Correlation of PDCD5 and Apoptosis in Hair Cells and Spiral Ganglion Neurons of Different Age of C57BL/6J Mice

This study examined the expression pattern of programmed cell death 5 (PDCD5) in co-chlear hair cells and spiral ganglion neurons (SGNs) and its association with age-related hearing loss in mice.Sixty C57BL/6J (C57) mice at different ages were divided into four groups (3,6,9 or 12 months).PDCD5 expression was detected by using immunohistochemistry,real-time PCR and Western blot.Morphological change of the cochleae was also evaluated by using immunoassay.The results showed that the expression of PDCD5 had a gradual increase with ageing in both protein and RNA levels in C57 mice,as well as gradually increased apoptosis of cochlear hair cells and SGNs.In addition,we also found that caspase-3 activity was enhanced and its expression was enhanced with ageing.It is implied that overexpression of PDCD5 causes the increase in caspase-3 activity and the subsequent increase of apoptosis in cochlear hair cells and SGNs,and thereby plays a role in the pathogenesis of presbycusis.Thus,PDCD5 may be a new target site for the treatment and prevention of age-related hearing loss.

A study of gentamicin injury mechanisms using cultured mouse cochlear spiral ganglion cells

Objective To study gentamicin injury mechanisms using postnatal mouse cochlear spiral gangcells （SGC）. Methods SGCs were isolated using a combinatorial approach of enzymatic digestion and mechanical separation from P2 - 6 Kunming mouse cochleae. After 4 days, cultured SGCs were fixed with 4% paraformaldehyde at room temperature for immunocytochemical examination using the methods of S-P and the monoclonal antibody against mouse neurofilament protein （Neurofilament-68/200Kda, NF-L＋ H）. SGCs were randomly divided into a blank control group and three gentamicin treatment groups （medium gentamicin concentration at 50 mg/L, 100 mg/L and 150 mg/L respectively）, SGCs were collected and examined under a transmission electron microscope after being cultured for 48 h. Results SGC primary culture was successful. SGC cytoplasm and neurites were dyed brownish yellow by the monoelonal mouse neurofilament protein antibody. SGCs showed classical bipolar neuron appearance. Under the transmission electron microscope,.gentamicin treated SGCs showed morphological features different compared to those in the blank control group, which might indicate apoptosis. Conclusion Our results indicate that gentamicin has direct toxic effects on cochlear SGCs in mice and the injury mechanism is closely related with apoptosis. Damage to mitochor, dria may play an important role in the process.

Gene transfection mediated by polyethyleneiminepolyethylene glycol nanocarrier prevents cisplatininduced spiral ganglion cell damage

Polyethyleneimine-polyethylene glycol （PEI-PEG）, a novel nanocarrier, has been used for trans- fection and gene therapy in a variety of cells. In our previous study, we successfully carried out PEI-PEG-mediated gene transfer in spiral ganglion cells. It remains unclear whether PEI-PEG could be used for gene therapy with X-linked inhibitor of apoptosis protein （XIAP） in the inner ear. In the present study, we performed PEI-PEG-mediated XIAP gene transfection in the cochlea of Sprague-Dawley rats, via scala tympani fenestration, before daily cisplatin injections. Audito- ry brainstem reflex tests demonstrated the protective effects of XIAP gene therapy on auditory function. Immunohistochemical staining revealed XIAP protein expression in the cytoplasm of cells in the spiral ganglion, the organ of Corti and the stria vascularis. Reverse transcription-PCR detected high levels of XIAP mRNA expression in the cochlea. The present findings suggest that PEI-PEG nanocarrier-mediated XIAP gene transfection results in XIAP expression in the cochlea, prevents damage to cochlear spiral ganglion cells, and protects hearing.

