide(H2O2).The Ad-Bhlhe40 particles were constructed to overexpress Bhlhe40 in HEI-OC1 cells.Various assays including cell counting kit-8(CCK-8),terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay(TUNEL),flow cytometry,immunofluorescence,and corresponding commercial kits were employed to investigate the impacts of Bhlhe40 on cell viability,apoptosis,oxidative stress levels,mitochondrial membrane potential and cellular senescence.Additionally,a dual-luciferase reporter assay was performed to confirm the targeting of the histone deacetylases 2(Hdac2)by Bhlhe40.Results:The results revealed that Bhlhe40 was downregulated in H_(2)O_(2)-treated HEI-OC1 cells,but its overexpression improved cell viability and mitigated H_(2)O_(2)-induced oxidative injury in HEI-OC1 cells with increase of superoxide dismutase(SOD),catalase(CAT)and glutathione peroxidase(GPx)activities and decrease of reactive oxygen species(ROS)levels.Besides,overexpression of Bhlhe40 suppressed H_(2)O_(2)-triggered cell senescence,as evidenced by the fact that the upregulation of P53,P21,and P16 in HEI-OC1 cells treated with H2O2 were all alleviated by Bhlhe40 overexpression.And we further verified that overexpression of Bhlhe40 could inhibit the expression of Hdac2,which may be related to the repression of Hdac2 transcription.Conclusion:This study suggests that Bhlhe40 plays a protective role against senescence and oxidative damage in cochlear hair cells exposed to H2O2.

Modulation of copper transporters in protection against cisplatin-induced cochlear hair cell damage

Cisplatin belongs to platinum-based drugs and is widely used in cancer chemotherapy.Ototoxicity is one of the major dose limiting side-effects of cisplatin.For toxicity to occur cisplatin must first be transported from the bloodstream into cochlear cells.Three copper transporters are considered pathways for regulating the uptake and translocation of cisplatin into cells:Ctr1,ATP7A and ATP7B.Our recent study with cochlear organotypic cultures shows that cochlear hair cells can be destroyed by cisplatin at low concentrations from 10μm to 100μn.However,high doses of cisplatin cannot damage hair cells,maybe due to intrinsic feedback reactions that increase export of platinum by ATP7B when the platinum concentration is high in extracellular space.Cimitidine is a specific copper transporter inhibitor that can block the entrance of copper and platinum,and may prevent cisplatin-induced cochlear hair cell injury.To evaluate this hypothesis,we treated cochlear organotypic cultures with cisplatin (10 μm or 50 μm) alone,or cisplatin combined with cimitidine at concentrations ranging from 10-2000 μm for 48 hours.cisplatin at 10 μm damaged about 20% hair cells.In contrast,when cimitidine (10 μm,100 μm and 2000 μm) was added to the culture,near 100% cochlear hair cell survived.At higher concentration (50 μm),cisplatin destroyed about 80% of cochlear hair cells.However,100 μmcimitidine rescued about 50% hair cells from cisplatin damage,and 2000μm cimitidine protected about 80% hair cells.The data of western blot showed that CTR1 and ATP7B expressions were increased in cisplatin treated cochlear tissue,but cimitidine significantly reduced CTR1 and ATP7B.In addition,ATP7A expression was depressed a little after cisplatin treatment.Considering that Ctr1 is involved in copper and platinum influx,but the ATP7A and ATP7B are copper export transporters,the results suggest that cimitidine can effectively block the entrance by copper transporters and stop the influx of cisplatin.

Ephrin A2 protein expression in the regeneration and plasticity of cochlear hair cells in chicken following kanamycin ototoxicity

The results from this study showed that the thresholds of brainstem auditory-evoked potentials peak following 10 successive days of intramuscular injection of Roman chickens with kanamycin, starting 3 days after birth. Fluorescence immunohistochemistry analysis revealed few ganglion cells positively labeled for Ephrin A2 in the cochlea of experimental chickens from 2 days before until 7 days after the last kanamycin injection. The number of Ephrin A2-positive ganglion cell bodies was increased at 15 days after the last injection and was similar to that in normal chickens at 30 days following the cessation of kanamycin treatment. These experimental findings indicate that Ephrin A2 protein expression in the acoustic ganglia is synchronized with the connection damage and regeneration of cochlear hair cells after kanamycin exposure. Ephrin A2 may play an important role in the regeneration and plasticity of cochlear hair cells in the chick cochlea following kanamycin ototoxicity.

