Pathology and mechanisms of cochlear aging

Degradation in Binaural and Spatial Hearing and Auditory Temporal Processing Abilities as a Function of Aging

Objectives

Sensorineural hearing loss is common with advancing age, but even when hearing is normal or near normal in older persons, performance deficits are often seen for suprathreshold listening tasks such as understanding speech in background noise or localizing the direction sounds are coming from. This suggests there is also a more central source of the problem. Objectives of this study were to examine as a function of age (young adult to septuagenarian) performance on: 1) a spatial acuity task examining lateralization ability, and a spatial speech-in-noise (SSIN) recognition task, both measured in a hemi-anechoic sound field using a circular horizontal-plane loudspeaker array, and 2) a suprathreshold auditory temporal processing task and a spectro-temporal processing task, both measured under headphones. Further, we examined any correlations between the measures.

Design

Subjects were 48 adults, aged 21 to 78, with either normal hearing or only a mild sensorineural hearing loss through 4000 Hz. The lateralization task measured minimum audible angle (MAA) for 500 and 4000 Hz narrowband noise (NBN) bursts in diffuse background noise for both an on-axis (subject facing 0°) and off-axis (facing 45°) listening condition at signal-to-noise ratios (SNRs) of -3, -6, -9, and -12 dB. For 42 of the subjects, SSIN testing was also completed for key word recognition in sentences in multi-talker babble noise; specifically, the separation between speech and noise loudspeakers was adaptively varied to determine the difference needed for 40% and 80% correct performance levels. Finally, auditory temporal processing ability was examined using the Temporal Fine Structure test (44 subjects), and the Spectro-Temporal Modulation test (46 subjects).

Results

Mean lateralization performances were poorer (larger MAAs) in older compared to younger subjects, particularly in the more adverse listening conditions (i.e., for 4000 Hz, off-axis, and at poorer SNRs). Performance variability was notably higher for older subjects than for young adults. The 4000 Hz NBN bursts produced larger MAAs than did 500 Hz NBN bursts. The SSIN data also showed declining mean performance with age at both criterion levels, with greater variability again found for older subjects. Spearman rho analyses revealed some low to moderate, but significant correlation coefficients for age versus MAA and for age versus SSIN results. Results from both the TFS and STM showed decreased mean performance with aging, and revealed moderate, significant correlations, with the strongest relationship shown with the TFS test. Finally, of note, extended-high-frequency (EHF) hearing loss (measured between 9000 and 16,000 Hz) was found to increase with aging, but was not seen in the young adult subjects.

Conclusions

Particularly for more adverse listening conditions, age-related deficits were found on both of the spatial hearing tasks and in temporal and spectro-temporal processing abilities. It may be that deficits in temporal processing ability contribute to poorer spatial hearing performance in older subjects due to inaccurate coding of binaural/interaural timing information sent from the periphery to the brainstem. In addition, EHF hearing loss may be a coexisting factor that impacts performance in older subjects.

Biomaterials as a new option for treating sensorineural hearing loss

Sensorineural hearing loss (SNHL) usually involves damage to complex auditory pathways such as inner ear cells and auditory nerves. The highly intricate and nuanced characteristics of these cells render their repair and regeneration extremely challenging, making it difficult to restore hearing to normal levels once it has been compromised. The effectiveness of traditional drugs is so minimal that they provide little help with the treatment. Fortunately, extensive experiments have demonstrated that combining biomaterials with conventional techniques significantly enhances drug effectiveness. This article reviews the research progress of biomaterials in protecting hair cells and the auditory nerve, repairing genes related to hearing, and developing artificial cochlear materials. By organizing the knowledge presented in this article, perhaps new insights can be provided for the clinical management of SNHL.

