A Five-Decade Text Mining Analysis of Cochlear Implant Research: Where We Started and Where We Are Heading.

Background and Objectives: Since its invention in the 1970s, the cochlear implant (CI) has been substantially developed. We aimed to assess the trends in the published literature to characterize CI. Materials and Methods: We queried PubMed for all CI-related entries published during 1970-2022. The following data were extracted: year of publication, publishing journal, title, keywords, and abstract text. Search terms belonged to the patient's age group, etiology for hearing loss, indications for CI, and surgical methodological advancement. Annual trends of publications were plotted. The slopes of publication trends were calculated by fitting regression lines to the yearly number of publications. Results: Overall, 19,428 CIs articles were identified. Pediatric-related CI was the most dominant sub-population among the age groups, with the highest rate and slope during the years (slope 5.2 ± 0.3, p < 0.001), while elderly-related CIs had significantly fewer publications. Entries concerning hearing preservation showed the sharpest rise among the methods, from no entries in 1980 to 46 entries in 2021 (slope 1.7 ± 0.2, p < 0.001). Entries concerning robotic surgery emerged in 2000, with a sharp increase in recent years (slope 0.5 ± 0.1, p < 0.001). Drug-eluting electrodes and CI under local-anesthesia have been reported only in the past five years, with a gradual rise. Conclusions: Publications regarding CI among pediatrics outnumbered all other indications, supporting the rising, pivotal role of CI in the rehabilitation of children with sensorineural hearing loss. Hearing-preservation publications have recently rapidly risen, identified as the primary trend of the current era, followed by a sharp rise of robotic surgery that is evolving and could define the next revolution.

Reduced changes in protein compared to mRNA levels across non-proliferating tissues.

BACKGROUND: The quantitative relations between RNA and protein are fundamental to biology and are still not fully understood. Across taxa, it was demonstrated that the protein-to-mRNA ratio in steady state varies in a direction that lessens the change in protein levels as a result of changes in the transcript abundance. Evidence for this behavior in tissues is sparse. We tested this phenomenon in new data that we produced for the mouse auditory system, and in previously published tissue datasets. A joint analysis of the transcriptome and proteome was performed across four datasets: inner-ear mouse tissues, mouse organ tissues, lymphoblastoid primate samples and human cancer cell lines. RESULTS: We show that the protein levels are more conserved than the mRNA levels in all datasets, and that changes in transcription are associated with translational changes that exert opposite effects on the final protein level, in all tissues except cancer. Finally, we observe that some functions are enriched in the inner ear on the mRNA level but not in protein. CONCLUSIONS: We suggest that partial buffering between transcription and translation ensures that proteins can be made rapidly in response to a stimulus. Accounting for the buffering can improve the prediction of protein levels from mRNA levels.

microRNA-224 regulates Pentraxin 3, a component of the humoral arm of innate immunity, in inner ear inflammation.

microRNAs (miRNAs) are regulators of differentiation and development of inner ear cells. Mutations in miRNAs lead to deafness in humans and mice. Among inner ear pathologies, inflammation may lead to structural and neuronal defects and eventually to hearing loss and vestibular dysfunction. While the genetic factors of these pathways have not been defined, autoimmunity participates in these processes. We report that inflammatory stimuli in the inner ear induce activation of the innate immune system via miR-224 and pentraxin 3 (Ptx3). miR-224 is a transcriptional target of nuclear factor κB, a key mediator of innate immunity. Ptx3 is a regulator of the immune response. It is released in response to inflammation and regulated by nuclear factor κB. We show that miR-224 and Ptx3 are expressed in the inner ear and we demonstrate that miR-224 targets Ptx3. As a model of the innate immune response, we injected lipopolysaccharide into the scala tympani of mouse inner ears. This resulted in changes in the levels of miR-224 and Ptx3, in addition to activation of the complement system, as measured by immune cell infiltration and activated C3. This suggests that while miR-224 regulates Ptx3 under normal conditions, upon inflammation, both are recruited to offer a front line of defense in acting as responders to inflammation in the inner ear. miR-224 diminishes the innate immune response by down-regulating Ptx3 expression, while Ptx3 stimulates the innate immune response. An understanding of the molecular components of the inflammatory pathway may help develop therapeutics for reducing inflammation associated with inner ear injury.