Distribution and Functional Characteristics of Voltage-Gated Sodium Channels in Immature Cochlear Hair Cells

Voltage-gated sodium channels(VGSCs)are transiently expressed in cochlear hair cells before hearing onset and play an indispensable role in shaping spontaneous activity.In this study,we showed that Na^+currents shaped the spontaneous action potentials in developing mouse inner hair cells(IHCs)by decreasing the time required for the membrane potential to reach the action-potential threshold.In immature IHCs,we identified 9 known VGSC subtypes(Navl.la-l.9ot),among which Navl.7a was the most highly expressed subtype and the main contributor to Na+currents in developing hair cells.Electrophysiological recordings of two cochlea-specific Navi.7 variants(CbmNavl.7a and CbmNavl.7b)revealed a novel loss-of-function mutation(C934R)at the extracellular linker between segments 5 and 6 of domain II.In addition,post-transcriptional modification events,such as alternative splicing and RNA editing,amended the gating properties and kinetic features of CbmNavl.7a(C934).These results provide molecular and functional characteristics of VGSCs in mammalian IHCs and their contributions to spontaneous physiological activity during cochlear maturation.

电针治疗调节miR-183对噪声性耳聋模型耳蜗毛细胞VEGF表达的影响

目的:探讨电针治疗调节miR-183对噪声性耳聋(NIHL)模型耳蜗毛细胞血管内皮生长因子(VEGF)表达的影响与作用机制。方法:将雄性SD大鼠随机均分为空白对照组、NIHL组、NIHL+针刺组、NIHL+针刺+腺病毒(AAV)-NC组和NIHL+针刺+AAV-sp-miR-183组。针刺组取中渚穴进行刺激。利用AAV载体在NIHL大鼠中敲低miR-183。各组大鼠进行听觉脑干反应(ABR)评估与毛细胞计数。qRT-PCR分析大鼠耳蜗组织miR-183水平。蛋白质免疫印迹测定VEGF水平。结果:与对照组相比,NIHL组耳蜗组织中miR-183的水平降低,ABR阈值差与毛细胞的缺失率升高,耳蜗毛细胞VEGF表达的水平升高(P<0.05)。与NIHL组相比,NIHL+针刺组耳蜗组织中miR-183的水平上升,ABR阈值差与毛细胞的缺失率降低,耳蜗毛细胞VEGF表达的水平升高(P<0.05)。NIHL+针刺+AAV-sp-miR-183组与NIHL+针刺+AAV-NC组相比,miR-183的水平降低,ABR阈值差与毛细胞的缺失率升高,耳蜗毛细胞VEGF表达的水平降低(P<0.05)。结论:电针治疗可以通过上调miR-183进而促进NIHL大鼠耳蜗毛细胞VEGF的表达,降低噪音诱导的NIHL大鼠ABR阈值差增高与毛细胞损伤。

EFFECTS OF DIABETES ON HEARING AND COCHLEAR STRUCTURES

Diabetes mellitus (DM) is a chronic systemic disease characterized by hyperglycemia, with various patho-genic mechanisms. From absolute or relative insulin deficiency, patients with DM often demonstrate vari-ous levels of metabolic disorders. Major clinical manifestations of DM include metabolic disorders, vascu-lar lesions, circulatory disturbances and neurologic complications. Along with advances in DM research, re-ports of DM related tinnitus and hearing impairment have increased continuously. Research on DM related auditory system dysfunction has focused on cochlear microcirculation, cellular homeostasis, genetics and ag-ing. Cochlear microcirculation plays an important role in cochlear physiology and its disorders are associat-ed with many inner ear diseases. Ischemia and subsequent reperfusion seen in cochlear microcirculation dis-orders are important factors in hearing damage. Understanding cochlear microcirculation and structural as well as functional changes in DM patients with hearing loss and their causal factors will help reveal patho-genic mechanisms in diabetic hearing loss and provide new ideas in developing interventions and preventing damages caused by diabetes.

Stem cell-based approaches: Possible route to hearing restoration?