Re-telling the story of aminoglycoside ototoxicity: tales from sub-Saharan Africa

Background

Aminoglycosides, such as Streptomycin, are cheap, potent antibiotics widely used Sub-Saharan Africa. However, aminoglycosides are the commonest cause of ototoxicity. The limited prospective epidemiological studies on aminoglycoside ototoxicity from Sub-Saharan Africa motivated this study to provide epidemiological information on Streptomycin-induced ototoxicity, identify risk factors and predictors of ototoxicity.

Method

A longitudinal study of 153 adults receiving Streptomycin-based anti-tuberculous drugs was done. All participants underwent extended frequency audiometry and had normal hearing thresholds at baseline. Hearing thresholds were assessed weekly for 2 months, then monthly for the subsequent 6 months. Ototoxicity was determined using the ASHA criteria. Descriptive statistics were used to analyze socio-demographic variables. Ototoxicity incidence rate was calculated, and Kaplan-Meier estimate used to determine cumulative probability of ototoxicity. Chi-square test was done to determine parameters associated with ototoxicity and Cox regression models were used to choose the predictors of ototoxicity.

Results

Age of participants was 41.43 ± 12.66 years, with a male-to-female ratio of 1:0.6. Ototoxicity was found in 34.6% of the participants, giving an incidence of 17.26 per 1,000-person-week. The mean onset time to ototoxicity was 28.0 ± 0.47 weeks. By 28th week, risk of developing ototoxicity for respondents below 40 years of age was 0.29, and for those above 40 years was 0.77. At the end of the follow-up period, the overall probability of developing ototoxicity in the study population was 0.74. A significant difference in onset of ototoxicity was found between the age groups: the longest onset was seen in <40 years, followed by 40-49 years, and shortest onset in ≥50 years. Hazard of ototoxicity was significantly higher in participants aged ≥50 years compared to participants aged ≤40 years (HR = 3.76, 95% CI = 1.84-7.65). The probability of ototoxicity at 40 g, 60 g and 80 g cumulative dose of Streptomycin was 0.08, 0.43 and 2.34, respectively. Age and cumulative dose were significant predictors of ototoxicity.

Conclusion

The mean onset time to Streptomycin-induced ototoxicity was 28 weeks after commencement of therapy. Age and cumulative dose can reliably predict the onset of Streptomycin-induced ototoxicity. Medium to long term monitoring of hearing is advised for patients on aminoglycoside therapy.

Intratympanic Gels for Inner Ear Disorders: A Scoping Review of Clinical Trials

OBJECTIVE

Intratympanic injections are a safe, well tolerated procedure routinely performed by ENT's specialists. Intratympanic injections of gels have the potential to deliver therapeutics into the cochlea through the round window membrane prolonging the release of drugs in the inner ear compartment. Aim of the present review is to summarize clinical trials testing pharmacological treatments for inner ear pathologies through intratympanic gel formulations.

DATA SOURCES

Online databases (Google scholar and PubMed) and registers (Clinicaltrials.gov and Euclinicaltrial) were used to identify clinical trials performed between 1990 and 2022.

REVIEW METHODS

PRISMA criteria have been followed. Clinical trials testing gel formulations administered through local intratympanic injections and targeting inner ear disorders were included. All the reports were identified by the authors working in pairs sequentially selecting only studies respecting the inclusion criteria.

RESULTS

A total of 45 clinical studies have been noticed; the gels for intratympanic injection are in the form of poloxamers or hyaluronic acid combinations; the trials found target different kind of inner ear disorders: acquired-stable SNHL, tinnitus, acute sudden SNHL, Meniere disease, cisplatin induced ototoxicity and hearing preservation in patients undergoing cochlear implant surgery.

CONCLUSION

Few studies listed do not provide the specific kind of gel formulation used but only report the intratympanic delivery vehicle as "gel" or "thermogel". Multiple clinical studies have been targeting several forms of inner ear disorders by injecting different compounds through poloxamer and hyaluronic acid formulations. Larger and more advanced clinical stages are necessary to confirm the efficacy of these chemical compounds.