The GPSM2/LGN GoLoco motifs are essential for hearing.

The planar cell polarity (PCP) pathway is responsible for polarizing and orienting cochlear hair cells during development through movement of a primary cilium, the kinocilium. GPSM2/LGN, a mitotic spindle-orienting protein associated with deafness in humans, is a PCP effector involved in kinocilium migration. Here, we link human and mouse truncating mutations in the GPSM2/LGN gene, both leading to hearing loss. The human variant, p.(Trp326*), was identified by targeted genomic enrichment of genes associated with deafness, followed by massively parallel sequencing. Lgn (ΔC) mice, with a targeted deletion truncating the C-terminal GoLoco motifs, are profoundly deaf and show misorientation of the hair bundle and severe malformations in stereocilia shape that deteriorates over time. Full-length protein levels are greatly reduced in mutant mice, with upregulated mRNA levels. The truncated Lgn (ΔC) allele is translated in vitro, suggesting that mutant mice may have partially functioning Lgn. Gαi and aPKC, known to function in the same pathway as Lgn, are dependent on Lgn for proper localization. The polarization of core PCP proteins is not affected in Lgn mutants; however, Lgn and Gαi are misoriented in a PCP mutant, supporting the role of Lgn as a PCP effector. The kinocilium, previously shown to be dependent on Lgn for robust localization, is essential for proper localization of Lgn, as well as Gαi and aPKC, suggesting that cilium function plays a role in positioning of apical proteins. Taken together, our data provide a mechanism for the loss of hearing found in human patients with GPSM2/LGN variants.

Next-generation sequencing of small RNAs from inner ear sensory epithelium identifies microRNAs and defines regulatory pathways.

BACKGROUND: The mammalian inner ear contains sensory organs, the organ of Corti in the cochlea and cristae and maculae in the vestibule, with each comprised of patterned sensory epithelia that are responsible for hearing and balance. The development, cell fate, patterning, and innervation of both the sensory and nonsensory regions of the inner ear are governed by tight regulation involving, among others, transcription factors and microRNAs (miRNAs). In humans, mutations in specific miRNA genes are associated with hearing loss. In mice, experimental reduction or mutations of miRNAs in the inner ear leads to severe developmental and structural abnormalities. A comprehensive identification of miRNAs in the sensory epithelia and their gene targets will enable pathways of auditory and vestibular function to be defined. RESULTS: In this study, we used Next-Generation Sequencing (NGS) to identify the most prominent miRNAs in the inner ear and to define miRNA-target pairs that form pathways crucial for the function of the sensory epithelial cells. NGS of RNA from inner ear sensory epithelial cells led to the identification of 455 miRNAs in both cochlear and vestibular sensory epithelium, with 30 and 44 miRNAs found in only cochlea or vestibule, respectively. miR-6715-3p and miR-6715-5p were defined for the first time in the inner ear. Gene targets were identified for each of these miRNAs, including Arhgap12, a GTPase activating protein, for miR-6715-3p, implicating this miRNA in sensory hair cell bundle development, actin reorganization, cell adhesion and inner ear morphogenesis. CONCLUSIONS: This study provides a comprehensive atlas of miRNAs in the inner ear sensory epithelia. The results provide further support of the essential regulatory role of miRNAs in inner ear sensory epithelia and in regulating pathways that define development and growth of these cells.

Atrophic thyroid follicles and inner ear defects reminiscent of cochlear hypothyroidism in Slc26a4-related deafness.

Thyroid hormone is essential for inner ear development and is required for auditory system maturation. Human mutations in SLC26A4 lead to a syndromic form of deafness with enlargement of the thyroid gland (Pendred syndrome) and non-syndromic deafness (DFNB4). We describe mice with an Slc26a4 mutation, Slc26a4 (loop/loop) , which are profoundly deaf but show a normal sized thyroid gland, mimicking non-syndromic clinical signs. Histological analysis of the thyroid gland revealed defective morphology, with a majority of atrophic microfollicles, while measurable thyroid hormone in blood serum was within the normal range. Characterization of the inner ear showed a spectrum of morphological and molecular defects consistent with inner ear pathology, as seen in hypothyroidism or disrupted thyroid hormone action. The pathological inner ear hallmarks included thicker tectorial membrane with reduced ß-tectorin protein expression, the absence of BK channel expression of inner hair cells, and reduced inner ear bone calcification. Our study demonstrates that deafness in Slc26a4 (loop/loop) mice correlates with thyroid pathology, postulating that sub-clinical thyroid morphological defects may be present in some DFNB4 individuals with a normal sized thyroid gland. We propose that insufficient availability of thyroid hormone during inner ear development plays an important role in the mechanism underlying deafness as a result of SLC26A4 mutations.

