Age-Related Hearing Loss

DSLchild-Algorithm-Based Hearing Aid Fitting Can Improve Speech Comprehension in Mildly Distressed Patients with Chronic Tinnitus and Mild-to-Moderate Hearing Loss

Background: Patients with chronic tinnitus and mild-to-moderate hearing loss (HL) can experience difficulties with speech comprehension (SC). The present study investigated SC benefits of a two-component hearing therapy. Methods: One-hundred-seventy-seven gender-stratified patients underwent binaural DSL_child-algorithm-based hearing aid (HA) fitting and conducted auditory training exercises. SC was measured at four timepoints under three noise interference conditions each (0, 55, and 65 dB): after screening (t₀; without HAs), HA- fitting (t₁), additional auditory training (t₂), and at 70-day follow-up (t₃). Repeated-measure analyses of covariance investigated the effects of HAs (t₀–t₁), auditory training (t₁–t₂), and the stability of the combined effect (t₂–t₃) on SC per noise interference level and HL subgroup. Correlational analyses examined associations between SC, age, and psychological indices. Results: Patients showed mildly elevated tinnitus-related distress, which was negatively associated with SC in patients with mild but not moderate HL. At 0 dB, the intervention lastingly improved SC for patients with mild and moderate HL; at 55 dB, for patients with mild HL only. These effects were mainly driven by HAs. Conclusions: The here-investigated treatment demonstrates some SC-benefit under conditions of no or little noise interference. The auditory training component warrants further investigation regarding non-audiological treatment outcomes.

Idiopathic sudden sensorineural hearing loss: A critique on corticosteroid therapy

Idiopathic sudden sensorineural hearing loss (ISSNHL) is a condition affecting 5-30 per 100,000 individuals with the potential to significantly reduce one's quality of life. The true incidence of this condition is not known because it often goes undiagnosed and/or recovers within a few days. ISSNHL is defined as a ≥30 dB loss of hearing over 3 consecutive audiometric octaves within 3 days with no known cause. The disorder is typically unilateral and most of the cases spontaneously recover to functional hearing within 30 days. High frequency losses, ageing, and vertigo are associated with a poorer prognosis. Multiple causes of ISSNHL have been postulated and the most common are vascular obstruction, viral infection, or labyrinthine membrane breaks. Corticosteroids are the standard treatment option but this practice is not without opposition. Post mortem analyses of temporal bones of ISSNHL cases have been inconclusive. This report analyzed ISSNHL studies administering corticosteroids that met strict inclusion criteria and identified a number of methodologic shortcomings that compromise the interpretation of results. We discuss the issues and conclude that the data do not support present treatment practices. The current status on ISSNHL calls for a multi-institutional, randomized, double-blind trial with validated outcome measures to provide science-based treatment guidance.

The influence of metabolic syndrome on age-related hearing loss from the perspective of mitochondrial dysfunction

With the increase in life expectancy in the global population, aging societies have emerged in many countries, including China. As a common sensory defect in the elderly population, the prevalence of age-related hearing loss and its influence on society are increasing yearly. Metabolic syndrome is currently one of the main health problems in the world. Many studies have demonstrated that metabolic syndrome and its components are correlated with a variety of age-related diseases of the peripheral sensory system, including age-related hearing loss. Both age-related hearing loss and metabolic syndrome are high-prevalence chronic diseases, and many people suffer from both at the same time. In recent years, more and more studies have found that mitochondrial dysfunction occurs in both metabolic syndrome and age-related hearing loss. Therefore, to better understand the impact of metabolic syndrome on age-related hearing loss from the perspective of mitochondrial dysfunction, we reviewed the literature related to the relationship between age-related hearing loss and metabolic syndrome and their components to discern the possible role of mitochondria in both conditions.

Is there an unmet medical need for improved hearing restoration?

Hearing impairment, the most prevalent sensory deficit, affects more than 466 million people worldwide (WHO). We presently lack causative treatment for the most common form, sensorineural hearing impairment; hearing aids and cochlear implants (CI) remain the only means of hearing restoration. We engaged with CI users to learn about their expectations and their willingness to collaborate with health care professionals on establishing novel therapies. We summarize upcoming CI innovations, gene therapies, and regenerative approaches and evaluate the chances for clinical translation of these novel strategies. We conclude that there remains an unmet medical need for improving hearing restoration and that we are likely to witness the clinical translation of gene therapy and major CI innovations within this decade.

A potassium channel agonist protects hearing function and promotes outer hair cell survival in a mouse model for age-related hearing loss

Age-related hearing loss (ARHL) is the most common sensory impairment mainly caused by degeneration of sensory hair cells in the cochlea with no causal medical treatment available. Auditory function and sensory hair cell survival critically depend on the Kv7.4 (KCNQ4) channel, a voltage-gated potassium channel expressed in outer hair cells (OHCs), with its impaired function or reduced activity previously associated with ARHL. Here, we investigated the effect of a potent small-molecule Kv7.4 agonist on ARHL in the senescence-accelerated mouse prone 8 (SAMP8) model. For the first time in vivo, we show that Kv7.4 activation can significantly reduce age-related threshold shifts of auditory brainstem responses as well as OHC loss in the SAMP8 model. Pharmacological activation of Kv7.4 thus holds great potential as a therapeutic approach for ARHL as well as other hearing impairments related to Kv7.4 function.

Neuroprotective role of insulin-like growth factor 1 in auditory and other nervous systems

Insulin-like growth factor 1 (IGF1) exerts an influence on almost every organ system in the body and plays an important role in growth, development, and metabolism. In the nervous system, IGF1 acts by promoting the development and growth of neurons and glial cells, differentiation of Schwann cells and their migration to axons, neurite outgrowth, and neuronal survival. The lack of IGF1 is associated with several pathological conditions, including severe prenatal growth retardation, postnatal growth failure, microcephaly, mental retardation, and bilateral sensorineural hearing loss. In addition to its physiological effects, based on the findings of in vivo and in vitro experiments and clinical trials, IGF1 is considered to play a potential role in the treatment of various types of neuronal damage. In this review, we discuss the potential use of IGF1 as a therapeutic molecule in the nervous system: (1) auditory system, including hair cells, cochlear ribbon synapses, auditory nerve, and central nervous systems, and (2) other peripheral nervous systems, especially the olfactory system and facial nerve. The role of IGF1 in the progression of age-related sensory deficits, especially hearing loss and olfactory dysfunction, is also discussed. Recent studies on IGF1 demonstrated that exogenous IGF1 can be applied in many fields, thus supporting the continued evaluation of IGF1 as a potential therapeutic molecule. Additional scientific investigations should be conducted to further supplement recent findings.

Age-Related Hearing Loss: The Link between Inflammaging, Immunosenescence, and Gut Dysbiosis

This article provides a theoretical overview of the association between age-related hearing loss (ARHL), immune system ageing (immunosenescence), and chronic inflammation. ARHL, or presbyacusis, is the most common sensory disability that significantly reduces the quality of life and has a high economic impact. This disorder is linked to genetic risk factors but is also influenced by a lifelong cumulative effect of environmental stressors, such as noise, otological diseases, or ototoxic drugs. Age-related hearing loss and other age-related disorders share common mechanisms which often converge on low-grade chronic inflammation known as “inflammaging”. Various stimuli can sustain inflammaging, including pathogens, cell debris, nutrients, and gut microbiota. As a result of ageing, the immune system can become defective, leading to the accumulation of unresolved inflammatory processes in the body. Gut microbiota plays a central role in inflammaging because it can release inflammatory mediators and crosstalk with other organ systems. A proinflammatory gut environment associated with ageing could result in a leaky gut and the translocation of bacterial metabolites and inflammatory mediators to distant organs via the systemic circulation. Here, we postulate that inflammaging, as a result of immunosenescence and gut dysbiosis, accelerates age-related cochlear degeneration, contributing to the development of ARHL. Age-dependent gut dysbiosis was included as a hypothetical link that should receive more attention in future studies.