Surface electrical stimulation of the auditory cortex preserves efferent medial olivocochlear neurons and reduces cochlear traits of age-related hearing loss

The auditory cortex is the source of descending connections providing contextual feedback for auditory signal processing at almost all levels of the lemniscal auditory pathway. Such feedback is essential for cognitive processing. It is likely that corticofugal pathways are degraded with aging, becoming important players in age-related hearing loss and, by extension, in cognitive decline. We are testing the hypothesis that surface, epidural stimulation of the auditory cortex during aging may regulate the activity of corticofugal pathways, resulting in modulation of central and peripheral traits of auditory aging. Increased auditory thresholds during ongoing age-related hearing loss in the rat are attenuated after two weeks of epidural stimulation with direct current applied to the surface of the auditory cortex for two weeks in alternate days (Fernández del Campo et al., 2024). Here we report that the same cortical electrical stimulation protocol induces structural and cytochemical changes in the aging cochlea and auditory brainstem, which may underlie recovery of age-degraded auditory sensitivity. Specifically, we found that in 18 month-old rats after two weeks of cortical electrical stimulation there is, relative to age-matched non-stimulated rats: a) a larger number of choline acetyltransferase immunoreactive neuronal cell body profiles in the ventral nucleus of the trapezoid body, originating the medial olivocochlear system.; b) a reduction of age-related dystrophic changes in the stria vascularis; c) diminished immunoreactivity for the pro-inflammatory cytokine TNFα in the stria vascularis and spiral ligament. d) diminished immunoreactivity for Iba1 and changes in the morphology of Iba1 immunoreactive cells in the lateral wall, suggesting reduced activation of macrophage/microglia; d) Increased immunoreactivity levels for calretinin in spiral ganglion neurons, suggesting excitability modulation by corticofugal stimulation. Altogether, these findings support that non-invasive neuromodulation of the auditory cortex during aging preserves the cochlear efferent system and ameliorates cochlear aging traits, including stria vascularis dystrophy, dysregulated inflammation and altered excitability in primary auditory neurons.

Hearing Loss and Cognitive Decline in the Aging Population: Emerging Perspectives in Audiology

In this perspective article, the author explores the connections between hearing loss, central auditory processing, and cognitive decline, offering insights into the complex dynamics at play. Drawing upon a range of studies, the relationship between age-related central auditory processing disorders and Alzheimer's disease is discussed, with the aim of enhancing our understanding of these interconnected conditions. Highlighting the evolving significance of audiologists in the dual management of cognitive health and hearing impairments, the author focuses on their role in identifying early signs of cognitive impairment and evaluates various cognitive screening tools used in this context. The discussion extends to adaptations of hearing assessments for older adults, especially those diagnosed with dementia, and highlights the significance of objective auditory electrophysiological tests. These tests are presented as vital in assessing the influence of aging and Alzheimer's disease on auditory processing capabilities and to signal cognitive dysfunction. The article underscores the critical role of audiologists in addressing the challenges faced by the aging population. The perspective calls for further research to improve diagnostic and therapeutic strategies in audiology, and emphasizes the need for a multidisciplinary approach in tackling the nexus of hearing loss, auditory processing, and cognitive decline.

Association between oxidative balance score and hearing loss: a cross-sectional study from the NHANES database

Aim

The oxidative balance score (OBS), a composite score of dietary nutrients and lifestyles, reflects an individual's oxidative and antioxidant status. Evidence showed that oxidative stress levels were related to hearing loss. The relationship between OBS and hearing loss remains unclear. This study was to explore the association between OBS and hearing loss in adults.

Methods

In this cross-sectional study, data of participants aged 20-69 years who received hearing tests were extracted from the National Health and Nutrition Examination Survey (NHANES) database (2011-2012, 2015-2016). Hearing loss was defined as hearing threshold >25 dB in either ear. The OBS was composed of 16 dietary nutrients and 4 lifestyles. The covariates were screened using the backward stepwise regression analysis. The association of OBS and hearing loss was assessed with odds ratios (ORs) and 95% confidence intervals (CIs). Subgroups of age, gender, occupational noise exposure, recreational noise exposure, firearm noise exposure, and veteran status were further evaluated the associations. The importance ranking of OBS components was analyzed by the weighted random forest model.

