Inner ear barriers to nanomedicine-augmented drug delivery and imaging

There are several challenges to inner ear drug delivery and imaging due to the existence of tight biological barriers to the target structure and the dense bone surrounding it. Advances in imaging and nanomedicine may provide knowledge for overcoming the existing limitations to both the diagnosis and treatment of inner ear diseases. Novel techniques have improved the efficacy of drug delivery and targeting to the inner ear, as well as the quality and accuracy of imaging this structure. In this review, we will describe the pathways and biological barriers of the inner ear regarding drug delivery, the beneficial applications and limitations of the imaging techniques available for inner ear research, the behavior of engineered nanomaterials in inner ear applications, and future perspectives for nanomedicine-based inner ear imaging.

Dexamethasone does not affect endolymphatic hydrops(EH)in patients with Meniere's disease within 24 h,and intratympanic administration of gadolinium plus dexamethasone simplifies high-quality imaging of EH using a novel protocol of 7 min

Background:Intratympanic administration of gadolinium chelate allows for a better visualization of endolymphatic hydrops(EH)using MRI than intravenous injection and was recently further improved to facilitate high-quality imaging of EH in 7 min.The aim of the present study was to simplify the intratympanic administration protocol by mixing gadolinium chelate with therapeutic dexamethasone and to evaluate the effects of this mixture on the visualization of EH in MRI.Materials and methods:In an in vitro study,the potential impact of gadolinium-diethylenetriamine pentaacetic acid(Gd-DTPA)on the stability of dexamethasone was evaluated by analyzing dynamic changes in dexamethasone with high-performance liquid chromatography(HPLC)after mixing with GdDTPA.Ten patients with definite Meniere's disease(MD)were recruited to study the potential interference of dexamethasone on MRI visualization of EH,and 49 patients with MD were recruited to evaluate the effect of intratympanic injection of Gd-DTPA mixed with dexamethasone on MRI of EH using a 3T MR machine and a novel heavily T2-weighted 3-dimensional fluid-attenuated inversion recovery reconstructed using a magnitude plus zero-filled interpolation(hT2FLAIR-MZFI)sequence.Results:The retention times and peak area of dexamethasone in HPLC were not modified by the addition of Gd-DTPA.EH grading in the cochlea and vestibule was not influenced in any ear by intratympanic injection of dexamethasone.Excellent inner ear images were obtained from all patients,and EHs with various grades were displayed.There were significant correlations between diagnosis and cochlear EH(p<0.01,Spearman's Rho),between diagnosis and vestibular EH(p<0.01,Spearman's Rho),and between cochlear and vestibular EH(p<0.01,Spearman's Rho).The distribution of Gd-DTPA plus dexamethasone negatively correlated with the grade of vestibular EH.Injury of the endolymph-perilymph barrier was detected in one cochlea and three vestibules of 59 inner ears with MD.Conclusions:Intratympanic administration of Gd-DTPA plus dexamethasone yielded high-quality MRI images of EH in patients with MD using a novel 7-min protocol and simplified the clinical application.Intratympanic administration of Gd-DTPA plus dexamethasone might be used to test its therapeutic effect in future work.

Label-free visualization of cholesteatoma in the mastoid and tympanic membrane using CARS microscopy

Objective:The present study aimed to evaluate the possibility of using coherent anti-Stokes Raman spectroscopy（CARS） microscopy to determine the specific molecular morphology of cholesteatoma by detecting the natural vibrational contrast of the chemical bonds without any staining.Materials and methods:Specimens from the mastoid and tympanic membrane with and without cholesteatoma were analyzed using CARS microscopy,two-photon excited fluorescence（TPEF） microscopy,and the second harmonic generation（SHG） microscopy.Results:In cholesteatoma tissues from the mastoid,a strong resonant signal at 2845 cm;was observed by CARS,which indicated the detection of the CH;hydro-carbon lipid bonds that do not generate visible signals at 2940 cm;suggestive of CH;bonds in amino acids.A strong resonant signal at 2940 cm;appeared in an area of the same specimen,which also generated abundant signals by TPEF and SHG microscopy at 817 nm,which was suggestive of collagen.In the tympanic membrane specimen with cholesteatoma,a strong resonant signal with corrugated morphology was detected,which indicated the presence of lipids.A strong signal was detected in the tympanic membrane with chronic otitis media using TPEF/SHG at 817 nm,which indicated collagen enrichment.The CARS and TPEF/SHG images were in accordance with the histology results.Conclusion:These results suggest the need to develop a novel CARS microendoscope that can be used in combination with TPEF/SHG to distinguish cholesteatoma from inflammatory tissues.