Navigating the vestibular maze: text-mining analysis of publication trends over five decades.

Introduction: The field of vestibular science, encompassing the study of the vestibular system and associated disorders, has experienced notable growth and evolving trends over the past five decades. Here, we explore the changing landscape in vestibular science, focusing on epidemiology, peripheral pathologies, diagnosis methods, treatment, and technological advancements. Methods: Publication data was obtained from the US National Center for Biotechnology Information (NCBI) PubMed database. The analysis included epidemiological, etiological, diagnostic, and treatment-focused studies on peripheral vestibular disorders, with a particular emphasis on changes in topics and trends of publications over time. Results: Our dataset of 39,238 publications revealed a rising trend in research across all age groups. Etiologically, benign paroxysmal positional vertigo (BPPV) and Meniere's disease were the most researched conditions, but the prevalence of studies on vestibular migraine showed a marked increase in recent years. Electronystagmography (ENG)/ Videonystagmography (VNG) and Vestibular Evoked Myogenic Potential (VEMP) were the most commonly discussed diagnostic tools, while physiotherapy stood out as the primary treatment modality. Conclusion: Our study presents a unique opportunity and point of view, exploring the evolving landscape of vestibular science publications over the past five decades. The analysis underscored the dynamic nature of the field, highlighting shifts in focus and emerging publication trends in diagnosis and treatment over time.

Virtual Reality Helps Describe the Progression of Thyroid Cartilage Calcification.

OBJECTIVES: Thyroid cartilage (TC) calcifications may impact surgical planning and clinical management. However, few studies to date have implemented virtual reality (VR) to evaluate these calcifications. This study assessed the feasibility of evaluating TC calcifications in various regions and measuring their volumes through VR models generated from computed tomography scans. We also investigated age and gender-related differences in calcification patterns. METHODS: Ninety-two participants were categorized into younger, middle-aged, and older age groups. Calcification patterns (degree in Hounsfield units and volume of calcification in cm3) in different TC regions were identified by VR analysis, which enabled comparisons between age groups and genders. RESULTS: Significant differences in calcification patterns were observed between males and females, particularly in the middle right, middle left, bottom left, and vertex regions. Age-related differences in the vertex region showed increased calcification in the older age group. CONCLUSION: This study points to the contribution of VR in the evaluation of complex anatomical structures. The findings revealed significant gender and age patterns in TC calcification. These insights can inform surgical planning and highlight the potential of using VR to gain a better understanding of TC calcification clinically.

Cytoplasmic mislocalization of POU3F4 due to novel mutations leads to deafness in humans and mice.

POU3F4 is a POU domain transcription factor that is required for hearing. In the ear, POU3F4 is essential for mesenchymal remodeling of the bony labyrinth and is the causative gene for DFNX2 human nonsyndromic deafness. Ear abnormalities underlie this form of deafness, characterized previously in multiple spontaneous, radiation-induced and transgenic mouse mutants. Here, we report three novel mutations in the POU3F4 gene that result in profound hearing loss in both humans and mice. A p.Gln79* mutation was identified in a child from an Israeli family, revealed by massively parallel sequencing (MPS). This strategy demonstrates the strength of MPS for diagnosis with only one affected individual. A second mutation, p.Ile285Argfs*43, was identified by Sanger sequencing. A p.Cys300* mutation was found in an ENU-induced mutant mouse, schwindel (sdl), by positional cloning. The mutation leads to a predicted truncated protein, similar to the human mutations, providing a relevant mouse model. The p.Ile285Argfs*43 and p.Cys300* mutations lead to a shift of Pou3f4 nuclear localization to the cytoplasm, demonstrated in cellular localization studies and in the inner ears of the mutant mice. The discovery of these mutations facilitates a deeper comprehension of the molecular basis of inner ear defects due to mutations in the POU3F4 transcription factor.