Results

Of the total 3,557 adults, 338 (9.5%) suffered from hearing loss. High OBS levels were associated with lower odds of hearing loss (OR = 0.58, 95%CI: 0.41-0.82), after adjusting age, gender, race, hypertension, tinnitus, recreational noise exposure, and occupational noise exposure. Similar results were discovered in individuals aged50-59 years old (OR = 0.47, 95%CI: 0.24-0.93), aged 60-69 years old (OR = 0.31, 95%CI: 0.16-0.61), with female (OR = 0.44, 95%CI: 0.20-0.96), without occupational noise exposure (OR = 0.31, 95%CI: 0.16-0.62), recreational noise exposure (OR = 0.48, 95%CI: 0.30-0.76), firearm noise exposure (OR = 0.38, 95%CI: 0.19-0.77), and veteran status (OR = 0.57, 95%CI: 0.39-0.82). In OBS components, vitamin B12, total fat and physical activity were important for hearing loss.

Conclusion

Elevated OBS may be associated with hearing health in adults. Appropriate vitamin B12 supplementation, reduction of total fat intake, and increased physical activity may be beneficial to the prevention of hearing loss.

Deafness-associated tRNAPhe mutation impaired mitochondrial and cellular integrity

Defects in mitochondrial RNA metabolism have been linked to sensorineural deafness that often occurs as a consequence of damaged or deficient inner ear hair cells. In this report, we investigated the molecular mechanism underlying a deafness-associated tRNAPhe 593T > C mutation that changed a highly conserved uracil to cytosine at position 17 of the DHU-loop. The m.593T > C mutation altered tRNAPhe structure and function, including increased melting temperature, resistance to S1 nuclease-mediated digestion, and conformational changes. The aberrant tRNA metabolism impaired mitochondrial translation, which was especially pronounced by decreases in levels of ND1, ND5, CYTB, CO1, and CO3 harboring higher numbers of phenylalanine. These alterations resulted in aberrant assembly, instability, and reduced activities of respiratory chain enzyme complexes I, III, IV, and intact supercomplexes overall. Furthermore, we found that the m.593T > C mutation caused markedly diminished membrane potential, and increased the production of reactive oxygen species in the mutant cell lines carrying the m.593T > C mutation. These mitochondrial dysfunctions led to the mitochondrial dynamic imbalance via increasing fission with abnormal mitochondrial morphology. Excessive fission impaired the process of autophagy including the initiation phase, formation, and maturation of the autophagosome. In particular, the m.593T > C mutation upregulated the PARKIN-dependent mitophagy pathway. These alterations promoted an intrinsic apoptotic process for the removal of damaged cells. Our findings provide critical insights into the pathophysiology of maternally inherited deafness arising from tRNA mutation-induced defects in mitochondrial and cellular integrity.

L-Ergothioneine slows the progression of age-related hearing loss in CBA/CaJ mice