sRAGE通过AGEs-RAGE信号轴抑制小鼠SGCs的凋亡

目的探讨可溶性RAGE(soluble form of receptor for advanced glycation-end products,sRAGE)对晚期糖基化终产物(advanced glycation end products,AGEs)-晚期糖基化终产物受体(receptor for advanced glycation-end products,RAGE)介导的C57BL/6J小鼠SGCs(spiral ganglion cells,SGCs)凋亡及RAGE受体表达的影响。方法不同浓度的sRAGE作用于培养5天后的螺旋神经节细胞和加入AGEs-BSA作用2 h后的SGCs细胞,采用免疫荧光法鉴定SGCs,通过流式细胞术检测细胞凋亡,以及RT-PCR检测RAGE的mRNA的表达,琼脂糖凝胶电泳对扩增结果进行确认,同时采用western blot技术检测凋亡相关蛋白Bax、BCL-2及caspase-3的表达情况。结果原代培养获得足够数量以及活性良好的SGCs,并用小鼠抗神经微丝蛋白抗体染色以鉴定。单纯向SGCs加入不同浓度的sRAGE,细胞凋亡无明显增加,RAGE受体的表达无明显增多;而不同浓度sRAGE加入AGEs作用的SGCs后,可见SGCs的凋亡随sRAGE浓度增加而减少,呈浓度相关性,RAGE受体的mRNA表达也随之减弱。凋亡相关蛋白中,BCL-2表达升高,Bax及cleaved caspase-3表达降低。结论 s RAGE可以减少AGEs诱导的SGCs的凋亡,并减少膜上RAGE受体的表达,可能与s RAGE竞争性结合AGEs而不产生相应生物学效应有关。

Migration of R28 Retinal Precursor Cells into Cochlear and Vestibular Organs

Damaged hair cells and neurons in the inner ear generally can not be replaced in mammals. The loss of these cells causes permanent functional disorders in both the cochlear and vestibular systems. Transplantation of retinal precursor cells, R28 cells, into inner ear tissue may help replace missing cells. The aim of the current project was to induce R28 cell transdifferentiation into cochlear and vestibular cell types under culture conditions. The first part was related to R28 cell labeling with DiI fluorescence that would help identify and track R28 cells. The second part involved co-culturing R28 cells in cochlear and vestibular organotropic cultures or isolated spiral ganglion neurons. The results suggest that R28 cells have the potential to differentiate into supporting cell types and spiral ganglion neurons in serum free medium, probably under the influence of diffusible signals from inner ear tissues. This information is useful for future efforts in inducing stem cell differentiation in the inner ear to replace lost sensory and neural cells.

Phenotypic differentiation of neonatal rat cochlear spiral ganglion neurons following trypsin dissociation and culture