Using Auditory Characteristics to Select Hearing Aid Compression Speeds for Presbycusic Patients

Objectives

This study aimed to select the optimal hearing aid compression speeds (fast-acting and slow-acting) for presbycusic patients by using auditory characteristics including temporal modulation and speech-in-noise performance.

Methods

In total, 24 patients with unilateral or bilateral moderate sensorineural hearing loss who scored higher than 21 on the Montreal Cognitive Assessment (MoCA) test participated in this study. The electrocochleogram (ECochG) results, including summating potentials (SP) and action potentials (AP), were recorded. Subjects' temporal modulation thresholds and speech recognition at 4 individualized signal-to-noise ratios were measured under three conditions, namely, unaided, aided with fast-acting compression (FAC), and aided with slow-acting compression (SAC).

Results

The results of this study showed that modulation discrimination thresholds in the unaided (−8.14 dB) and aided SAC (−8.19 dB) conditions were better than the modulation thresholds in the FAC (−4.67 dB) conditions. The speech recognition threshold (SRT75%) for FAC (5.21 dB) did not differ significantly from SAC (3.39 dB) (p = 0.12). A decision tree analysis showed that the inclusion of the AP, unaided modulation thresholds, and unaided SRT75% may correctly identify the optimal compression speeds (FAC vs. SAC) for individual presbycusic patients with up to 90% accuracy.

Conclusion

Both modes of compression speeds improved a presbycusic patient's speech recognition ability in noise. The SAC hearing aids may better preserve the modulation thresholds than the FAC hearing aids. The measurement of AP, along with the unaided modulation thresholds and unaided SRT75%, may help guide the selection of optimal compression speeds for individual presbycusic patients.

Hearing loss drug discovery and medicinal chemistry: Current status, challenges, and opportunities

Hearing loss is a severe high unmet need condition affecting more than 1.5 billion people globally. There are no licensed medicines for the prevention, treatment or restoration of hearing. Prosthetic devices, such as hearing aids and cochlear implants, do not restore natural hearing and users struggle with speech in the presence of background noise. Hearing loss drug discovery is immature, and small molecule approaches include repurposing existing drugs, combination therapeutics, late-stage discovery optimisation of known chemotypes for identified molecular targets of interest, phenotypic tissue screening and high-throughput cell-based screening. Hearing loss drug discovery requires the integration of specialist therapeutic area biology and otology clinical expertise. Small molecule drug discovery projects in the global clinical portfolio for hearing loss are here collated and reviewed. An overview is provided of human hearing, inner ear anatomy, inner ear delivery, types of hearing loss and hearing measurement. Small molecule experimental drugs in clinical development for hearing loss are reviewed, including their underpinning biology, discovery strategy and activities, medicinal chemistry, calculated physicochemical properties, pharmacokinetics and clinical trial status. SwissADME BOILED-Egg permeability modelling is applied to the molecules reviewed, and these results are considered. Non-small molecule hearing loss assets in clinical development are briefly noted in this review. Future opportunities in hearing loss drug discovery for human genomics and targeted protein degradation are highlighted.

Worsening hearing was associated with higher β-amyloid and tau burden in age-related hearing loss

Age-related hearing loss (ARHL) represents the frequently occurring disability that affects the elderly worldwide. The recent evidence has calculated ARHL to be most potential risk factor to predict dementia. β-amyloid plaques and tau accumulation in brain are hallmarks pathologic feature of Alzheimer's disease (AD), which is a leading cause resulting in dementia. However, the potential mechanistic associations between ARHL and dementia remains unknown. We performed the present cross-sectional cohort study by enrolling 72 patients from research on hearing as well as the pathologic hallmarks of AD in brain. The exposure of hearing was measured by either word recognition score or mean pure-tone of the superior ear. The brain β-amyloid and tau standardized uptake value ratio (SUVR) were measured by positron emission tomography (PET). The covariates included gender, age, cardiovascular disease, education and hearing aid use. To analyze the association between hearing and β-amyloid/tau, linear regression was used and adjusted for potentially confounding covariates. Our data showed that the mean age was 67.1 ± 2.9 years. After adjusted for all the covariates, SUVR of β-amyloid showed an increase of 0.028 [95% confidence interval (CI) 0.004-0.061; P = 0.026], while that of tau exhibited an increase of 0.026 (95% CI 0.003-0.056; P = 0.033) per mean pure-tone increase by 10 dB (worsening). Likewise, per mean word-recognition score increase by 10%, the SUVR of β-amyloid showed an increase of 0.060 (95% CI 0.008-0.113; P = 0.023), while that of tau exhibited an increase of 0.059 (95% CI 0.009-0.111; P = 0.031). Taken together, our data demonstrates that hearing worsening was related to the increased burdens of β-amyloid as well as tau detected by PET, which were the AD pathological markers.

Disrupted Topological Organization of Resting-State Functional Brain Networks in Age-Related Hearing Loss

Purpose

Age-related hearing loss (ARHL), associated with the function of speech perception decreases characterized by bilateral sensorineural hearing loss at high frequencies, has become an increasingly critical public health problem. This study aimed to investigate the topological features of the brain functional network and structural dysfunction of the central nervous system in ARHL using graph theory.

Methods

Forty-six patients with ARHL and forty-five age, sex, and education-matched healthy controls were recruited to undergo a resting-state functional magnetic resonance imaging (fMRI) scan in this study. Graph theory was applied to analyze the topological properties of the functional connectomes by studying the local and global organization of neural networks.

Results

Compared with healthy controls, the patient group showed increased local efficiency (E_loc) and clustering coefficient (C_p) of the small-world network. Besides, the degree centrality (Dc) and nodal efficiency (Ne) values of the left inferior occipital gyrus (IOG) in the patient group showed a decrease in contrast with the healthy control group. In addition, the intra-modular interaction of the occipital lobe module and the inter-modular interaction of the parietal occipital module decreased in the patient group, which was positively correlated with Dc and Ne. The intra-modular interaction of the occipital lobe module decreased in the patient group, which was negatively correlated with the E_loc.

Conclusion

Based on fMRI and graph theory, we indicate the aberrant small-world network topology in ARHL and dysfunctional interaction of the occipital lobe and parietal lobe, emphasizing the importance of dysfunctional left IOG. These results suggest that early diagnosis and treatment of patients with ARHL is necessary, which can avoid the transformation of brain topology and decreased brain function.

Prognostic Gene Expression Signature for Age-Related Hearing Loss

Background

Our study aimed to determine the pathological mechanism of presbycusis at the molecular level, and determine potential biomarkers for the same.

Methods

Differentially expressed genes (DEGs) for presbycusis were obtained by analyzing the microarray data sets (GSE6045 and GSE49543) downloaded from the Gene Expression Omnibus (GEO). Gene ontology (GO), Kyoto Encyclopedia of Genes and Genome (KEGG) pathway, and protein-protein interaction (PPI) network analyses, and Gene Set Enrichment Analysis (GSEA) were performed to analyze the biological functions, molecular pathways, autophagy-related molecular markers, and the immune microenvironment of the DEGs in presbycusis. Then the prognostic roles of the hub genes were analyzed and verified in vivo.

Results

In the old mild hearing loss group (27.7 ± 3.4 months old), 27 down-regulated and 99 up-regulated genes were significantly differentially expressed compared with those in the young control group (3.5 ± 0.4 months old). In the old severe hearing loss group (30.6 ± 1.9 months old), 131 down-regulated and 89 up-regulated genes were significantly differentially expressed compared with those in the young control group. The results of the GO, GSEA, KEGG pathway, and immune infiltration analyses showed that the enrichment terms were mainly focused on immune response in mild presbycusis, and immune response and cell death in severe presbycusis. In the PPI network, autophagy-related genes ATG5, ATG7 showed the highest node scores in mild presbycusis; whereas MTOR, BECN1 showed the highest scores in severe presbycusis. In the GSE49543 data set, four genes (Ywhag, Mapre2, Fgf1, Acss2) were used to construct the prognostic model, and those four genes were significantly up-regulated in the rat model of presbycusis.