The naturally occurring amino acid, l-ergothioneine (EGT), has immense potential as a therapeutic, having shown promise in the treatment of other disease models, including neurological disorders. EGT is naturally uptaken into cells via its specific receptor, OCTN1, to be utilized by cells as an antioxidant and anti-inflammatory. In our current study, EGT was administered over a period of 6 months to 25-26-month-old CBA/CaJ mice as a possible treatment for age-related hearing loss (ARHL), since presbycusis has been linked to higher levels of cochlear oxidative stress, apoptosis, and chronic inflammation. Results from the current study indicate that EGT can prevent aging declines of some key features of ARHL. However, we found a distinct sex difference for the response to the treatments, for hearing - Auditory Brainstem Responses (ABRs) and Distortion Product Otoacoustic Emissions (DPOAEs). Males exhibited lower threshold declines in both low dose (LD) and high dose (HD) test groups throughout the testing period and did not display some of the characteristic aging declines in hearing seen in Control animals. In contrast, female mice did not show any therapeutic effects with either treatment dose. Further confirming this sex difference, EGT levels in whole blood sampling throughout the testing period showed greater uptake of EGT in males compared to females. Additionally, RT-PCR results from three tissue types of the inner ear confirmed EGT activity in the cochlea in both males and females. Males and females exhibited significant differences in biomarkers related to apoptosis (Cas-3), inflammation (TNF-a), oxidative stress (SOD2), and mitochondrial health (PGC1a).These changes were more prominent in males as compared to females, especially in stria vascularis tissue. Taken together, these findings suggest that EGT has the potential to be a naturally derived therapeutic for slowing down the progression of ARHL, and possibly other neurodegenerative diseases. EGT, while effective in the treatment of some features of presbycusis in aging males, could also be modified into a general prophylaxis for other age-related disorders where treatment protocols would include eating a larger proportion of EGT-rich foods or supplements. Lastly, the sex difference discovered here, needs further investigation to see if therapeutic conditions can be developed where aging females show better responsiveness to EGT.

The emerging roles and therapeutic implications of immunosenescence-mediated inflammaging in age-related hearing loss

Age-related hearing loss (ARHL) represents one of the most prevalent chronic sensory deficits experienced by the elderly, significantly diminishing their quality of life and correlating with various medical and psychological morbidities. This condition arises from the cumulative effects of aging on the auditory system, implicating intricate interactions between genetic predispositions and environmental factors. Aging entails a progressive decline in immune system functionality, termed immunosenescence, leading to a chronic low-grade inflammation known as inflammaging. This phenomenon potentially serves as a common mechanism underlying ARHL and other age-related pathologies. Recent research suggests that rejuvenating immunosenescence could mitigate inflammaging and ameliorate age-related functional declines, offering promising insights into anti-aging therapies. Consequently, this review endeavors to elucidate the role of immunosenescence-mediated inflammaging in ARHL progression and discuss its therapeutic implications.

Unveiling the Role of Oxidative Stress in Cochlear Hair Cell Death: Prospective Phytochemical Therapeutics against Sensorineural Hearing Loss

Hearing loss represents a multifaceted and pervasive challenge that deeply impacts various aspects of an individual's life, spanning psychological, emotional, social, and economic realms. Understanding the molecular underpinnings that orchestrate hearing loss remains paramount in the quest for effective therapeutic strategies. This review aims to expound upon the physiological, biochemical, and molecular aspects of hearing loss, with a specific focus on its correlation with diabetes. Within this context, phytochemicals have surfaced as prospective contenders in the pursuit of potential adjuvant therapies. These compounds exhibit noteworthy antioxidant and anti-inflammatory properties, which hold the potential to counteract the detrimental effects induced by oxidative stress and inflammation-prominent contributors to hearing impairment. Furthermore, this review offers an up-to-date exploration of the diverse molecular pathways modulated by these compounds. However, the dynamic landscape of their efficacy warrants recognition as an ongoing investigative topic, inherently contingent upon specific experimental models. Ultimately, to ascertain the genuine potential of phytochemicals as agents in hearing loss treatment, a comprehensive grasp of the molecular mechanisms at play, coupled with rigorous clinical investigations, stands as an imperative quest.