Disabling hearing loss is the most common sensorineural disability worldwide.It affects around 466 million people and its incidence is expected to rise to around 900 million people by 2050,according to World Health Organization estimates.Most cases of hearing impairment are due to the degeneration of hair cells(HCs)in the cochlea,mechano-receptors that transduce incoming sound information into electrical signals that are sent to the brain.Damage to these cells is mainly caused by exposure to aminoglycoside antibiotics and to some anti-cancer drugs such as cisplatin,loud sounds,age,infections and genetic mutations.Hearing deficits may also result from damage to the spiral ganglion neurons that innervate cochlear HCs.Differently from what is observed in avian and nonmammalian species,there is no regeneration of missing sensory cell types in the adult mammalian cochlea,what makes hearing loss an irreversible process.This review summarizes the research that has been conducted with the aim of developing cell-based strategies that lead to sensory cell replacement in the adult cochlea and,ultimately,to hearing restoration.Two main lines of research are discussed,one directed toward the transplantation of exogenous replacement cells into the damaged tissue,and another that aims at reactivating the regenerative potential of putative progenitor cells in the adult inner ear.Results from some of the studies that have been conducted are presented and the advantages and drawbacks of the various approaches discussed.

传出神经对听力发育早期耳蜗放大功能影响的研究

目的利用外毛细胞乙酰胆碱受体α9亚基敲除(Knock-out,Chrna9 KO)与功能获得性敲入(Knockin,Chrna9 KI)的点突变小鼠,重点关注Prestin蛋白水平与耳蜗频率编码方面的差异,研究耳蜗传出神经支配对听力发育的影响。方法选取出生后18 d的KO、KI小鼠与其各自对照组,采用听性脑干反应(auditory brainstem responses,ABR)检测听觉功能;通过耳声发射畸变产物(distortion product otoacoustic emission,DPOAE)群延时实验技术评估基底膜上固定频率的编码位置;通过免疫荧光染色分别观察小鼠的传出神经突触与带状突触;全细胞膜片钳技术测量非线性膜电容来评估外毛细胞的功能及Prestin蛋白的表达情况。结果4.0~45.0 kHz的9个频率中,KO Homo组ABR阈值与KO WT组比较,KI Homo组ABR阈值与KI WT组比较,差异均无统计学意义(P>0.05)。22.6、16.0、8.0 kHz频率的90、85、80 dB SPL处,KI Homo组ABR的Ⅰ波波幅高于KI WT组,差异有统计学意义(P<0.05)。KO Homo组各频率、各刺激声的Ⅰ波波幅与KO WT组比较,差异均无统计学意义(P>0.05)。在13 kHz频率上的60 dB SPL,KI Homo组群延时短于KI WT组,差异有统计学意义(P<0.05)。在各频率上,KO Homo组群延时与KO WT组比较,差异均无统计学意义(P>0.05)。KI Homo组传出神经MOC终末计数顶圈第1、3排外毛细胞多于KI WT组,差异有统计学意义(P<0.05),中、底圈外毛细胞与KI WT组比较,差异无统计学意义(P>0.05)。KO Homo组传出神经MOC终末计数顶、中圈第3排外毛细胞数量少于KO WT组,底圈第3排少于KO WT组,差异均有统计学意义(P<0.05)。KI Homo组、KO Homo组外毛细胞非线性膜电容曲线、Qmax值、Vh值、Clin值、Qsp值与KI WT组、KO WT组比较,差异无统计学意义(P>0.05)。结论在听觉发育早期,传出神经支配末梢数量的降低不影响正常的听觉功能、内毛细胞带状突触与外毛细胞电能动性。然而,传出神经调控功能的增强,在不干扰毛细胞发育的情况下,可能功能性地改变了耳蜗的行波与基底膜频率编码模式。

PTEN inhibitor bisperoxovanadium protects against noise-induced hearing loss

Studies have shown that phosphatase and tensin homolog deleted on chromosome ten(PTEN)participates in the regulation of cochlear hair cell survival.Bisperoxovanadium protects against neurodegeneration by inhibiting PTEN expression.However,whether bisperoxovanadium can protect against noise-induced hearing loss and the underlying mechanism remains unclear.In this study,we established a mouse model of noise-induced hearing loss by exposure to 105 dB sound for 2 hours.We found that PTEN expression was increased in the organ of Corti,including outer hair cells,inner hair cells,and lateral wall tissues.Intraperitoneal administration of bisperoxovanadium decreased the auditory threshold and the loss of cochlear hair cells and inner hair cell ribbons.In addition,noise exposure decreased p-PI3K and p-Akt levels.Bisperoxovanadium preconditioning or PTEN knockdown upregulated the activity of PI3K-Akt.Bisperoxovanadium also prevented H_(2)O_(2)-induced hair cell death by reducing mitochondrial reactive oxygen species generation in cochlear explants.These findings suggest that bisperoxovanadium reduces noise-induced hearing injury and reduces cochlear hair cell loss.