The protective effect of aspirin-induced temporary threshold shift in an animal model of cisplatin-related ototoxicity.

PURPOSE: The purpose of this study was to evaluate whether induction of temporary threshold shift (TTS) with aspirin prior to cisplatin exposure can prevent or minimize cisplatin detrimental effects on hearing. METHODS: We randomly divided BALB mice into three groups: (1) cisplatin only, (2) aspirin only, and (3) combined aspirin/cisplatin. Cisplatin was administered as a single intraperitoneal injection of 14 mg/kg. Aspirin was administered for three weeks via intraperitoneal injection of 200 mg/kg sodium salicylate, twice daily. Air conduction thresholds were recorded using Auditory Brainstem Responses (ABR). Cochleae were harvested and cochlear hair cells were counted using a scanning electron microscope (SEM). RESULTS: Aspirin-induced TTS have reached an average of 30.05±16.9 dB after 2 weeks. At 60 days, cisplatin-only treated mice experienced an average threshold shifts of 50.7 dB at 4 kHz, 35.16 dB at 8 kHz, 70 dB at 16 kHz, 53.1 dB at 32 kHz. All threshold shifts were significantly worse than for cisplatin/aspirin treated mice with TTS of 11.85 dB at 4 kHz, 3.58 dB at 8 kHz, 16.58  dB at 16 kHz, 20.41 dB at 32 kHz (p < 0.01). Cochlear cell count with SEM has shown reduction in the number of both inner and outer hair cells in the mid-turn in cisplatin treated mice. CONCLUSION: Aspirin induced TTS can protect from cisplatin-induced ototoxicity. This beneficial effect was demonstrated by auditory thresholds as well as SEM. Larger pre-clinical and clinical studies are still needed to confirm these findings.

The Prevalence of Hearing Impairments in Women with Silicone Breast Implants.

Many women with silicone breast implants (SBIs) report non-specific complaints, including hearing impairments. Hearing impairment appears to be associated with a number of autoimmune conditions. The current study aimed to evaluate the prevalence and severity of hearing impairments among women with SBIs and to explore potential improvements in their hearing capability following implant removal. Symptomatic women with SBIs (n = 160) underwent an initial anamnestic interview, and women who reported hearing impairments were selected for the study. These women completed self-report telephone questionnaires regarding their hearing difficulties. Some of these women underwent subjective and objective hearing tests. Out of 159 (50.3%) symptomatic women with SBIs, 80 reported hearing impairments, including hearing loss (44/80; 55%) and tinnitus (45/80; 56.2%). Five out of seven (71.4%) women who underwent an audiologic evaluation exhibited hearing loss. Of women who underwent silicone implant removal, 27 out of 47 (57.4%) reported the improvement or resolution of their hearing complaints. In conclusion, hearing impairment is a frequent complaint among symptomatic women with SBIs, and tinnitus was found to be the most common complaint. A significant reduction in hearing difficulties was observed following silicone implant removal. Further studies using larger populations are needed to verify the occurrence of hearing impairments in these women.

The Effect of Diathermy Power Settings on Oral Cavity Mucosal Contraction: A Rat Model.

OBJECTIVES/HYPOTHESIS: The effects of different electrocautery power settings on mucosal contraction and margin status in the oral cavity have not been well established. The aim of this study was to examine how different levels of electrocautery energy outputs affect oral mucosal tissue margins. STUDY DESIGN: Animal model. METHODS: A model of 23 adult rats was used (two specimens per rat). After anesthetizing the animals, a 6-mm biopsy punch marked the resection margin on the buccal mucosa (one per cheek). The specimens were excised by means of three energy levels, a cold knife, and monopolar diathermy that was set on either 20 W or 30 W cut modes. The specimens were evaluated for extent of contraction. RESULTS: A total of 45 samples were obtained and measured, including 15 specimens in the cold-knife group, 15 specimens in the 20 W group, and 15 specimens in the 30 W group. The median diameters of the specimens after resection were 4.5 mm for the cold-knife group (interquartile range [IQR] = 4.0-5.0), 3.5 mm for the 20 W group (IQR = 3.5-4.0), and 2.8 mm for the 30 W group (IQR = 2.5-3.0). Specimen contraction was 25.0%, 41.7%, and 53.3%, respectively. The difference in shrinkage between each pair was statistically significant: cold knife versus 20 W, P = .001; cold knife versus 30 W, P < .0001; and 20 W versus 30 W, P < .001. CONCLUSIONS: Diathermy power settings result in a significant difference of mucosal tissue contraction, with higher outputs resulting in a narrower mucosal margin. It is imperative that the surgical team take into consideration the diathermy settings during initial resection planning. Laryngoscope, 131:E1514-E1518, 2021.