Excessive processing and acetylation of OPA1 aggravate age-related hearing loss via the dysregulation of mitochondrial dynamics

The pathogenesis of age-related hearing loss (ARHL) remains unclear. OPA1 is the sole fusion protein currently known to be situated in the inner mitochondrial membrane, which is pivotal for maintaining normal mitochondrial function. While it has already been demonstrated that mutations in OPA1 may lead to hereditary deafness, its involvement in the occurrence and development of ARHL has not been previously explored. In our study, we constructed D-gal-induced senescent HEI-OC1 cells and the cochlea of C57BL/6J mice with a mutated SUMOylation site of SIRT3 using CRISPR/Cas9 technology. We found enhanced L-OPA1 processing mediated by activated OMA1, and increased OPA1 acetylation resulting from reductions in SIRT3 levels in senescent HEI-OC1 cells. Consequently, the fusion function of OPA1 was inhibited, leading to mitochondrial fission and pyroptosis in hair cells, ultimately exacerbating the aging process of hair cells. Our results suggest that the dysregulation of mitochondrial dynamics in cochlear hair cells in aged mice can be ameliorated by activating the SIRT3/OPA1 signaling. This has the potential to alleviate the senescence of cochlear hair cells and reduce hearing loss in mice. Our study highlights the significant roles played by the quantities of long and short chains and the acetylation activity of OPA1 in the occurrence and development of ARHL. This finding offers new perspectives and potential targets for the prevention and treatment of ARHL.

Potential role of modulating autophagy levels in sensorineural hearing loss

In recent years, extensive research has been conducted on the pathogenesis of sensorineural hearing loss (SNHL). Apoptosis and necrosis have been identified to play important roles in hearing loss, but they cannot account for all hearing loss. Autophagy, a cellular process responsible for cell self-degradation and reutilization, has emerged as a significant factor contributing to hearing loss, particularly in cases of autophagy deficiency. Autophagy plays a crucial role in maintaining cell health by exerting cytoprotective and metabolically homeostatic effects in organisms. Consequently, modulating autophagy levels can profoundly impact the survival, death, and regeneration of cells in the inner ear, including hair cells (HCs) and spiral ganglion neurons (SGNs). Abnormal mitochondrial autophagy has been demonstrated in animal models of SNHL. These findings indicate the profound significance of comprehending autophagy while suggesting that our perspective on this cellular process holds promise for advancing the treatment of SNHL. Thus, this review aims to clarify the pathogenic mechanisms of SNHL and the role of autophagy in the developmental processes of various cochlear structures, including the greater epithelial ridge (GER), SGNs, and the ribbon synapse. The pathogenic mechanisms of age-related hearing loss (ARHL), also known as presbycusis, and the latest research on autophagy are also discussed. Furthermore, we underscore recent findings on the modulation of autophagy in SNHL induced by ototoxic drugs. Additionally, we suggest further research that might illuminate the complete potential of autophagy in addressing SNHL, ultimately leading to the formulation of pioneering therapeutic strategies and approaches for the treatment of deafness.

Age-related changes in the zebrafish and killifish inner ear and lateral line

Age-related hearing loss (ARHL) is a debilitating disorder for millions worldwide. While there are multiple underlying causes of ARHL, one common factor is loss of sensory hair cells. In mammals, new hair cells are not produced postnatally and do not regenerate after damage, leading to permanent hearing impairment. By contrast, fish produce hair cells throughout life and robustly regenerate these cells after toxic insult. Despite these regenerative abilities, zebrafish show features of ARHL. Here, we show that aged zebrafish of both sexes exhibited significant hair cell loss and decreased cell proliferation in all inner ear epithelia (saccule, lagena, utricle). Ears from aged zebrafish had increased expression of pro-inflammatory genes and significantly more macrophages than ears from young adult animals. Aged zebrafish also had fewer lateral line hair cells and less cell proliferation than young animals, although lateral line hair cells still robustly regenerated following damage. Unlike zebrafish, African turquoise killifish (an emerging aging model) only showed hair cell loss in the saccule of aged males, but both sexes exhibit age-related changes in the lateral line. Our work demonstrates that zebrafish exhibit key features of auditory aging, including hair cell loss and increased inflammation. Further, our finding that aged zebrafish have fewer lateral line hair cells yet retain regenerative capacity, suggests a decoupling of homeostatic hair cell addition from regeneration following acute trauma. Finally, zebrafish and killifish show species-specific strategies for lateral line homeostasis that may inform further comparative research on aging in mechanosensory systems.