BACKGROUND： Under laboratory conditions, cochlear spiral ganglion neurons are commonly isolated and cultured by mechanical dissociation. However, these neurons are extremely fragile and survive for only a short time. OBJECTIVE： To establish a trypsin dissociation and culture method for studying neonatal rat cochlear spiral ganglion neurons. DESIGN： A single sample study. SETTING： Department of Otolaryngology, Head and Neck Surgery, Xijing Hospital, Fourth Military Medical University of Chinese PLA. MATERIALS： This study was performed at the central laboratory for Department of Otolaryngology, Head and Neck Surgery, Xijing Hospital, Fourth Military Medical University of Chinese PLA from February to May 2006. A total of 40 neonatal Sprague Dawley rats of either gender, aged 2-5 days, were provided by the Laboratory Animal Center of the Fourth Military Medical University of Chinese PLA. Trypsin and neuronal-specific nuclear protein （NeuN） monoclonal antibodies were purchased from Sigma Company, USA. Culture medium was synthesized using Dulbecco＇s modified Eagle＇s medium （DMEM）/F12 （Gibco Company, USA） supplemented with 10% fetal bovine serum （Sigma Company, USA）, 100 000 U/L penicillin, and 1 mol/L NaOH. The following protocol was performed in accordance with ethical guidelines for the use and care of animals. METHODS： After anesthesia, rats were sacrificed by neck dislocation. A complete cochlear axis with spiral ganglion tissue was removed. The cochlear axis was rinsed three times in a culture dish with a diameter of 35 mm using Hank＇s balanced solution. After washings, the tissue was cut into pieces, digested with 0.25% trypsin for about 20 minutes, and incubated in a 37 ℃ water bath. The tissue was centrifuged, then mixed with serum-containing culture medium. Using a transfer pipette, the cell suspension was transferred to polylysine （0.1%）-treated culture dishes with a diameter of 35 mm. The culture dish was incubated at 37 ℃, with a 5% CO2-air environment. Once the cells adhered to the culture dish wall, DMEM/F12 supplemented with 10% fetal bovine serum was added. MAIN OUTCOME MEASURE： Using an inverted microscope, the adherent cultured cells were observed and neurite growth index was calculated. Immunocytochemistry was performed to identify the spiral ganglion neurons, and NeuN-positive cells were analyzed. Following immunofluorescence, cochlear spiral ganglion neurons were identified through a microscope. RESULTS： Observation of cellular morphology： after digestion, inoculated cells exhibited were spherical, well stacked, and had a transparent appearance. Six hours later, some cells adhered to the culture dish wall, and small neurites were detected in a small number of cells. Twelve hours later, the adherent cells developed into polarized cells. Eighteen hours after inoculation, the adherent cells presented an ellipsoidal appearance, clear cell membranes, homogeneous cytoplasm, good refraction, and a transparent cell body surrounded by a marked halation. Twenty-four hours later, most of the cochlear spiral ganglion neurons exhibited a bipolar neuronal morphology with neurite length ranging from 2-5 times the length of a cell body. Some cochlear spiral ganglion neurons exhibited a tripolar neuronal morphology with neurites that stretched in three directions; neurite length was several times greater than the transverse diameter. Forty-eight to seventy-two hours later, the cells further differentiated and exhibited interwoven neurites, with a length that was 7-8 times greater than the cell body length. Seven days later, cells began to degenerate and underwent apoptosis. Identification of cochlear spiral ganglion neurons： immunocytochemical staining revealed whole cochlear spiral ganglion neurons that were green-colored and exhibited an ellipsoidal cell body with clear neurites. Measurement of neurite growth index： neurite growth index was 0.52±0.13, 0.86±0.21, 1.22±0.33, and 1.05 ±0.26 for 24, 48, 72, and 120 hours after inoculation, respectively. CONCLUSION： Under cell culture conditions of serum and trypsin dissociation, neonatal rat cochlear spiral ganglion neurons grow well, survive for long periods in vitro, and exhibit normal phenotypic differentiation.

Basic flbroblast growth factor protects auditory neurons and hair cells from noise exposure and glutamate neurotoxicity

The purpose of the present study was to determine protectivie effects of basic fibroblast growth factor (bFGF) on cochlear neurons and hair cells in vitro and in vivo. In experiment I, cultured spiral ganglion neurons (SGNs) prepared from P3 mice were exposed to 20mM glutamate for 2 hours before the culture medium was replaced with fresh medium containing 0, 25, 50, and 100 ng/ml bFGF, respectively. Fourteen days later, all cultures were fixed with 4% paraformaldehyde, and stained with 1% toluidine blue. The number of surviving SGNs were counted and the length of SGNs neurites were measured. Exposure to 20 mM glutamate for 24 hours resulted in an inhibition on neurite outgrowth of SGNs and elevated cell death. Treatment of the cultures with bFGF led to promotion of neurite outgrowth and elevated number of surviving SGNs. Effects of bFGF were dose dependent with the highest potency at 100 ng/ml. In experiment Ⅱ, in vivo studies were carried out with guinea pigs in which bFGF or artificial perilymph was perfused into the cochlea to assess possible protective effects of bFGF on cochlear hair cells and compound action potentials(CAP). The CAPs were measured before, immediatly and 48 hours after exposure to noise. Significant differences in CAP were observed (p＜0. 05 ) among the bFGF perfused group, control group(t =3. 896 ) and artificial perilymph perfused group (t =2. 520) at 48 hours after noise exposure, Cochleae were removed and hair cell Loss was analyzed in surface preparations prepared from all experimental animals. Acoustic trauma caused loss of 651 and 687 inner hair cells in the control and artificial perilymph perfused group, respectively. In sharp contrast, only 31 inner hair cells were lost in the bFGF perfused ears. Similarly, more outer hair cells died in the control and perilymph perfuesed group (41830 and 41968, respectively) than in the group treated with bFGF (34258). Our results demonstrate that bFGF protected SGNs against glutmate neurotoxicity in vitro. In addition, treatment with bFGF also protected hair cells from acoustic trauma.