Conclusion

Our study is the first to report the difference in autophagy factors and immune microenvironment among different degrees of hearing loss in presbycusis. Furthermore, we provide the prognostic gene expression signature for age-related hearing loss, intending to develop preventative therapies.

Early onset adult deafness in the Rhodesian Ridgeback dog is associated with an in-frame deletion in the EPS8L2 gene

Domestic dogs exhibit diverse types of both congenital and non-congenital hearing losses. Rhodesian Ridgebacks can suffer from a progressive hearing loss in the early stage of their life, a condition known as early onset adult deafness (EOAD), where they lose their hearing ability within 1–2 years after birth. In order to investigate the genetic basis of this hereditary hearing disorder, we performed a genome-wide association study (GWAS) by using a sample of 23 affected and 162 control Rhodesian Ridgebacks. We identified a genomic region on canine chromosome 18 (CFA18) that is strongly associated with EOAD, and our subsequent targeted Sanger sequencing analysis identified a 12-bp inframe deletion in EPS8L2 (CFA18:25,868,739–25,868,751 in the UMICH_Zoey_3.1/canFam5 reference genome build). Additional genotyping confirmed a strong association between the 12-bp deletion and EOAD, where all affected dogs were homozygous for the deletion, while none of the control dogs was a deletion homozygote. A segregation pattern of this deletion in a 2-generation nuclear family indicated an autosomal recessive mode of inheritance. Since EPS8L2 plays a critical role in the maintenance and integrity of the inner ear hair cells in humans and other mammals, the inframe deletion found in this study represents a strong candidate causal mutation for EOAD in Rhodesian Ridgebacks. Genetic and clinical similarities between childhood deafness in humans and EOAD in Rhodesian Ridgebacks emphasizes the potential value of this dog breed in translational research in hereditary hearing disorders.

Transcriptome-Guided Identification of Drugs for Repurposing to Treat Age-Related Hearing Loss

Age-related hearing loss (ARHL) or presbycusis is a prevalent condition associated with social isolation, cognitive impairment, and dementia. Age-related changes in the cochlea, the auditory portion of the inner ear, are the primary cause of ARHL. Unfortunately, there are currently no pharmaceutical approaches to treat ARHL. To examine the biological processes underlying age-related changes in the cochlea and identify candidate drugs for rapid repurposing to treat ARHL, we utilized bulk RNA sequencing to obtain transcriptomes from the functional substructures of the cochlea—the sensorineural structures, including the organ of Corti and spiral ganglion neurons (OC/SGN) and the stria vascularis and spiral ligament (SV/SL)—in young (6-week-old) and old (2-year-old) C57BL/6 mice. Transcriptomic analyses revealed both overlapping and unique patterns of gene expression and gene enrichment between substructures and with ageing. Based on these age-related transcriptional changes, we queried the protein products of genes differentially expressed with ageing in DrugBank and identified 27 FDA/EMA-approved drugs that are suitable to be repurposed to treat ARHL. These drugs target the protein products of genes that are differentially expressed with ageing uniquely in either the OC/SGN or SV/SL and that interrelate diverse biological processes. Further transcriptomic analyses revealed that most genes differentially expressed with ageing in both substructures encode protein products that are promising drug target candidates but are, nevertheless, not yet linked to approved drugs. Thus, with this study, we apply a novel approach to characterize the druggable genetic landscape for ARHL and propose a list of drugs to test in pre-clinical studies as potential treatment options for ARHL.

Extracellular Biomarkers of Inner Ear Disease and Their Potential for Point-of-Care Diagnostics

Rapid diagnostic testing has become a mainstay of patient care, using easily obtained samples such as blood or urine to facilitate sample analysis at the point-of-care. These tests rely on the detection of disease or organ-specific biomarkers that have been well characterized for a particular disorder. Currently, there is no rapid diagnostic test for hearing loss, which is one of the most prevalent sensory disorders in the world. In this review, potential biomarkers for inner ear-related disorders, their detection, and quantification in bodily fluids are described. The authors discuss lesion-specific changes in cell-free deoxyribonucleic acids (DNAs), micro-ribonucleic acids (microRNAs), proteins, and metabolites, in addition to recent biosensor advances that may facilitate rapid and precise detection of these molecules. Ultimately, these biomarkers may be used to provide accurate diagnostics regarding the site of damage in the inner ear, providing practical information for individualized therapy and assessment of treatment efficacy in the future.

Hearing Dysfunction After Treatment With Teprotumumab for Thyroid Eye Disease

PURPOSE

To characterize the frequency, severity, and resolution of hearing dysfunction in patients treated with teprotumumab for thyroid eye disease (TED).

DESIGN

Prospective observational case series.

METHODS

Ophthalmic examination and adverse event assessment, including otologic symptoms, were performed at baseline, after infusions 2, 4, and 8, and at 6-month follow-up in consecutive patients who received at least 4 teprotumumab infusions. Laboratory test results were collected at baseline and during treatment. Audiometry, patulous eustachian tube (PET) testing, and otolaryngology evaluation were obtained for patients with new or worsening otologic symptoms, with a subset obtaining baseline and posttreatment testing.

RESULTS

Twenty-seven patients were analyzed (24 females, 3 males, average 56.3 years old). Twenty-two patients (81.5%) developed new subjective otologic symptoms, after a mean of 3.8 infusions (SD 1.8). At 39.2-week average follow-up after the last infusion, most patients with tinnitus (100%), ear plugging/fullness (90.9%), and autophony (83.3%) experienced symptom resolution, whereas only 45.5% (5 of 11) of patients with subjective hearing loss/decreased word comprehension experienced resolution. Six patients underwent baseline and posttreatment audiometry, 5 of whom developed teprotumumab-related sensorineural hearing loss (SNHL) and 1 patient also developed PET. Three of the 5 patients with teprotumumab-related SNHL had persistent subjective hearing loss at last follow-up. A prior history of hearing loss was discovered as a risk factor for teprotumumab-related SNHL (P = .008).

CONCLUSIONS

Hearing loss is a concerning adverse event of teprotumumab, and its mechanism and reversibility should be further studied. Until risk factors for hearing loss are better understood, we recommend baseline audiometry with PET testing and repeat testing if new otologic symptoms develop. Screening, monitoring, and prevention guidelines are needed.

LncRNA H19 inhibits oxidative stress injury of cochlear hair cells by regulating miR-653-5p/SIRT1 axis

Oxidative stress is one of the important mechanisms of inner ear cell damage, which can lead to age-related hearing loss (ARHL). LncRNA H19 is significantly downregulated in the cochlea of old mouse, however, the role of H19 in the development of ARHL remains unclear. In this study, we aim to investigate the expression and function of H19 in oxidative stress injury of cochlear hair cells induced by HO. RT-qPCR and western blot analysis confirms that HEI-OC1 cells stimulated with HO decreases the expressions of H19 and SIRT1, but increases the expression of miR-653-5p. Overexpression of H19 could increase cell viability, ATP level and mitochondrial membrane potential, but reduce mitochondrial ROS generation and cell apoptosis ratio in HO-stimulated HEI-OC1 cells. MiR-653-5p is a target of H19, which can bind to the 3'-UTR of SIRT1. H19 is found to regulate the expression of SIRT1 through miR-653-5p. Further experiments demonstrates that H19 regulates HEI-OC1 cell viability, ATP level, mitochondrial membrane potential, mitochondrial ROS generation, and cell apoptosis ratio via the miR-653-5p/SIRT1 axis. In conclusion, lncRNA H19 inhibits oxidative stress injury of cochlear hair cells via the miR-653-5p/SIRT1 axis.