柴胡皂苷A对噪声诱发听力损失小鼠受损毛细胞及氧化应激的影响

【目的】探讨柴胡皂苷A对噪声诱发听力损失小鼠的干预作用及机制。【方法】将45只C57BL/6小鼠随机分为正常组、噪声暴露组、柴胡皂苷A组,每组15只。柴胡皂苷A组接受噪声暴露的同时给予柴胡皂苷A 10.0 g·kg^(-1)·d^(-1)灌胃;噪声暴露组接受噪声暴露,给予等体积生理盐水灌胃;正常组不接受噪声暴露,给予等体积生理盐水灌胃。每日1次灌胃,连续4周。给药结束后,检测小鼠听力脑干反应(ABR),采用Hoechst荧光染色法和扫描电镜分别对应观察耳蜗毛细胞数量、形态,采用8-羟基脱氧鸟苷(8-OHdG)免疫荧光染色法观察耳蜗组织氧化应激损伤情况,Western Blot法检测耳蜗组织4-羟基壬烯醛(4-HNE)及3-硝基酪氨酸(3-NT)表达。【结果】(1)与正常组比较,噪声暴露组小鼠ABR域值明显增加(P<0.001);与噪声暴露组比较,柴胡皂苷A组小鼠ABR域值明显降低(P<0.01)。(2)正常组小鼠耳蜗毛细胞核完整、纤毛排列有序;噪声暴露组耳蜗毛细胞核部分丢失,纤毛出现倾斜、部分破裂;柴胡皂苷A组耳蜗毛细胞核完整性、纤毛形态较噪声暴露组得到明显改善。(3)与正常组比较,噪声暴露组小鼠耳蜗毛细胞中8-OHdG及耳蜗组织4-HNE、3-NT表达水平明显升高(P<0.001);与噪声暴露组比较,柴胡皂苷A组小鼠耳蜗毛细胞中8-OHdG及耳蜗组织4-HNE、3-NT表达水平明显降低(P<0.01)。【结论】柴胡皂苷A可有效干预小鼠噪声性听力损失,其机制与抑制氧化应激、保护耳蜗毛细胞有关。

不同种属实验动物耳蜗毛细胞年龄相关性缺失的不同模式

目的展示自然衰老和耳聋相关基因遗传缺陷之间耳蜗毛细胞缺失的不同模式。方法用不同龄的长尾猴、南美栗鼠、豚鼠、Sprague-Dawley大鼠、CBA/CaJ小鼠、C57BL/6J小鼠、A/J小鼠、DBA/2J小鼠和侏儒灰色突变纯合子(dwg/dwg)小鼠作为受试对象。所有测试动物的耳蜗基底膜都被制作成平坦的耳蜗基底膜铺片。沿着耳蜗基底膜的全长,基底膜上所有的内外毛细胞都被完整计数,毛细胞的计数结果被输入到耳蜗图软件并自动生成每组实验条件的平均耳蜗图。结果在天然衰老的动物中,耳蜗毛细胞的缺失总是发生在老年阶段。与此不同的是,在耳聋相关基因缺陷的动物中,耳蜗毛细胞的缺失却是发生在青年阶段甚至幼年阶段。发生在天然老化动物的耳蜗毛细胞缺失总是呈均匀分布或从耳蜗的顶回向底回扩展。但是,发生在具有耳聋相关基因遗传缺陷动物的耳蜗毛细胞缺失却通常表现为从耳蜗的底回向顶回扩展。结论本实验观察结果表明,发生在天然衰老的不具备耳聋相关基因缺陷动物身上的年龄相关性耳蜗毛细胞缺失反映的是真正由衰老引起的耳蜗退化性病变,而发生在伴有耳聋相关基因遗传缺陷的年幼动物身上的年龄相关性耳蜗毛细胞缺失可能与耳聋相关基因的遗传缺陷有关。