红景天苷改善顺铂引起的小鼠耳蜗毛细胞和螺旋神经节神经元损伤的机制

目的探究红景天苷(SAL)改善顺铂(CIS)引起的耳蜗毛细胞(CHC)和螺旋神经节神经元(SGN)损伤的作用及其与环磷腺苷(cAMP)/蛋白激酶A(PKA)/cAMP效应元件结合蛋白(CREB)通路的关系。方法分离新生C57BL/6小鼠的耳蜗基底膜,分为对照组(C组)、CIS组、SAL组、SAL+SQ22536(cAMP抑制剂)组和SAL+H-89(PKA抑制剂)组,每组20条。C组仅加入无血清BME培养液;CIS组在培养液中加入15μmol/L CIS;SAL组在CIS组基础上加入5μmol/L SAL;SAL+SQ22536组在CIS组基础上加入5μmol/L SAL和5μmol/L SQ22536;SAL+H-89组在CIS组基础上加入5μmol/L SAL和30μmol/L H-89。各组在培养箱中孵育48 h后,免疫荧光染色观察各组CHC和SGN损伤;试剂盒检测各组耳蜗基底膜中ROS和cAMP含量;Western blot检测各组PKA、p-CREB、CREB、Bcl-2、BDNF、NF-M蛋白水平。结果CIS组CHC排列混乱、体积肿大,SGN细胞核破碎、神经突缺失,SAL可减轻CHC和SGNs损伤。与C组相比,CIS组CHC、SGN数量较少(P<0.05),ROS、cAMP含量、PKA、BDNF、NF-M、Bcl-2蛋白及p-CREB/CREB水平较高(P<0.05);与CIS组相比,SAL组CHC、SGN数量较多(P<0.05),ROS含量较低(P<0.05),cAMP含量、PKA、BDNF、NF-M、Bcl-2蛋白及p-CREB/CREB水平较高(P<0.05)。SQ22536和H-89均可逆转SAL对CHC和SGN的保护作用。结论SAL可能通过激活cAMP/PKA/CREB通路,促进抗凋亡蛋白和神经保护因子表达,缓解CIS引起的CHC和SGN损伤。

Recent advances in the application of MXenes for neural tissue engineering and regeneration

Transition metal carbides and nitrides(MXenes)are crystal nanomaterials with a number of surface functional groups such as fluorine,hydroxyl,and oxygen,which can be used as carriers for proteins and drugs.MXenes have excellent biocompatibility,electrical conductivity,surface hydrophilicity,mechanical properties and easy surface modification.However,at present,the stability of most MXenes needs to be improved,and more synthesis methods need to be explored.MXenes are good substrates for nerve cell regeneration and nerve reconstruction,which have broad application prospects in the repair of nervous system injury.Regarding the application of MXenes in neuroscience,mainly at the cellular level,the long-term in vivo biosafety and effects also need to be further explored.This review focuses on the progress of using MXenes in nerve regeneration over the last few years;discussing preparation of MXenes and their biocompatibility with different cells as well as the regulation by MXenes of nerve cell regeneration in two-dimensional and three-dimensional environments in vitro.MXenes have great potential in regulating the proliferation,differentiation,and maturation of nerve cells and in promoting regeneration and recovery after nerve injury.In addition,this review also presents the main challenges during optimization processes,such as the preparation of stable MXenes and long-term in vivo biosafety,and further discusses future directions in neural tissue engineering.