Connexin 26 null mice exhibit spiral ganglion degeneration that can be blocked by BDNF gene therapy.

Mutations in the connexin 26 gene (GJB2) are the most common genetic cause of deafness, leading to congenital bilateral non-syndromic sensorineural hearing loss. Here we report the generation of a mouse model for a connexin 26 (Cx26) mutation, in which cre-Sox10 drives excision of the Cx26 gene from non-sensory cells flanking the auditory epithelium. We determined that these conditional knockout mice, designated Gjb2-CKO, have a severe hearing loss. Immunocytochemistry of the auditory epithelium confirmed absence of Cx26 in the non-sensory cells. Histology of the organ of Corti and the spiral ganglion neurons (SGNs) performed at ages 1, 3, or 6 months revealed that in Gjb2-CKO mice, the organ of Corti began to degenerate in the basal cochlear turn at an early stage, and the degeneration rapidly spread to the apex. In addition, the density of SGNs in Rosenthal's canal decreased rapidly along a gradient from the base of the cochlea to the apex, where some SGNs survived until at least 6 months of age. Surviving neurons often clustered together and formed clumps of cells in the canal. We then assessed the influence of brain derived neurotrophic factor (BDNF) gene therapy on the SGNs of Gjb2-CKO mice by inoculating Adenovirus with the BDNF gene insert (Ad.BDNF) into the base of the cochlea via the scala tympani or scala media. We determined that over-expression of BDNF beginning around 1 month of age resulted in a significant rescue of neurons in Rosenthal's canal of the cochlear basal turn but not in the middle or apical portions. This data may be used to design therapies for enhancing the SGN physiological status in all GJB2 patients and especially in a sub-group of GJB2 patients where the hearing loss progresses due to ongoing degeneration of the auditory nerve, thereby improving the outcome of cochlear implant therapy in these ears.

Advances in genetic diagnostics for hereditary hearing loss.

Hereditary hearing loss affects a significant proportion of the hearing impaired, with genetic mutations estimated to be responsible for its etiology in over 50% of this population. The methods for molecular diagnostics are changing as a result of the transition from linkage analysis to next generation sequencing to identify the genes responsible for hearing loss in affected families. In this review, we summarize the attitudes of the hearing impaired towards genetic testing, the latest techniques for identifying mutations, and provide a comprehensive list of the mutations found in the Israeli Jewish hearing-impaired population.

The LINC complex is essential for hearing.

Hereditary hearing loss is the most common sensory deficit. We determined that progressive high-frequency hearing loss in 2 families of Iraqi Jewish ancestry was due to homozygosity for the protein truncating mutation SYNE4 c.228delAT. SYNE4, a gene not previously associated with hearing loss, encodes nesprin-4 (NESP4), an outer nuclear membrane (ONM) protein expressed in the hair cells of the inner ear. The truncated NESP4 encoded by the families' mutation did not localize to the ONM. NESP4 and SUN domain-containing protein 1 (SUN1), which localizes to the inner nuclear membrane (INM), are part of the linker of nucleoskeleton and cytoskeleton (LINC) complex in the nuclear envelope. Mice lacking either Nesp4 or Sun1 were evaluated for hair cell defects and hearing loss. In both Nesp4-/- and Sun1-/- mice, OHCs formed normally, but degenerated as hearing matured, leading to progressive hearing loss. The nuclei of OHCs from mutant mice failed to maintain their basal localization, potentially affecting cell motility and hence the response to sound. These results demonstrate that the LINC complex is essential for viability and normal morphology of OHCs and suggest that the position of the nucleus in sensory epithelial cells is critical for maintenance of normal hearing.