Postaurical injection is a systemic delivery supported by symmetric distribution of Gd-DOTA in both the ipsilateral and contralateral ears

Postaurical injection of therapeutics was recently applied in clinical practice to treat inner ear diseases based on supposed existence of a direct channel from the postaurical area to the inner ear. Doubting on the associated reports and aiming to provide evidence on the inner ear uptake mechanism, the present study tracked the dynamic distribution of gadolinium-tetra-azacyclo-dodecane-tetra-acetic acid (Gd-DOTA) in rat inner ears after postaurical injection using MRI. A targeted tympanic medial wall delivery was utilized as control. The results showed that, at the early time points after postaurical injection, Gd-DOTA distributed mainly in tissues surrounding the bulla, temporal bone and skull and neck space. In the inner ear, there was gradual uptake of Gd-DOTA on both the ipsilateral and contralateral sides with equal signal intensities. There was no sign of direct channel carrying the agent from the postaurical area to the inner ear. Targeted tympanic medial wall delivery induced significantly greater uptake of Gd-DOTA in the inner ear than did postaurical injection. At 30 min post-administration, targeted tympanic medial wall delivery yielded 4.6-folds higher signal intensity than did postaurical injection. The total dose of Gd-DOTA delivered by the targeted tympanic medial wall approach was only 0.1% of that delivered by postaurical injection. In conclusion, postaurical injection is a systemic administration, which is similar to hypodermic injection, rather than a focal delivery method. By contraries, targeted tympanic medial wall delivery induces fast and abundant uptake of Gd-DOTA in the ipsilateral inner ear without significant distribution in unwanted areas.

Endolymphatic hydrops in Meniere's disease secondary to otitis media and visualized by gadolinium-enhanced magnetic resonance imaging

Aimed to test the hypothesis that endolymphatic hydrops in Meniere's disease(MD) may be secondary to otitis media, history of a patient who developed MD as a complication of otitis media was reviewed. The inner ear was imaged using a 3.0 Tesla MR system post-intravenous injection of gadolinium-tetraazacyclododecane-tetraacetic acid(Gd-DOTA) in a standard single dosage(0.1 mmol/kg). Both t2-spc-rst-tra-iso(T2-weighted) and heavily T2-weighted 3-dimensional fluid-attenuated inversion recovery magnetic resonance imaging [h T(2)W-3D-FLAIR] sequences were applied. As a result, in the T2-weighted images, the perilymph and endolymph, cerebrospinal fluid surrounding the eighth nerve(N8), and middle ear granulation tissue showed intense signals. In the h T(2)W-3D-FLAIR images, evident enhancement by Gd-DOTA was observed in the middle ear cavity and the perilymphatic compartments of the cochlea. Cochlear endolymphatic hydrops was implicated by the enlarged scala media in the basalturn. In general, the Gd-DOTA uptake in the vestibule was weak, and signs of vestibular endolymphatic hydrops were obvious. The N8 on the diseased side was also significantly enhanced. To conclude, endolymphatic hydrops in MD may be induced by otitis media. Cochlear endolymphatic hydrops in MD secondary to otitis media may not follow the classical pattern.