Age-Related Hearing Loss: Sensory and Neural Etiology and Their Interdependence

Age-related hearing loss (ARHL) is a common, increasing problem for older adults, affecting about 1 billion people by 2050. We aim to correlate the different reductions of hearing from cochlear hair cells (HCs), spiral ganglion neurons (SGNs), cochlear nuclei (CN), and superior olivary complex (SOC) with the analysis of various reasons for each one on the sensory deficit profiles. Outer HCs show a progressive loss in a basal-to-apical gradient, and inner HCs show a loss in a apex-to-base progression that results in ARHL at high frequencies after 70 years of age. In early neonates, SGNs innervation of cochlear HCs is maintained. Loss of SGNs results in a considerable decrease (~50% or more) of cochlear nuclei in neonates, though the loss is milder in older mice and humans. The dorsal cochlear nuclei (fusiform neurons) project directly to the inferior colliculi while most anterior cochlear nuclei reach the SOC. Reducing the number of neurons in the medial nucleus of the trapezoid body (MNTB) affects the interactions with the lateral superior olive to fine-tune ipsi- and contralateral projections that may remain normal in mice, possibly humans. The inferior colliculi receive direct cochlear fibers and second-order fibers from the superior olivary complex. Loss of the second-order fibers leads to hearing loss in mice and humans. Although ARHL may arise from many complex causes, HC degeneration remains the more significant problem of hearing restoration that would replace the cochlear implant. The review presents recent findings of older humans and mice with hearing loss.

Targeted deletion of the RNA-binding protein Caprin1 leads to progressive hearing loss and impairs recovery from noise exposure in mice

Cell cycle associated protein 1 (Caprin1) is an RNA-binding protein that can regulate the cellular post-transcriptional response to stress. It is a component of both stress granules and neuronal RNA granules and is implicated in neurodegenerative disease, synaptic plasticity and long-term memory formation. Our previous work suggested that Caprin1 also plays a role in the response of the cochlea to stress. Here, targeted inner ear-deletion of Caprin1 in mice leads to an early onset, progressive hearing loss. Auditory brainstem responses from Caprin1-deficient mice show reduced thresholds, with a significant reduction in wave-I amplitudes compared to wildtype. Whilst hair cell structure and numbers were normal, the inner hair cell-spiral ganglion neuron (IHC-SGN) synapse revealed abnormally large post-synaptic GluA2 receptor puncta, a defect consistent with the observed wave-I reduction. Unlike wildtype mice, mild-noise-induced hearing threshold shifts in Caprin1-deficient mice did not recover. Oxidative stress triggered TIA-1/HuR-positive stress granule formation in ex-vivo cochlear explants from Caprin1-deficient mice, showing that stress granules could still be induced. Taken together, these findings suggest that Caprin1 plays a key role in maintenance of auditory function, where it regulates the normal status of the IHC-SGN synapse.

The prevalence and global burden of hearing loss in 204 countries and territories, 1990-2019

We aimed to describe the global prevalence and temporal trends of hearing loss. We collected detailed information of hearing loss from the Global Burden of Disease study between 1990 and 2019. Average annual percentage changes (AAPCs) in hearing loss age-standardized prevalence rate (ASPR), by sex, region, and category, were calculated to quantify the temporal prevalence trends. Globally, the prevalent cases of hearing loss increased from 7514.97×10⁵ in 1990 to 14566.62×10⁵ in 2019, and the ASPR increased from 173.33×10² per 100,000 in 1990 to 177.56×10² per 100,000 in 2019. The years lived with disability (YLDs) increased from 220080.97×10² in 1990 to 402353.05×10² in 2019. The AAPC was 83.27 (95% CI 70.66, 95.88) ×10^-3 in prevalence and -72.87 (95% CI -92.18, -53.56) ×10^-3 in YLDs. Significant correlations of AAPCs with ASPR (r=-0.60, p<0.001), and age-standardized YLD rate (r=-0.43, p=0.0012 for YLD<455, r=0.32, p<0.001 for YLD≥455) were detected. The YLDs of hearing loss owing to occupational noise (HLOON) increased from 39334.39 (95% UI 26881.04, 55999.67) ×10² in 1990 to 70014.49 (98% UI 47605.62, 100593.43) ×10² in 2019, and the increasing AAPC was observed for females and aged between 15 and 49 years old in global and most regions. The age effect was under zero in 7 age groups, the period effect of hearing loss prevalence was increasing and the birth cohort effect was decreasing with the time advance. The number of cases and ASPR of hearing loss in the world is still growing. Efforts to control hearing loss, especially HLOON, are imminent.

Neural Plasticity Induced by Hearing Aid Use

Age-related hearing loss is one of the most prevalent health conditions in older adults. Although hearing aid technology has advanced dramatically, a large percentage of older adults do not use hearing aids. This untreated hearing loss may accelerate declines in cognitive and neural function and dramatically affect the quality of life. Our previous findings have shown that the use of hearing aids improves cortical and cognitive function and offsets subcortical physiological decline. The current study tested the time course of neural adaptation to hearing aids over the course of 6 months and aimed to determine whether early measures of cortical processing predict the capacity for neural plasticity. Seventeen (9 females) older adults (mean age = 75 years) with age-related hearing loss with no history of hearing aid use were fit with bilateral hearing aids and tested in six testing sessions. Neural changes were observed as early as 2 weeks following the initial fitting of hearing aids. Increases in N1 amplitudes were observed as early as 2 weeks following the hearing aid fitting, whereas changes in P2 amplitudes were not observed until 12 weeks of hearing aid use. The findings suggest that increased audibility through hearing aids may facilitate rapid increases in cortical detection, but a longer time period of exposure to amplified sound may be required to integrate features of the signal and form auditory object representations. The results also showed a relationship between neural responses in earlier sessions and the change predicted after 6 months of the use of hearing aids. This study demonstrates rapid cortical adaptation to increased auditory input. Knowledge of the time course of neural adaptation may aid audiologists in counseling their patients, especially those who are struggling to adjust to amplification. A future comparison of a control group with no use of hearing aids that undergoes the same testing sessions as the study's group will validate these findings.

Multidimensional Risk Factors of Age-Related Hearing Loss Among Malaysian Community-Dwelling Older Adults

Purpose

This study evaluates the prevalence of and the multidimensional risk factors associated with age-related hearing loss (ARHL) among community-dwelling older adults in Malaysia.

Patients and Methods

A total of 253 participants aged 60 years and above participated in this cross-sectional study. The participants were subjected to pure tone audiometric assessment. The hearing threshold was calculated for the better ear and classified into pure-tone average (PTA) for the octave frequencies from 0.5 to 4 kHz and high-frequency pure-tone average (HFA) for the octave from 2 to 8kHz. Then, the risk factors associated with PTA hearing loss (HL) and HFAHL were identified by using multivariate logistic regression analysis.

Results

The prevalence of ARHL based on PTA and HFA among the community-dwelling older adults was 75.5% and 83.0%, respectively. Following multifactorial adjustments, being older (OR: 1.239; 95% CI: 1.062–1.445), having higher waist circumference (OR: 1.158; 95% CI: 1.015–1.322), lower intake of niacin (OR: 0.909; 95% CI: 0.831–0.988) and potassium (OR: 0.998; 95% CI: 0.996–1.000), and scoring lower in RAVLT T5 (OR: 0.905; 95% CI: 0.838–0.978) were identified as the risk factors of PTAHL. Meanwhile, being older (OR: 1.117; 95% CI: 1.003–1.244), higher intake of carbohydrate (OR: 1.018; 95% CI: 1.006–1.030), lower intake of potassium (OR: 0.998; 95% CI: 0.997–0.999), and lower scores on the RAVLT T5 (OR: 0.922; 95% CI: 0.874–0.973) were associated with increased risk of having HFAHL.

Conclusion

Increasing age, having higher waist circumference, lower intake of niacin and potassium, higher intake of carbohydrates and having lower RAVLT T5 score were associated with increased risk of ARHL. Modifying these risk factors may be beneficial in preventive and management strategies of ARHL among older persons.