Experimental study of transient cochlear ischemia as a cause of sudden deafness

The etiology of sudden deafness or idiopathic sudden sensorineural hearing loss(ISSHL) remains unclear. Over the past 15 years, we have investigated the mechanisms of ischemic-induced hearing loss using a gerbil model of transient cochlear ischemia. In the gerbil, cochlear ischemia can be induced by occluding the bilateral vertebral arteries simultaneously at the neck, because the posterior communicating arteries of the Circle of Willis close spontaneously around 1 mo after birth. When 15 min ischemia was loaded on this animal, permanent hearing loss of about 25 d B and the death of hair cells, especially inner hair cells were induced. These pathological changes were mainly due to lack of an energy source, glutamate excitotoxicity, and the production of free radicals, especially superoxide and nitrous oxide species. Ischemic damage could be prevented by various procedures, such as cooling the cochlea, intratympanic administration of insulin-like growth factor 1 or AM-111(an anti-apoptotic agent), and systemic administration of prednisolone(steroid), edarabone(free radical scavenger), ginsenoside Rb1(Kanpo), hematopoietic stem cells, glia-cell derived neurotrophic factor, and liposome-encapsulated hemoglobin(artificial red blood cells). We also found that the cochlea was protected by the ischemic tolerance, indi-cating that minor cochlear ischemia alleviates or prevents inner ear damage in subsequent severe cochlear ischemia. As ISSHL usually occurs suddenly, with no preceding sign or symptom, we suggest that most ISSHL cases are caused by circulatory disturbance, probably at the stria vascularis.

Distortion product otoacoustic emissions in newborn babies with and without late-term maternal iron deficiency anaemia

Background:Studies on animals have demonstrated that maternal iron deficiency anaemia(IDA)could result in decreased cochlear sensory hair cells and reduced amplitudes of distortion-product otoacoustic emissions(DPOAEs)of young guinea pigs.Thus,it is essential to study the functioning of cochlear hair cells using DPOAEs in human newborn babies with maternal IDA.The current study explores maternal IDA’s effect on DPOAEs in newborn babies.Method:A total of 110 newborn babies with gestational age≥34 weeks were considered and a‘betweensubjects’design was used.The participants were divided into 3 groups-“Normal”(61 babies without maternal IDA),“Mild”(28 babies with mild maternal IDA)and“Moderate”(21 babies with moderate maternal IDA).The cord blood was collected and the DPOAEs were recorded for each baby for a range of frequencies(1 k 8 kHz)and a range of intensities(7040 dB SPL in 10 dB steps).Results:The analysis of both DP-gram and DP input-output(I/O)function showed that there was no significant difference(p>0.05)across the normal,mild,and moderate groups in the overall presence of DPOAEs as well as the amplitude across frequencies or intensities(7040 dB SPL).Also,the overall correlation of RBC indices with DPOAE amplitude across frequencies as well as the slope of the I/O function showed no relationship.Conclusion:The current study concludes that there is no effect of late-term maternal IDA on the DPOAEs of newborn babies.

Protective effects of the cochlear efferent system on the outer hair cells against intense sound:evidences from DPOAEs

It has been revealed in recent years that contralateral acoustic stimulation can affect cochlear active mechanisms through activating medial olivocochlear system (MOC) of the cochlear efferent nerve fibers. The MOC is therefore postulated to exert protective effects on outer hair cells (OHCs) under intense sound condition. In this study the effects of 4 kHz intense tone exposure on distortion product otoacoustic emissions (DPOAEs) in guinea pigs with and without contralateral white noise stimulation were observed so that to investigate the protective effects of MOC on OHCs. The results showed that DPOAEs obviously deceased after the intense tone exposure in all animals, while both the amplitude reduction and the affected frequency range of DPOAEs were smaller in animals with simultaneously delivered contralateral white noise during the tone exposure than that in animals without colltralateral acoustic stimulation. The above results may suggest some protective nature of the contralateral sound stimulating effects which might be mediated through the activity of MOC. These perhaps can serve as the evidence that the protective mechanism against intense sound operates in the outer hair cells which are strongly innervated by MOC