基于自噬途径探讨银杏叶提取物对老年性聋大鼠的保护作用

目的探讨银杏叶提取物对老年性聋大鼠听功能、耳蜗组织形态学和自噬相关蛋白表达的作用。方法将45只大鼠随机分为对照组、模型组和银杏叶提取物低、中、高剂量组(10、20、30 mg/kg),每组9只,采用腹腔注射500 mg/kg D-半乳糖(D-gal)构建老年性聋模型。给药8周后,听性脑干诱发电位(ABR)检测大鼠听阈变化,HE染色观察耳蜗毛细胞、血管纹和螺旋神经节细胞形态变化,免疫荧光染色法检测耳蜗内外毛细胞数量变化,透射电子显微镜观察耳蜗毛细胞超微结构变化,Western blot法检测耳蜗组织中自噬相关蛋白表达。结果与对照组比较,模型组ABR阈值升高(P<0.01),耳蜗内外毛细胞、螺旋神经节细胞和血管纹损伤严重,血管纹厚度、螺旋神经节细胞数、内外毛细胞数和自噬小体数均降低(P<0.01),耳蜗组织Beclin1、LC3Ⅱ蛋白表达和LC3Ⅱ/LC3Ⅰ比值均降低(P<0.01),P62蛋白表达升高(P<0.01);与模型组比较,银杏叶提取物中、高剂量组ABR阈值均降低(P<0.01),耳蜗内外毛细胞及血管纹形态改善,螺旋神经节细胞形态趋向正常,血管纹厚度、螺旋神经节细胞数、内外毛细胞数和自噬小体数均增加(P<0.05,P<0.01),耳蜗组织Beclin1、LC3Ⅱ蛋白表达和LC3Ⅱ/LC3Ⅰ比值均升高(P<0.01),P62蛋白表达降低(P<0.01)。结论银杏叶提取物对老年性聋大鼠的听功能和耳蜗细胞具有保护作用,其机制可能与上调耳蜗组织Beclin1、LC3Ⅱ蛋白表达,下调P62蛋白表达有关。

Injury and protection of spiral ganglion neurons

Cochlear spiral ganglion neurons(SGNs)are bipolar ganglion cells and are the first neurons in the auditory transduction pathway.They transmit complex acoustic information from hair cells to second-order sensory neurons in the cochlear nucleus for sound processing.Injury to SGNs causes largely irreversible hearing impairment because these neurons are highly differentiated cells and cannot regenerate,making treatment of sensorineural hearing loss(SNHL)arising from SGN injury difficult.When exposed to ototoxic drugs or damaging levels of noise or when there is loss of neurotrophic factors(NTFs),aging,and presence of other factors,SGNs can be irreversibly damaged,resulting in SNHL.It has been found that NTFs and stem cells can induce regeneration among dead spiral ganglion cells.In this paper,we summarized the present knowledge regarding injury,protection,and regeneration of SGNs.

当归芍药散调控IKK/IκBα/NF-κB通路对老年性聋小鼠耳蜗螺旋神经节细胞凋亡的影响

目的探究当归芍药散调控核转录因子-κB抑制蛋白激酶(IKK)/核因子κB抑制蛋白(IκBα)/核因子-κB(NF-κB)通路对老年性聋小鼠耳蜗螺旋神经节细胞凋亡的影响。方法将48只C57BL/6J小鼠随机分为老年性聋模型组(Model组)、低剂量当归芍药散组(中药-L组,3.2 g/kg生药)、高剂量当归芍药散组(中药-H组,6.4 g/kg生药)和高剂量当归芍药散+IKK/IκBα/NF-κB信号通路激活剂白藜芦醇(RES)组(中药-H+RES组,6.4 g/kg生药+43.33 mg/kg RES),每组12只小鼠;取12只2月龄的C57BL/6J小鼠作为对照组(Control组)。采用听性脑干反应(ABR)检测各组小鼠听阈值;HE染色观察小鼠耳蜗螺旋神经节的病理变化,并对小鼠耳蜗中回与底回的螺旋神经节细胞的数量进行计数;TUNEL染色法检测小鼠耳蜗螺旋神经节细胞的凋亡。ELISA法检测小鼠耳蜗组织中丙二醛(MDA)与超氧化物歧化酶(SOD)水平。qRT-PCR法检测小鼠耳蜗组织中IL-1β、IL-6与TNF-αmRNA水平。Western blot法检测小鼠耳蜗组织IKK/IκBα/NF-κB通路与凋亡相关蛋白的表达。结果Model组小鼠较Control组小鼠8 kHz、16 kHz、24 kH、32 kHz听阈值、耳蜗螺旋神经节组织TUNEL阳性细胞数、耳蜗组织MDA及IL-1β、IL-6与TNF-αmRNA水平、p-IκBα、凋亡蛋白(Bax、cleaved-Caspase-3)表达水平、IKK、NF-κB p65磷酸化水平均显著升高(均P<0.05),耳蜗螺旋神经节细胞数量、SOD水平、IκBα蛋白表达水平显著降低(均P<0.05),耳蜗螺旋神经节细胞的形态异常、排列疏松紊乱,发生空泡化,出现病理学损伤。中药-L组、中药-H组小鼠较Model组相应指标变化程度较轻(均P<0.05)。RES减弱了当归芍药散对老年性聋小鼠耳蜗螺旋神经节细胞凋亡的抑制作用。结论当归芍药散可能通过下调IKK/IκBα/NF-κB通路抑制老年性聋小鼠耳蜗螺旋神经节细胞凋亡。