Role of the Stria Vascularis in the Pathogenesis of Sensorineural Hearing Loss: A Narrative Review

Sensorineural hearing loss is a common sensory impairment in humans caused by abnormalities in the inner ear. The stria vascularis is regarded as a major cochlear structure that can independently degenerate and influence the degree of hearing loss. This review summarizes the current literature on the role of the stria vascularis in the pathogenesis of sensorineural hearing loss resulting from different etiologies, focusing on both molecular events and signaling pathways, and further attempts to explore the underlying mechanisms at the cellular and molecular biological levels. In addition, the deficiencies and limitations of this field are discussed. With the rapid progress in scientific technology, new opportunities are arising to fully understand the role of the stria vascularis in the pathogenesis of sensorineural hearing loss, which, in the future, will hopefully lead to the prevention, early diagnosis, and improved treatment of sensorineural hearing loss.

The KEAP1-NRF2 System in Healthy Aging and Longevity

Aging is inevitable, but the inherently and genetically programmed aging process is markedly influenced by environmental factors. All organisms are constantly exposed to various stresses, either exogenous or endogenous, throughout their lives, and the quality and quantity of the stresses generate diverse impacts on the organismal aging process. In the current oxygenic atmosphere on earth, oxidative stress caused by reactive oxygen species is one of the most common and critical environmental factors for life. The Kelch-like ECH-associated protein 1-NFE2-related factor 2 (KEAP1-NRF2) system is a critical defense mechanism of cells and organisms in response to redox perturbations. In the presence of oxidative and electrophilic insults, the thiol moieties of cysteine in KEAP1 are modified, and consequently NRF2 activates its target genes for detoxification and cytoprotection. A number of studies have clarified the contributions of the KEAP1-NRF2 system to the prevention and attenuation of physiological aging and aging-related diseases. Accumulating knowledge to control stress-induced damage may provide a clue for extending healthspan and treating aging-related diseases. In this review, we focus on the relationships between oxidative stress and aging-related alterations in the sensory, glandular, muscular, and central nervous systems and the roles of the KEAP1-NRF2 system in aging processes.

The global hearing therapeutic pipeline: 2021

Hearing loss is a serious condition affecting more than 1.5 billion people globally. Many affected people benefit from the use of devices, such as hearing aids, but these do not restore natural hearing, and many users still struggle to follow speech in the presence of background noise. Consequently, there is rapid growth in work to discover therapeutics to address this need. Our analysis of the therapeutic pipeline for inner ear and central processing disorders identified 23 assets in clinical trials and 56 in preclinical development, of which 25% have entered the pipeline in the past three years. The innovative potential of this pipeline is encouraging, but there are translational hurdles to be overcome. We highlight challenges for the pipeline and comment on opportunities to support and strengthen it.

Web-based transcriptome analysis determines a sixteen-gene signature and associated drugs on hearing loss patients: A bioinformatics approach

Background

Hearing loss is becoming more and more general. It may occur at all age and affect the language learning ability of children and trigger serious social problems.

Methods

The hearing loss differentially expressed genes (HL‐DEGs) were recognized through a comparison with healthy subjects. The Gene Ontology (GO) analysis was executed by DAVID. The reactome analysis of HL‐DEGs was performed by Clue‐GO. Next, we used STRING, an online website, to identify crucial protein‐protein interactions among HL‐DEGs. Cytoscape software was employed to construct a protein‐protein interaction network. MCODE, a plug‐in of the Cytoscape software, was used for module analysis. Finally, we used DGIdb database to ascertain the targeted drugs for MCODE genes.

Results

Four hundred four HL‐DEGs were identified, among which the most up‐regulated 10 genes were AL008707.1, SDR42E1P5, BX005040.1, AL671883.2, MT1XP1, AC016957.1, U2AF1L5, XIST, DAAM2, and ADAMTS2, and the most down‐regulated 10 genes were ALOX15, PRSS33, IL5RA, SMPD3, IGHV1‐2, IGLV3‐9, RHOXF1P1, CACNG6, MYOM2, and RSAD2. Through STRING database and MCODE analysis, we finally got 16 MCODE genes. These genes can be regarded as hearing loss related genes. Through biological analysis, it is found that these genes are enriched in pathways related to apoptosis such as tumor necrosis factor. Among them, MMP8, LTF, ORM2, FOLR3, and TCN1 have corresponding targeted drugs. Foremost, MCODE genes should be investigated for its usefulness as a new biomarker for diagnosis and treatment.

Conclusion

In summary, our study produced a sixteen‐gene signature and associated drugs that could be diagnosis and treatment of hearing loss patients.

Thymoquinone ameliorates age-related hearing loss in C57BL/6J mice by modulating Sirt1 activity and Bak1 expression

Age-related hearing loss (AHL) is the most common sensory disorder of aged population. Currently, one of the most important sources of experimental medicine for AHL is medicinal plants. This study performed the first investigation of the effect of thymoquinone (TQ), a potent antioxidant, on AHL. Here, we used inbred C57BL/6J mice (B6 mice) as a successful experimental model of the early onset of AHL. The behavioral assessment of hearing revealed that the injection of a high dose of TQ (40 mg/kg; TQ40) significantly improved the auditory sensitivity of B6 mice at all tested frequencies (8, 16 and 22 kHz). Histological sections of cochlea from B6 mice injected with a low dose (20 mg/kg; TQ20) and high dose showed relatively less degenerative signs in the modiolus, hair cells and spiral ligaments, the main constituents of the cochlea. In addition, TQ40 completely restored the normal pattern of hair cells in B6 mice, as shown in scanning electron micrographs. Our data indicated that TQ20 and TQ40 reduced levels of Bak1-mediated apoptosis in the cochlea of B6 mice. Interestingly, the level of Sirt1, a positive regulator of autophagy, was significantly increased in B6 mice administered TQ40. In conclusion, TQ relieves the symptoms of AHL by downregulating Bak1 and activating Sirt1 in the cochlea of B6 mice.

Leisure-time physical activity and incidence of objectively assessed hearing loss: The Niigata Wellness Study

Previous cohort study reported that high physical activity was associated with a low risk of self-reported hearing loss in women. However, no studies have examined the association between physical activity and the development of hearing loss as measured using an objective assessment of hearing loss in men and women. Here, we used cohort data to examine the association between leisure-time physical activity and incidence of objectively assessed hearing loss in men and women. Participants included 27 537 Japanese adults aged 20-80 years without hearing loss, who completed a self-administered physical activity questionnaire between April 2001 and March 2002. The participants were followed up for the development of hearing loss as measured by audiometry between April 2002 and March 2008. During follow-up, 3691 participants developed hearing loss. Compared with the none physical activity group, multivariable adjusted hazard ratios (HRs) for developing hearing loss were 0.93 (95% confidence interval (CI), 0.86-1.01) and 0.87 (0.81-0.95) for the medium (<525 MET-min/week) and high (≥525 MET-min/week) physical activity groups, respectively (p for trend = 0.001). The magnitude of risk reduction was slightly greater in vigorous-intensity activity than in moderate-intensity activity (p for interaction = 0.01). Analysis by sound frequency showed that the amount of physical activity was inversely associated with high frequency hearing loss development (p for trend <0.001), but not with low frequency hearing loss development (p for trend = 0.19). Higher level of leisure-time physical activity was associated with lower incidence of hearing loss, particularly for vigorous-intensity activities and high sound frequencies.

Differential regulation of mammalian and avian ATOH1 by E2F1 and its implication for hair cell regeneration in the inner ear

The mammalian inner ear has a limited capacity to regenerate its mechanosensory hair cells. This lack of regenerative capacity underlies the high incidence of age-related hearing loss in humans. In contrast, non-mammalian vertebrates can form new hair cells when damage occurs, a mechanism that depends on re-activation of expression of the pro-hair cell transcription factor Atoh1. Here, we show that members of the E2F transcription factor family, known to play a key role in cell cycle progression, regulate the expression of Atoh1. E2F1 activates chicken Atoh1 by directly interacting with a cis-regulatory region distal to the avian Atoh1 gene. E2F does not activate mouse Atoh1 gene expression, since this regulatory element is absent in mammals. We also show that E2F1 expression changes dynamically in the chicken auditory epithelium during ototoxic damage and hair cell regeneration. Therefore, we propose a model in which the mitotic regeneration of non-mammalian hair cells is due to E2F1-mediated activation of Atoh1 expression, a mechanism which has been lost in mammals.