MEFV,IRF8,ADA,PEPD,and NBAS gene variants and elevated serum cytokines in a patient with unilateral sporadic Meniere's disease and vascular congestion over the endolymphatic sac

The etiology and underlying mechanism of Meniere's disease(MD)development are still unknown,although inflammation and autoimmunity have been implicated as underlying mechanisms.The human endolymphatic sac(ES)has been reported to have innate and adaptive immune capacity in local immune reactions.In vivo demonstration of inflammation of the ES in patients with MD is missing in the literature.We report the case of a 47-year-old female patient diagnosed with unilateral MD with genetic variants and cytokine markers indicating inflammation and vascular congestion of the ES.Endolymphatic hydrops in the right cochlea(grade 2)and vestibulum(grade 3)were detected using MRI.She carried heterozygous variants in MEFV(c.442G>C),IRF8(c.1157G>T),ADA(c.445C>T),PEPD(c.151G>A),NBAS(c.4049T>C),CSF2RB(c.2222C>T),HPS6(c.277G>T),IL2RB(c.1109C>T),IL12RB1(c.1384G>T),IL17RC(c.260_271del GCAAGAGC TGGG),LIG1(c.746G>A),RAG1(c.650C>A),and SLX4(c.1258G>C,c.5072A>G).In the serum,the levels of granulocyte colony-stimulating factor(G-CSF),macrophage inflammatory protein 1a,and IL7 were significantly elevated,and the level of IL2Ra was reduced.Intratympanic administration of dexamethasone temporarily alleviated her hearing loss.Her vertigo was significantly relieved but remained slight after ES administration of corticosteroids.

圆窗和卵圆窗加固术治疗外伤性上半规管骨折

目的探讨圆窗和卵圆窗加固术治疗外伤性上半规管骨折引发的前庭功能障碍的手术方法及效果。方法回顾性分析1例采用圆窗和卵圆窗加固术治疗的外伤性上半规管骨折患者的临床资料,讨论其诊断要点、治疗方法及疗效。结果患者头部外伤后出现低频声诱发眩晕、耳闷、自声增强、不能忍受低频振动等前庭功能障碍症状及听力减退;颞骨高分辨率CT示左侧上半规管顶壁多发性骨折,右侧上半规管壁单发骨折;诊断为上半规管骨折。在局麻下,耳内切口探查鼓室,用腹壁脂肪填塞圆窗,颞肌筋膜覆盖圆窗脂肪及镫骨底板周围,纤维蛋白组织胶密封颞肌筋膜与鼓室粘膜连接处;用钛质部分听骨链移植假体重建听骨链。术后患者立即体会到头部向上冲的感觉,声音诱发眩晕、耳闷、自声增强、耳鸣症状消失;左侧头部知觉恢复正常,右侧头部知觉部分恢复,听力提高,视觉定位好,视物清晰。术后14天左侧4kHz骨导听阈恢复20dB,但全频气骨导差较术前增大。结论微创的圆窗和卵圆窗加固术对撞击伤导致的上半规管裂综合症治疗效果明显。

Clinically relevant human temporal bone measurements using novel high-resolution cone-beam CT

Objective: To test the feasibility of measuring fine temporal bone structures using a newly established cone-beam computed tomography(CBCT)system.Materials and methods: Six formalin-fixed human cadaver temporal bones were imaged using a high-resolution CBCT system that has 900 frames and copper t aluminum filtration. Fine temporal bone structures, including those of the facial nerve canal and vestibular structures, were identified and measured.Results: The fine structures of the middle ear, including the tympanic membrane, tendon of the tensor tympani, cochleariform process of the semicanal of the tensor tympani, pyramidal eminence, footplate of the stapes, full path of the facial nerve within the temporal bone, supralabyrinthine space, semicircular canals, pathway of the subarcuate canal, and full path of the vestibular aqueduct, were clearly demonstrated. The vestibular aqueduct has a midpoint width of 0.4 ± 0.0 mm and opercular width of 0.5 ± 0.1 mm(mean ± SD). The length of the internal acoustic meatus was 10.6 ± 1.2 mm(mean ± SD), and the diameter of the internal acoustic meatus was 3.7 ± 0.3 mm(mean ± SD).Conclusion: This novel high-resolution CBCT system has potentially broad applications in the diagnosis of inner ear disease and in monitoring associated pathological changes, surgical planning, navigation for the ear surgery, and temporal bone training.