Multisession anodal epidural direct current stimulation of the auditory cortex delays the progression of presbycusis in the Wistar rat

Presbycusis or age-related hearing loss (ARHL) is one of the most prevalent chronic health problems facing aging populations. Along the auditory pathway, the stations involved in transmission and processing, function as a system of interconnected feedback loops. Regulating hierarchically auditory processing, auditory cortex (AC) neuromodulation can, accordingly, activate both peripheral and central plasticity after hearing loss. However, previous ARHL-prevention interventions have mainly focused on preserving the structural and functional integrity of the inner ear, overlooking the central auditory system. In this study, using an animal model of spontaneous ARHL, we aim at assessing the effects of multisession epidural direct current stimulation of the AC through stereotaxic implantation of a 1-mm silver ball anode in Wistar rats. Consisting of 7 sessions (0.1 mA/10 min), on alternate days, in awake animals, our stimulation protocol was applied at the onset of hearing loss (threshold shift detection at 16 months). Click- and pure-tone auditory brainstem responses (ABRs) were analyzed in two animal groups, namely electrically stimulated (ES) and non-stimulated (NES) sham controls, comparing recordings at 18 months of age. At 18 months, NES animals showed significantly increased threshold shifts, decreased wave amplitudes, and increased wave latencies after click and tonal ABRs, reflecting a significant, spontaneous ARHL evolution. Conversely, in ES animals, no significant differences were detected in any of these parameters when comparing 16 and 18 months ABRs, indicating a delay in ARHL progression. Electrode placement in the auditory cortex was accurate, and the stimulation did not cause significant damage, as shown by the limited presence of superficial reactive microglial cells after IBA1 immunostaining. In conclusion, multisession DC stimulation of the AC has a protective effect on auditory function, delaying the progression of presbycusis.

Hearing loss and history of otolaryngological conditions in adults with microdeletion 22q11.2

Previous studies have shown that the 22q11.2 microdeletion, associated with 22q11.2 deletion syndrome (22q11.2DS), conveys an increased risk of chronic otitis media, and hearing loss at young age. This study reports on hearing loss and history of otolaryngological conditions in adults with 22q11.2DS. We conducted a retrospective study of 60 adults with 22q11.2DS (41.7% male) at median age 25 (range 16-74) years who had visited an otolaryngologist and audiologist for routine assessment at a 22q11.2 expert center. Demographic, genetic, audiometric, and otolaryngological data were systematically extracted from the medical files. Regression analysis was used to evaluate the effect of age, sex, full-scale intelligence quotient, and history of chronic otitis media on the severity of hearing loss. Hearing loss, mostly high-frequency sensorineural, was found in 78.3% of adults. Higher age and history of chronic otitis media were associated with more severe hearing loss. Otolaryngological conditions with possible treatment implications included chronic otitis media (56.7%), globus pharyngeus (18.3%), balance problems (16.7%), and obstructive sleep apnea (8.3%). The results suggest that  in 22q11.2DS, high-frequency hearing loss appears to be common from a young adult age, and often unrecognized. Therefore, we recommend periodic audiometric screening in all adults, including high-frequency ranges.

Investigation of Age and Gender Effects on the Middle Ear With Wideband Tympanometry in Adults

OBJECTIVES

Several studies have reported the effects of age and gender on the middle ear of adults using wideband acoustic immittance (WAI) that measures middle ear function over a range of frequencies rather than the traditional measures with a single probe tone. Although these results are often based on WAI measurements under ambient pressure, using WAI under varying ear-canal pressures (wideband tympanometry [WBT]) may be able to provide more information about age and gender effects on the middle ear. The aim of this study is to examine the effects of age and gender on the middle ear with WBT in three different age groups consisting of young, middle-aged, and older adults.