Wnt Modulation Enhances Otic Differentiation by Facilitating the Enucleation Process but Develops Unnecessary Cardiac Structures

Otic organoids have the potential to resolve current challenges in hearing loss research. The reproduction of the delicate and complex structure of the mammalian cochlea using organoids requires high efficiency and specificity. Recent attempts to strengthen otic organoids have focused on the effects of the Wnt signaling pathway on stem cell differentiation. One important aspect of this is the evaluation of undesirable effects of differentiation after Wnt activation. In the present study, we differentiated mouse embryonic stem cell embryoid bodies (EB) into otic organoids and observed two morphologies with different cell fates. EBs that underwent a core ejection process, or ‘enucleation,’ were similar to previously reported inner ear organoids. Meanwhile, EBs that retained their core demonstrated features characteristic of neural organoids. The application of a Wnt agonist during the maturation phase increased enucleation, as well as otic organoid formation, in turn leading to sensory hair cell-like cell generation. However, with a longer incubation period, Wnt activation also led to EBs with ‘beating’ organoids that exhibited spontaneous movement. This observation emphasizes the necessity of optimizing Wnt enhancement for the differentiation of specific cells, such as those found in the inner ear.

Age-Related Changes in the Cochlea and Vestibule: Shared Patterns and Processes

Both age-related hearing loss (ARHL) and age-related loss in vestibular function (ARVL) are prevalent conditions with deleterious consequences on the health and quality of life. Age-related changes in the inner ear are key contributors to both conditions. The auditory and vestibular systems rely on a shared sensory organ - the inner ear - and, like other sensory organs, the inner ear is susceptible to the effects of aging. Despite involvement of the same sensory structure, ARHL and ARVL are often considered separately. Insight essential for the development of improved diagnostics and treatments for both ARHL and ARVL can be gained by careful examination of their shared and unique pathophysiology in the auditory and vestibular end organs of the inner ear. To this end, this review begins by comparing the prevalence patterns of ARHL and ARVL. Next, the normal and age-related changes in the structure and function of the auditory and vestibular end organs are compared. Then, the contributions of various molecular mechanisms, notably inflammaging, oxidative stress, and genetic factors, are evaluated as possible common culprits that interrelate pathophysiology in the cochlea and vestibular end organs as part of ARHL and ARVL. A careful comparison of these changes reveals that the patterns of pathophysiology show similarities but also differences both between the cochlea and vestibular end organs and among the vestibular end organs. Future progress will depend on the development and application of new research strategies and the integrated investigation of ARHL and ARVL using both clinical and animal models.

Role of Oxidative Stress in the Senescence Pattern of Auditory Cells in Age-Related Hearing Loss

Age-related hearing loss (ARHL) is an increasing and gradual sensorineural hearing dysfunction. Oxidative stress is an essential factor in developing ARHL; additionally, premature senescence of auditory cells induced by oxidative stress can produce hearing loss. Hydrogen peroxide (H₂O₂) represents a method commonly used to generate cellular senescence in vitro. The objective of the present paper is to study H₂O₂-induced senescence patterns in three auditory cell lines (House Ear Institute-Organ of Corti 1, HEI-OC1; organ of Corti, OC-k3, and stria vascularis, SV-k1 cells) to elucidate the intrinsic mechanisms responsible for ARHL. The auditory cells were exposed to H₂O₂ at different concentrations and times. The results obtained show different responses of the hearing cells concerning cell growth, β-galactosidase activity, morphological changes, mitochondrial activation, levels of oxidative stress, and other markers of cell damage (Forkhead box O3a, FoxO3a, and 8-oxoguanine, 8-oxoG). Comparison between the responses of these auditory cells to H₂O₂ is a helpful method to evaluate the molecular mechanisms responsible for these auditory cells' senescence. Furthermore, this in vitro model could help develop anti-senescent therapeutic strategies for the treatment of AHRL.

Olivocochlear Changes Associated With Aging Predominantly Affect the Medial Olivocochlear System

Age-related hearing loss (ARHL) is a public health problem that has been associated with negative health outcomes ranging from increased frailty to an elevated risk of developing dementia. Significant gaps remain in our knowledge of the underlying central neural mechanisms, especially those related to the efferent auditory pathways. Thus, the aim of this study was to quantify and compare age-related alterations in the cholinergic olivocochlear efferent auditory neurons. We assessed, in young-adult and aged CBA mice, the number of cholinergic olivocochlear neurons, auditory brainstem response (ABR) thresholds in silence and in presence of background noise, and the expression of excitatory and inhibitory proteins in the ventral nucleus of the trapezoid body (VNTB) and in the lateral superior olive (LSO). In association with aging, we found a significant decrease in the number of medial olivocochlear (MOC) cholinergic neurons together with changes in the ratio of excitatory and inhibitory proteins in the VNTB. Furthermore, in old mice we identified a correlation between the number of MOC neurons and ABR thresholds in the presence of background noise. In contrast, the alterations observed in the lateral olivocochlear (LOC) system were less significant. The decrease in the number of LOC cells associated with aging was 2.7-fold lower than in MOC and in the absence of changes in the expression of excitatory and inhibitory proteins in the LSO. These differences suggest that aging alters the medial and lateral olivocochlear efferent pathways in a differential manner and that the changes observed may account for some of the symptoms seen in ARHL.

Heat Shock Factor 1 Prevents Age-Related Hearing Loss by Decreasing Endoplasmic Reticulum Stress

Endoplasmic reticulum (ER) stress is a common stress factor during the aging process. Heat shock factor 1 (HSF1) plays a critical role in ER stress; however, its exact function in age-related hearing loss (ARHL) has not been fully elucidated. The purpose of the present study was to identify the role of HSF1 in ARHL. In this study, we demonstrated that the loss of inner and outer hair cells and their supporting cells was predominant in the high-frequency region (basal turn, 32 kHz) in ARHL cochleae. In the aging cochlea, levels of the ER stress marker proteins p-eIF2α and CHOP increased as HSF1 protein levels decreased. The levels of various heat shock proteins (HSPs) also decreased, including HSP70 and HSP40, which were markedly downregulated, and the expression levels of Bax and cleaved caspase-3 apoptosis-related proteins were increased. However, HSF1 overexpression showed significant hearing protection effects in the high-frequency region (basal turn, 32 kHz) by decreasing CHOP and cleaved caspase-3 and increasing the HSP40 and HSP70 proteins. These findings were confirmed by HSF1 functional studies using an auditory cell model. Therefore, we propose that HSF1 can function as a mediator to prevent ARHL by decreasing ER stress-dependent apoptosis in the aging cochlea.

Bidirectional Association Between Depression and Hearing Loss: Evidence From the China Health and Retirement Longitudinal Study

The relationship between depression and age-related hearing loss (ARHL) is not fully understood. This study tested the bidirectional associations between clinically significant depressive symptoms (CSDSs) and ARHL in middle-aged and older adults using data from the China Health and Retirement Longitudinal Study. Among 3,418 participants free of baseline ARHL, baseline CSDS was associated with an increased odds of incident ARHL (odds ratio [OR]: 1.51). Cognitive decline, BMI, and arthritis partially mediated the longitudinal CSDS-ARHL association and explained 24% of the variance in the total effect. Among 4,921 participants without baseline CSDS, baseline ARHL was associated with an increased odds of incident CSDS (OR: 1.37). The bidirectional associations remained significant after adjustments for baseline demographic factors, comorbidities, and other health-related covariates. Depression may contribute to the development of ARHL, and vice versa. Interventions in depression, cognitive decline, and arthritis may delay the onset of ARHL and break the vicious circle between them.

Higher number of teeth is associated with decreased prevalence of hearing impairment in Japan

BACKGROUND/OBJECTIVES

There is limited evidence on the association between tooth loss and hearing impairment (HI). The present cross-sectional study investigated the association between tooth loss and the prevalence of HI in 1004 Japanese adults aged 36 to 84 years.