低频旋转乳突振动对正常志愿者听力的影响

目的我们设计了一种新颖的治疗眩晕低频旋转乳突振动设备,本研究是为了评估该设备对听觉系统的安全性。方法选12名无眩晕主诉的志愿者,男性10例,女性2例,年龄23-25岁。将低频振动投放于右侧乳突,分别于振动前、振动后0.5小时、7天、和1年行纯音听阈检测,分析比较双耳的不同频率气、骨导阈值的变化。结果受试者双耳在低频振动后0.5小时的,右耳(暴露耳)在0.25、0.5、1.0 kHz骨导听阈分别降低了3、5、3 d B,有显著性差异(p<0.05),气导阈移无显著性差异;振动后7天,左耳(对照耳)在0.25、0.5 kHz气导听阈分别提高了3、2 dB,有显著性差异(p<0.05);振动后1年右耳在0.25、0.5、8kHz气导听阈分别降低了6、6、9 dB,在0.25、0.5、1 kHz骨导听阈分别升高了7、3、4 dB,均有显著性差异(p<0.05),左耳在2、4、8 kHz气导听阈分别提高了6、6、10 dB,在0.25、0.5、1、2、4kHz骨导听阈分别升高了7、6、6、8、8 dB,均有显著性差异(p<0.05)。结论振动后0.5小时及7天的听阈变化无规律,且数值小,无临床意义;1年后的左耳听阈升高6-10 dB,右耳低频气导听阈降低,低频骨导听阈提高,不符合振动引起的特异性改变,因此,该治疗眩晕的低频乳突振动设备对听觉系统是安全的。

Nanoparticle based inner ear therapy

Synthetic nanoparticles can be used to carry drugs, genes, small interfering RNA(si RNA) and growth factors into the inner ear, to repair, restore and induce cellular regeneration. Nanoparticles(NPs) have been developed which are targetable to selected tissue, traceable in vivo, and equipped with controlled drug/gene release. The NPs are coated with a ‘stealth' layer, and decorated with targeting ligands, markers, transfection agents and endosomal escape peptides. As payloads, genes such as the BDNF-gene, Math1-gene and Prestin-gene have been constructed and delivered in vitro. Short-hairpin RNA has been used in vitro to silence the negative regulator of Math1, the inhibitors of differentiation and DNA binding. In order to facilitate the passage of cargo from the middle ear to the inner ear, the oval window transports gadolinium chelate more efficiently than the round window and is the key element in introducing therapeutic agents into the vestibule and cochlea. Depending upon the type of NPs, different migration and cellular internalization pathways are employed, and optimal carriers should be designed depending on the cargo. The use of NPs as drug/gene/si RNA carriers is fascinating and can also be used as an intraoperative adjunct to cochlear implantation to attract the peripheral processes of the cochlear nerve.

鼓室内注射药物治疗梅尼埃病国际专家共识(全译文)

目的:鼓室内(intratympanic,IT)注射药物治疗梅尼埃病(MD)因其疗效显著而备受关注。由于IT注射药物治疗MD的共识和新证据的发布,对IT注射药物治疗MD进行细节上的补充具有重要意义。方法:检索近二十年来有关IT注射药物治疗MD的文献,参考《梅尼埃病治疗国际共识(ICON)》(2018年),《美国梅尼埃病临床实践指南》(2020年)和《梅尼埃病诊断治疗的欧洲立场声明》(2018),并遵循来自欧洲、美国和中国的专家意见。结果:专家一致认为:①鼓室内注射甲泼尼龙(ITM)对眩晕控制的疗效优于鼓室内注射地塞米松(ITD),ITM有恢复MD患者听力的可能性。②由于氨基糖甙类药物的耳毒性,鼓室内注射庆大霉素(ITG)在听力良好MD患者中的应用持谨慎态度。但也有研究表明,小剂量ITG对听力没有显著影响,还需要高水平证据的临床研究进一步证明。③目前普遍接受的ITG治疗终点是在12个月内无眩晕发作或受累耳客观检查提示前庭功能丧失。结论:对IT注射药物治疗MD的药物类型、疗效和治疗终点还需要更多高证据水平的研究进行评价。