增龄相关听力丧失小鼠耳蜗毛细胞表型与基因突变的关系

目的 观察增龄相关听力丧失 (AHL)小鼠耳蜗毛细胞病理改变的超微结构 ,为老年性聋病理生理及临床表现+基因表型提供形态学改变依据。方法 应用扫描电镜 (SEM)观察BALB/c小鼠耳蜗Corti器毛细胞的超微结构改变 ,测定动物ABR反应阈值。DNA提取PCR扩增分析基因型。结果 6月龄BALB/c小鼠耳蜗底回内外毛细胞有连续的缺失 ,静纤毛束有融合、散乱、变短和失去劲度。ABR阈值呈中到重度听力损失。证明种系特异的Ahl基因位点和基因功能。结论 耳蜗毛细胞静纤毛束融合、散乱、变短是老年性聋早期的主要病理改变 ,mdfw与Ah1的表现形式是同一基因位点 ,可能与myosin基因突变有关。

2型糖尿病小鼠内质网应激对耳蜗毛细胞退行性变的影响

目的:探讨内质网应激(ERS)对1%链脲佐菌素(STZ)诱导的糖尿病小鼠耳蜗毛细胞退行性变的影响,阐明其作用机制。方法:选取清洁级1月龄雄性昆明小鼠20只,随机分为对照组和模型组,模型组小鼠采用腹腔注射40mg·kg^(-1) STZ建立2型糖尿病模型。尾静脉采血测定小鼠空腹血糖,通过听觉脑干反应(ABR)检测小鼠的ABR阈值,耳声发射测试(OAE)实验检测OAE阈值,应用小鼠耳蜗铺片技术计算小鼠耳蜗外毛细胞的缺损率,采用Western blotting法检测小鼠耳蜗毛细胞中GRP78、caspase-12、p-ERK和Nrf2蛋白表达水平。结果:与对照组比较,第2次注射STZ后7和14d模型组小鼠空腹血糖差异无统计学意义(P>0.05),21、28和35d空腹血糖明显升高(P<0.05),35d达到最高值。与对照组比较,模型组小鼠在8、12和24kHz各个频率的ABR阈值明显升高(P<0.05)。与对照组比较,低频刺激下模型组小鼠OAE阈值无明显变化(P>0.05),在中频和高频刺激下模型组小鼠OAE阈值明显升高(P<0.05)。小鼠耳蜗外毛细胞缺损主要集中在底回端,耳蜗中回和顶回外毛细胞缺损较少;与对照组比较,模型组小鼠耳蜗中的底回外毛细胞缺损率明显升高(P<0.05),中回和顶回外毛细胞缺损率略有升高,但差异无统计学意义(P>0.05)。与对照组比较,模型组小鼠耳蜗毛细胞中GRP78和caspase-12蛋白表达水平升高(P<0.05),p-ERK和Nrf2蛋白表达水平降低(P<0.05)。结论:ERS能够引起糖尿病小鼠耳蜗外毛细胞缺损率和ABR脑干听力阈值升高,并降低p-ERK和Nrf2的蛋白表达水平,提示ERS可促进2型糖尿病小鼠耳蜗毛细胞的退行性病变。