METHODS

HI was defined as present when pure-tone average was > 25 dB at a frequency of 0.5, 1, 2, and 4 kHz in the better hearing ear. Visual oral examinations were performed. Adjustments were made for age, sex, smoking status, leisure-time physical activity, hypertension, dyslipidemia, diabetes mellitus, history of depression, body mass index, waist circumference, employment, education, and household income.

RESULTS

Of 1004 study subjects, the prevalence of HI was 24.8% (n = 249). Compared with having 28 teeth, having < 22 teeth, but not having 26 to < 28 or 22 to < 26 teeth, was associated with an increased prevalence of HI; the multivariate adjusted ORs (95% CI) of having 26 to < 28, 22 to < 26, and < 22 teeth were 1.41 (0.85-2.38), 1.51 (0.90-2.57), and 1.96 (1.18-3.30), respectively (p for trend = 0.01).

CONCLUSIONS

The results suggest that tooth loss may be associated with an increased prevalence of HI.

Auditory Threshold Variability in the SAMP8 Mouse Model of Age-Related Hearing Loss: Functional Loss and Phenotypic Change Precede Outer Hair Cell Loss

Age-related hearing loss (ARHL) is the most common sensory deficit in aging society, which is accompanied by increased speech discrimination difficulties in noisy environments, social isolation, and cognitive decline. The audiometric degree of ARHL is largely correlated with sensory hair cell loss in addition to age-related factors not captured by histopathological analysis of the human cochlea. Previous studies have identified the senescence-accelerated mouse prone strain 8 (SAMP8) as a model for studying ARHL and age-related modifications of the cochlear redox environment. However, the SAMP8 population exhibits a large variability in auditory function decline over age, whose underlying cause remains unknown. In this study, we analyzed auditory function of SAMP8 mice by measuring auditory brainstem response (ABR) thresholds at the age of 6 weeks (juvenile), 12 weeks (young adult), and 24 weeks (adult). Consistent with previous studies, SAMP8 mice exhibit an early progressive, age-related decline of hearing acuity. However, a spatiotemporal cytohistological analysis showed that the significant increase in threshold variability was not concurrently reflected in outer hair cell (OHC) loss observed in the lower and upper quartiles of the ABR threshold distributions over age. This functional loss was found to precede OHC loss suggesting that age-related phenotypic changes may be contributing factors not represented in cytohistological analysis. The expression of potassium channels KCNQ4 (K_V7.4), which mediates the current I_K,n crucial for the maintenance of OHC membrane potential, and KCNQ1 (K_V7.1), which is an essential component in potassium circulation and secretion into the endolymph generating the endocochlear potential, showed differences between these quartiles and age groups. This suggests that phenotypic changes in OHCs or the stria vascularis due to variable oxidative deficiencies in individual mice may be predictors of the observed threshold variability in SAMP8 mice and their progressive ARHL. In future studies, further phenotypic predictors affected by accumulated metabolic challenges over age need to be investigated as potentially underlying causes of ARHL preceding irreversible OHC loss in the SAMP8 mouse model.

Sex Differences in Otolaryngology: Focus on the Emerging Role of Estrogens in Inflammatory and Pro-Resolving Responses

Otolaryngology (also known as ear, nose, and throat (ENT)) diseases can be significantly affected by the level of sex hormones, which indicates that sex differences affect the manifestation, pathophysiology, and outcomes of these diseases. Recently, increasing evidence has suggested that proinflammatory responses in ENT diseases are linked to the level of sex hormones. The sex hormone receptors are present on a wide variety of immune cells; therefore, it is evident that they play crucial roles in regulating the immune system and hence affect the disease progression of ENT diseases. In this review, we focus on how sex hormones, particularly estrogens, regulate ENT diseases, such as chronic rhinosinusitis, vocal fold polyps, thyroid cancer, Sjögren’s syndrome, and head and neck cancers, from the perspectives of inflammatory responses and specialized proresolving mediator-driven resolution. This paper aims to clarify why considering sex differences in the field of basic and medical research on otolaryngology is a key component to successful therapy for both males and females in the future.

Hearing difficulty is linked to Alzheimer's disease by common genetic vulnerability, not shared genetic architecture

Age-related hearing loss was recently established as the largest modifiable risk factor for Alzheimer's disease (AD), however, the reasons for this link remain unclear. We investigate shared underlying genetic associations using results from recent large genome-wide association studies (GWAS) on adult hearing difficulty and AD. Genetic correlation and Mendelian randomization (MR) analysis do not support a genetic correlation between the disorders, but suggest a direct causal link from AD genetic risk to hearing difficulty, driven by APOE. Systematic MR analyses on the effect of other traits revealed shared effects of glutamine, gamma-glutamylglutamine, and citrate levels on reduced risk of both hearing difficulty and AD. In addition, pathway analysis on GWAS risk variants suggests shared function in neuronal signalling pathways as well as etiology of diabetes and cardiovascular disease. However, after multiple testing corrections, neither analysis led to statistically significant associations. Altogether, our genetic-driven analysis suggests hearing difficulty and AD are linked by a shared vulnerability in molecular pathways rather than by a shared genetic architecture.

Screening Tools and Assessment Methods of Cognitive Decline Associated With Age-Related Hearing Loss: A Review

Strong links between hearing and cognitive function have been confirmed by a growing number of cross-sectional and longitudinal studies. Seniors with age-related hearing loss (ARHL) have a significantly higher cognitive impairment incidence than those with normal hearing. The correlation mechanism between ARHL and cognitive decline is not fully elucidated to date. However, auditory intervention for patients with ARHL may reduce the risk of cognitive decline, as early cognitive screening may improve related treatment strategies. Currently, clinical audiology examinations rarely include cognitive screening tests, partly due to the lack of objective quantitative indicators with high sensitivity and specificity. Questionnaires are currently widely used as a cognitive screening tool, but the subject's performance may be negatively affected by hearing loss. Numerous electroencephalogram (EEG) and magnetic resonance imaging (MRI) studies analyzed brain structure and function changes in patients with ARHL. These objective electrophysiological tools can be employed to reveal the association mechanism between auditory and cognitive functions, which may also find biological markers to be more extensively applied in assessing the progression towards cognitive decline and observing the effects of rehabilitation training for patients with ARHL. In this study, we reviewed clinical manifestations, pathological changes, and causes of ARHL and discussed their cognitive function effects. Specifically, we focused on current cognitive screening tools and assessment methods and analyzed their limitations and potential integration.

A Review on Recent Advancement on Age-Related Hearing Loss: The Applications of Nanotechnology, Drug Pharmacology, and Biotechnology

Aging is considered a contributing factor to many diseases such as cardiovascular disease, Alzheimer’s disease, and hearing loss. Age-related hearing loss, also termed presbycusis, is one of the most common sensory impairments worldwide, affecting one in five people over 50 years of age, and this prevalence is growing annually. Associations have emerged between presbycusis and detrimental health outcomes, including social isolation and mental health. It remains largely untreatable apart from hearing aids, and with no globally established prevention strategies in the clinical setting. Hence, this review aims to explore the pathophysiology of presbycusis and potential therapies, based on a recent advancement in bile acid-based bio-nanotechnologies. A comprehensive online search was carried out using the following keywords: presbycusis, drugs, hearing loss, bile acids, nanotechnology, and more than 150 publications were considered directly relevant. Evidence of the multifaceted oxidative stress and chronic inflammation involvement in cellular damage and apoptosis that is associated with a loss of hair cells, damaged and inflamed stria vascularis, and neuronal signalling loss and apoptosis continues to emerge. New robust and effective therapies require drug delivery deeper into the various layers of the cochlea. Bile acid-based nanotechnology has gained wide interest in its permeation-enhancing ability and potential for numerous applications in treating presbycusis.