Cochlear function after selective spiral ganglion cells degeneration induced by ouabain

Background Ouabain, a cardiac glycoside that specifically binds to Na/K-ATPase and inhibits its activity, was applied to gerbils to develop a method for studying auditory neuropathy. Methods Ouabain was applied to the round window of the cochlea in each gerbil by using a piece of gelfoam with 3 μl or 24 μl （1 mmol/L） ouabain solution. The changes of the threshold of auditory brainstem response, cochlear function round window electrocochleography, as well as the morphological changes of the spiral ganglion cells of the cochlea were observed after application of ouabain for 24 hours or 96 hours. Results In ouabain treated gerbils, auditory brainstem response and compound action potential thresholds showed either elevation or no response at all. However, the thresholds of cochlear microphonic and distortion product otoacoustic emissions were not affected. Degeneration and necrosis of some spiral ganglion cells in ears with applications of ouabain （24 hours, 3 μl, 1 mmol/L; 96 hours, 24 μl, 1 mmol/L ouabain）. The number of spiral ganglion cells was decreased （24 hours, 3 μl, 1 mmol/L ouabain） or near to a total loss （96 hours, 24 μl, 1 mmol/L ouabain）.Conclusions These results indicate a high degree of independence between the spiral ganglion ceils and the outer hair cell systems in the cochlear transduction mechanism. The method used in this study would provide a valuable tool for studying auditory neuropathy.

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.

大鼠螺旋神经节干细胞体外优化培养方法的研究

目的探索贴壁法进行螺旋神经节(Spiral Ganglion,SG)干细胞培养,同时与传统悬浮培养法对比培养的SG干细胞形态、增殖效率及分化表型。方法取新生1天SD大鼠耳蜗的螺旋神经节位置,以悬浮和单层贴壁的方式进行培养,观察SG干细胞的形态学特点。通过活/死细胞染色和Annexin-V/PI双染法比较其生长状态。通过Nestin、Sox2、Ki67等免疫荧光染色及生长曲线测定等方法对其增殖能力进行比较分析。体外胎牛血清诱导SG干细胞分化,通过Tuj1免疫荧光染色鉴定分化表型并比较分化效率。结果两种培养方式均可获得状态良好的高纯度SG干细胞,免疫荧光染色和生长曲线测定结果提示贴壁培养的干细胞的增殖活性较悬浮培养的干细胞更强。诱导分化后,两种培养方式获得的SG干细胞均可分化为Tuj1染色阳性的双极神经元样细胞。结论本研究结果表明单层贴壁可培养出状态良好的SG干细胞,并且其增殖能力较悬浮培养的干细胞更强。贴壁培养的干细胞可被可成功诱导分化为神经元。提示单层贴壁方式可作为一种稳定的SG干细胞培养方法,从而为SG干细胞的相关研究提供重要技术支持。

老年性耳聋病因及分子机制的研究进展

老年性耳聋是老年人群中最常见的感觉缺陷之一,又称为年龄相关性听力损失,是老年人最普遍的感觉缺陷。随着社会逐渐老龄化,老年性耳聋的发病率越来越高。老年性耳聋严重影响了老年人的身心健康,导致老年人的生活质量下降、认知能力改变、社交孤立以及抑郁、沟通障碍等。研究其病因及发病机制对老年性耳聋的诊断、治疗和预防具有重要意义。本综述总结了老年性耳聋分子机制、致病因素、病理分型、治疗手段等。

Inhibition of histone methyltransferase PRMT5 attenuates cisplatininduced hearing loss through the PI3K/Akt-mediated mitochondrial apoptotic pathway