纯中药制剂复聪汤对庆大霉素致聋豚鼠耳蜗毛细胞修复再生的实验研究

目的观察纯中药制剂对庆大霉素致聋动物和耳蜗毛细胞的修复再生作用。方法选用73只健康青年豚鼠,行听力学检查后,53只动物连续肌肉注射庆大霉素(80mg.kg-1.d-1)24～30天致聋(GM组),其间死亡8只,剩余45只随机分成中药治疗组(25只)和致聋后对照组(20只),中药治疗组给予纯中药制剂"复聪汤Ⅰ号"口服液和"复聪汤Ⅱ号"滴耳液治疗,致聋后对照组同法给予生理盐水。另外20只豚鼠作为正常对照组,每天肌肉注射等量生理盐水。在治疗30、60和90天后对GM组两组动物分别行ABR、DPOAE检测,同时,每一时间点处死6只动物,左侧耳蜗行扫描电镜观察,右侧耳蜗铺片行光镜观察和毛细胞计数。结果实验前所有豚鼠的听功能正常;连续注射庆大霉素30天后,GM组豚鼠ABR反应阈值上升到50～80dB SPL,DPOAE幅值降低,光镜和电镜下表现为耳蜗毛细胞纤毛断碎、倒伏、融合和消失,多处毛细胞表皮板肿胀、突起和疱疹样变性,或毛细胞被完全挤出网状板,基底回和第三回耳蜗毛细胞严重消失;中药治疗30天后,80%的耳聋豚鼠的ABR反应阈恢复到30～50dB SPL,DPOAE幅值明显提高;耳蜗铺片和电镜观察显示耳蜗毛细胞数目有一定恢复,组织结构有修复现象,扫描电镜可见再生毛细胞仅出现少量纤毛,而致聋后对照组未发现此种现象;治疗60天后,耳蜗毛细胞数目明显增多,Corti器的毛细胞区有大量的增殖细胞出现,扫描电镜可见成小束的新生纤毛出现在毛细胞缺失部位,同时支持细胞大量增殖;治疗90天后,再生的静纤毛束已基本形成,尤其是耳蜗基底部位的毛细胞明显增多,听功能基本正常。结论纯中药制剂复聪汤对庆大霉素致聋豚鼠耳蜗毛细胞有一定的修复和再生作用。

爆震后豚鼠耳蜗毛细胞和螺旋神经节细胞定量观察

目的 :观察爆震后耳蜗毛细胞和螺旋神经节细胞的变化。 方法 :复制强脉冲噪声致聋豚鼠模型 ,以脑干听觉诱发电位测试仪测定听神经脑干反应 (ABR)阈值 ,通过耳蜗铺片计算机图像分析行毛细胞计数 ,耳蜗病理切片螺旋神经节细胞计数。结果 :正常对照组和噪声暴露后 2 1d的实验组耳蜗钩回、第 1和第 2回毛细胞总数分别为 3 5 99± 15 9.6个 ,6 0 2 2± 98.4个 ;二下螺旋神经节细胞计数分别为 (5 1± 4.72 )个 ,(2 7± 6 .94)个 ,以上均数各组间相差显著。结论 :爆震后不仅 ABR阈值升高 ,毛细胞数减少 。

N-乙酰半胱氨酸对活性氧诱导耳蜗毛细胞凋亡的抑制作用的观察

目的探讨N-乙酰半胱氨酸(N-acetylcysteine,NAC)对活性氧诱导耳蜗毛细胞凋亡的抑制作用。方法选用新生1～5天SD大鼠24只,随机分为4组,每组6只12耳:①无血清培养基组;②0.1mmol/L H2O2组(H2O2组);③10mmol/L N-乙酰半胱氨酸组(NAC组);④10mmol/L NAC+0.1mmol/L H2O2组(NAC+H2O2组)。分离各组动物Corti器,分别放入相应培养液中培养,培养结束后用丫啶橙(YO)/碘化丙啶(PI)双重染色技术检测并计数凋亡毛细胞。结果 NAC组耳蜗基底膜的形态结构与无血清培养基组无明显差异,未见凋亡细胞;H2O2组可见大量凋亡细胞,细胞形态发生改变,出现水肿及碎裂,还有部分细胞缺失;NAC+H2O2组细胞仍保持完好形态,只见少许凋亡细胞。结论抗氧化剂NAC对外源性H2O2诱导的耳蜗毛细胞凋亡有抑制作用。

甲状腺素对豚鼠耳蜗毛细胞的保护作用

应用耳蜗外淋巴灌流技术、微电极技术及扫描、透射电镜技术，观察先服甲状腺素（１０ｍｇ）三次后行外淋巴灌流卡那霉素（１０－３ｇ／ｍｌ）１小时的豚鼠实验组（Ｔ／Ｋ）蜗内电位（ＥＰ），耳蜗微音电位（ＣＭ）和毛细胞的亚微结构变化，并与单纯灌流卡那霉素（１０－３ｇ／ｍｌ）的豚鼠对照组（ＫＭ）进行比较，发现３组动物ＥＰ无明显差异；实验组（Ｔ／Ｋ）的ＣＭ下降较对照组（ＫＭ）少，两者有显著差异；实验组动物外毛细胞损伤较对照组动物轻，提示甲状腺素可能直接作用于听毛细胞，减轻卡那霉素对内耳的毒副作用。