Navigating Hereditary Hearing Loss: Pathology of the Inner Ear

Inherited forms of deafness account for a sizable portion of hearing loss among children and adult populations. Many patients with sensorineural deficits have pathological manifestations in the peripheral auditory system, the inner ear. Within the hearing organ, the cochlea, most of the genetic forms of hearing loss involve defects in sensory detection and to some extent, signaling to the brain via the auditory cranial nerve. This review focuses on peripheral forms of hereditary hearing loss and how these impairments can be studied in diverse animal models or patient-derived cells with the ultimate goal of using the knowledge gained to understand the underlying biology and treat hearing loss.

Mitochondrial calcium uniporter is essential for hearing and hair cell preservation in congenic FVB/NJ mice

Mitochondrial Ca²⁺ regulates a wide range of cell processes, including morphogenesis, metabolism, excitotoxicity, and survival. In cochlear hair cells, the activation of mechano-electrical transduction and voltage-gated Ca²⁺ channels result in a large influx of Ca²⁺. The intracellular rise in Ca²⁺ is partly balanced by the mitochondria which rapidly uptakes Ca²⁺ via a highly selective channel comprised of the main pore-forming subunit, the mitochondrial Ca²⁺ uniporter (MCU), and associated regulatory proteins. MCU thus contributes to Ca²⁺ buffering, ensuring cytosolic homeostasis, and is posited to have a critical role in hair cell function and hearing. To test this hypothesis, Ca²⁺ homeostasis in hair cells and cochlear function were investigated in FVB/NJ mice carrying the knockout allele of Mcu (Mcu^+/− or Mcu^−/−). The Mcu knockout allele, which originated in C57BL/6 strain cosegregated along with Cdh23^ahl allele to the FVB/NJ strain, due to the close proximity of these genes. Neither Mcu^+/− nor Mcu^−/− genotypes affected cochlear development, morphology, or Ca²⁺ homeostasis of auditory hair cells in the first two postnatal weeks. However, Mcu^−/− mice displayed high-frequency hearing impairment as early as 3 weeks postnatal, which then progressed to profound hearing loss at all frequencies in about 6 months. In Mcu^+/− mice, significantly elevated ABR thresholds were observed at 6 months and 9 months of age only at 32 kHz frequency. In three-month-old Mcu^−/− mice, up to 18% of the outer hair cells and occasionally some inner hair cells were missing in the mid-cochlear region. In conclusion, mitochondrial Ca²⁺ uniporter is not required for the development of cochlea in mice, but is essential for hearing and hair cell preservation in congenic FVB/NJ mice.

Reprogramming: Emerging Strategies to Rejuvenate Aging Cells and Tissues

Aging is associated with a progressive and functional decline of all tissues and a striking increase in many "age-related diseases". Although aging has long been considered an inevitable process, strategies to delay and potentially even reverse the aging process have recently been developed. Here, we review emerging rejuvenation strategies that are based on reprogramming toward pluripotency. Some of these approaches may eventually lead to medical applications to improve healthspan and longevity.

Gjb3 Gene Mutations in Non-Syndromic Hearing Loss of Bloch, Kurd, and Turkmen Ethnicities in Iran

Background:

Hearing loss (HL) is one of the most common heterogeneous congenital disabilities worldwide. Gap junction protein β-3 (GJB3) gene encodes Connexin31 protein (Cx31). The hereditary type of hearing impairment in this gene are known to cause both autosomal recessive and autosomal dominant form. In addition, GJB3 mutations have been involved in sensorineural deafness, erythrokeratodermia variabilis (EKV), and neuropathy diseases. We aimed to investigate GJB3 mutations in people suffering from HL among three different ethnicities of Iranian population (Baloch, Kurd, and Turkmen).

Methods:

In this descriptive study, 50 GJB2-negative non-syndromic hearing loss (NSHL) Iranian individuals from 3 ethnic groups of Baloch (n=17), Kurd (n =15) and Turkmen (n=18) were enrolled. DNA extractions, PCR, and mutation detection was carried out for the two large deletions of the GJB6, del (GJB6 -D13S1830,) and del (GJB6 -D13S1854) followed by direct DNA sequencing method for the GJB3.

Results:

DNA sequencing of GJB3 was shown a missense heterozygous mutation rs199689484 (NM_024009.3) GJB3: c.340G>A (p.Ala114Thr) in a Baloch patient, and a polymorphism rs35983826 (NM_024009.3) GJB3: c.798C>T (p.Asn266=) in a Turkman patient, in coding region of the GJB3. We did not detect del (GJB6 -D13S1830) and del (GJB6 -D13S1854) among these three ethnicities in Iran.

Conclusion:

Deafness is a heterogeneous disorder. Specific genes and mutations contribute to hearing loss that varies from locus to locus as well as from population to population.

A human induced pluripotent stem cell-based modular platform to challenge sensorineural hearing loss

The sense of hearing depends on a specialized sensory organ in the inner ear, called the cochlea, which contains the auditory hair cells (HCs). Noise trauma, infections, genetic factors, side effects of ototoxic drugs (ie, some antibiotics and chemotherapeutics), or simply aging lead to the loss of HCs and their associated primary neurons. This results in irreversible sensorineural hearing loss (SNHL) as in mammals, including humans; the inner ear lacks the capacity to regenerate HCs and spiral ganglion neurons. SNHL is a major global health problem affecting millions of people worldwide and provides a growing concern in the aging population. To date, treatment options are limited to hearing aids and cochlear implants. A major bottleneck for development of new therapies for SNHL is associated to the lack of human otic cell bioassays. Human induced pluripotent stem cells (hiPSCs) can be induced in two-dimensional and three-dimensional otic cells in vitro models that can generate inner ear progenitors and sensory HCs and could be a promising preclinical platform from which to work toward restoring SNHL. We review the potential applications of hiPSCs in the various biological approaches, including disease modeling, bioengineering, drug testing, and autologous stem cell based-cell therapy, that offer opportunities to understand the pathogenic mechanisms of SNHL and identify novel therapeutic strategies.

Age-related loss of auditory sensitivity in the zebrafish (Danio rerio)

Age-related hearing loss (ARHL), also known as presbycusis, is a widespread and debilitating condition impacting many older adults. Conventionally, researchers utilize mammalian model systems or human cadaveric tissue to study ARHL pathology. Recently, the zebrafish has become an effective and tractable model system for a wide variety of genetic and environmental auditory insults, but little is known about the incidence or extent of ARHL in zebrafish and other non-mammalian models. Here, we evaluated whether zebrafish exhibit age-related loss in auditory sensitivity. The auditory sensitivity of adult wild-type zebrafish (AB/WIK strain) from three adult age subgroups (13-month, 20-month, and 37-month) was characterized using the auditory evoked potential (AEP) recording technique. AEPs were elicited using pure tone stimuli (115-4500 Hz) presented via an underwater loudspeaker and recorded using shielded subdermal metal electrodes. Based on measures of sound pressure and particle acceleration, the mean AEP thresholds of 37-month-old fish [mean sound pressure level (SPL) = 122.2 dB ± 2.2 dB SE re: 1 μPa; mean particle acceleration level (PAL) = -27.5 ± 2.3 dB SE re: 1 ms^-2] were approximately 9 dB higher than that of 20-month-old fish [(mean SPL = 113.1 ± 2.7 dB SE re: 1 μPa; mean PAL = -37.2 ± 2.8 dB re: 1 ms^-2; p = 0.007)] and 6 dB higher than that of 13-month-old fish [(mean SPL = 116.3 ± 2.5 dB SE re: 1 μPa; mean PAL = -34.1 ± 2.6 dB SE re: 1 ms^-2; p = 0.052)]. Lowest AEP thresholds for all three age groups were generally between 800 Hz and 1850 Hz, with no evidence for frequency-specific age-related loss. Our results suggest that zebrafish undergo age-related loss in auditory sensitivity, but the form and magnitude of loss is markedly different than in mammals, including humans. Future work is needed to further describe the incidence and extent of ARHL across vertebrate groups and to determine which, if any, ARHL mechanisms may be conserved across vertebrates to support meaningful comparative/translational studies.