This study aimed to evaluate the therapeutic potential of inhibiting protein arginine methyltransferase 5(PRMT5)in cisplatin-induced hearing loss.The effects of PRMT5 inhibition on cisplatin-induced auditory injury were determined using immunohistochemistry,apoptosis assays,and auditory brainstem response.The mechanism of PRMT5 inhibition on hair cell survival was assessed using RNA-seq and Cleavage Under Targets and Tagment-quantitative polymerase chain reaction(CUT&Tag-qPCR)analyses in the HEI-OC1 cell line.Pharmacological inhibition of PRMT5 significantly alleviated cisplatin-induced damage to hair cells and spiral ganglion neurons in the cochlea and decreased apoptosis by protecting mitochondrial function and preventing the accumulation of reactive oxygen species.CUT&Tag-qPCR analysis demonstrated that inhibition of PRMT5 in HEI-OC1 cells reduced the accumulation of H4R3me2s/H3R8me2s marks at the promoter region of the Pik3ca gene,thus activating the expression of Pik3ca.These findings suggest that PRMT5 inhibitors have strong potential as agents against cisplatininduced ototoxicity and can lay the foundation for further research on treatment strategies of hearing loss.

新生大鼠螺旋神经节细胞体外生长特点及脂质体介导的转染效率

目的探讨螺旋神经节细胞（spiral ganglion cells,SGCs）体外生长规律及特点,并观察阳离子脂质体转染SGCs的情况。方法从出生3~4 d的SD大鼠耳蜗中分离螺旋神经节组织,消化后放在含10%胎牛血清的DMEM/F12中培养,第2 d换用含2%B27及5μmol/L阿糖胞苷的Neurobasal培养基纯化SGCs,取第4 d活性良好的细胞爬片后,通过免疫荧光法用NF-200抗体鉴定SGCs;另外用质粒pEGFP-C2联合Lipofectamine 2000转染SGCs,观察其转染效率及对细胞活性的影响。结果体外培养的SGCs胞体饱满透亮,折光性好,一般能存活2周左右,第3~7 d活性最好。细胞对NF-200染色阳性;约10%的SGCs能被Lipofectamine 2000转染,但小部分细胞轴突缩短,甚至漂浮起来。结论含B27的Neurobasal培养基能培养出活性良好的SGCs;脂质体和质粒pEGFP-C2能成功地转染SGCs,但转染效率较低,并在一定程度上影响细胞的活性。

神经生长因子在小鼠耳蜗中的表达分布及年龄相关性变化

目的探讨神经生长因子(NGF)在小鼠耳蜗中的表达分布与年龄的相关性变化。方法选取5、7月龄的快速老化小鼠亚系8(SAMP8)作为实验组,而同龄抗快速老化小鼠亚系1(SAMR1)作为对照组。分别观察其耳蜗中NGF免疫组化染色及增龄性变化情况。结果在小鼠耳蜗中,NGF在螺旋神经节细胞、内外毛细胞、听神经纤维及血管纹中均有表达,且螺旋神经节细胞及内外毛细胞为主要表达部位。耳蜗螺旋神经节细胞及内外毛细胞NGF免疫组化染色平均光密度值:NGF蛋白在不同月龄快速老化小鼠耳蜗组织中螺旋神经节细胞及毛细胞均有表达,第5、7月龄SAMP8小鼠耳蜗螺旋神经节细胞及毛细胞中的NGF蛋白表达较同龄SAMR1小鼠明显降低(P<0.05)。结论 NGF蛋白在小鼠耳蜗中有表达并且表达水平随着小鼠年龄增长而降低,说明NGF蛋白可能与维持耳蜗的功能状态有关。

耳蜗毛细胞和螺旋神经节及其神经纤维的联合定量观察

目的：将耳蜗基底膜取材技术与耳蜗切片技术相结合以观察同一耳蜗中几个主要结构在病理发展中的相互关系。方法：耳蜗铺片用于定量观察毛细胞，骨性螺旋板切片用于定量观察缰孔内的神经纤维，中轴切片用于定量观察螺旋神经节。结果：将卡铂耳中毒灰鼠的耳蜗标本与正常灰鼠进行比较，显示内毛细胞，神经纤维和螺旋神经节的损失百分比基本一致。结论：卡铂对内毛细胞，神经纤维和螺旋神经节都有破坏作用，至于在卡铂病变早期，究竟哪一部分对损伤更敏感，有待进一步研究。