DESIGN

A total of 95 adults with normal middle ear function were assessed, including 32 young adults (16 men, 16 women, aged 20 to 39 years), 31 middle-aged adults (15 men, 16 women, aged 41 to 60 years), and 32 older adults (16 men, 16 women, aged 65 to 82 years). WBT measurements were performed from 226 to 8000 Hz using Interacoustics Titan. Energy absorbance data at tympanometric peak pressure (EA TPP ) and ambient pressure (EA AP ) at 1/3 octave frequencies, and resonance frequency (RF) data were analyzed according to age and gender variables.

RESULTS

Analysis results showed that the mean EA TPP was significantly higher from 500 to 794 Hz and at 5040 and 6350 Hz, and significantly lower from 1587 to 3175 Hz in older adults compared with young adults. The mean EA AP was significantly lower from 1587 to 3175 Hz, and significantly higher at 5040 and 6350 Hz in older adults compared with young adults. There was no significant difference in the mean EA TPP and mean EA AP at any frequency between young and middle-aged adults, and middle-aged and older adults. RF was significantly lower in older adults compared with young adults. In all age groups, men had higher mean EA TPP and mean EA AP at lower frequencies and lower mean EA TPP and mean EA AP at higher frequencies than women. Men had slightly lower RF than women in young and older adults, while men had significantly lower RF than women in middle-aged adults.

CONCLUSIONS

This study demonstrated that there are possible age and gender effects on the middle ear that may affect the mechanical transmission of sound. It may be useful to consider this finding in clinical evaluation in adults of different ages and genders, and to establish age- and gender-specific WBT norms in the adult population.

Persistently short or long sleep duration increases the risk of sensory impairment in Chinese older adults

Background

Cross-sectional evidence suggests that persistently short or long sleep duration is associated with sensory impairment. Thus, this study was conducted to investigate the associations between sleep duration and altered sleep duration with sensory impairment in Chinese older adults.

Methods

Longitudinal data (2008-2014) obtained through the Chinese Longitudinal Healthy Longevity Survey (CLHLS) were analyzed. Sleep duration was classified as normal (7-8 h), short (<7 h), or long (≥9 h). Sensory impairment was assessed using individuals' self-reported data on visual and hearing functions. Cox regression was performed to evaluate the effects of sleep duration and altered sleep duration on sensory impairment, including visual impairment (VI) and hearing impairment (HI).

Results

This study included 3,578 older adults (mean age: 78.12 ± 9.59 years). Among them, 2,690 (75.2%) were aged 65-84 years and 1798 (50.3%) were women. The risks of VI (hazard ratio [HR]: 1.14; 95% confidence interval [CI]: 1.02-1.29), HI (HR: 1.14; 95% CI: 1.00-1.30), and dual sensory impairment (both VI and HI; HR: 1.26; 95% CI: 1.03-1.55) were high in older adults with long sleep duration. In addition, the risks of VI, HI, and dual sensory impairment were high in individuals whose sleep duration changed from normal to short or long (HR: 1.20 [95% CI: 1.02-1.42], 1.26 [95% CI: 1.03-1.53], and 1.54 [95% CI: 1.11-2.12], respectively) and those with persistently short or long sleep duration (HR: 1.25 [95% CI: 1.07-1.46], 1.34 [95% CI: 1.11-1.61], and 1.67 [95% CI: 1.22-2.27], respectively).

Conclusion

A prospective association was identified between altered sleep duration and sensory impairment in Chinese older adults. Our findings highlight the importance of optimal sleep duration and healthy sleep habits in preventing sensory impairment in older adults.

Health position paper and redox perspectives - Disease burden by transportation noise

Transportation noise is a ubiquitous urban exposure. In 2018, the World Health Organization concluded that chronic exposure to road traffic noise is a risk factor for ischemic heart disease. In contrast, they concluded that the quality of evidence for a link to other diseases was very low to moderate. Since then, several studies on the impact of noise on various diseases have been published. Also, studies investigating the mechanistic pathways underlying noise-induced health effects are emerging. We review the current evidence regarding effects of noise on health and the related disease-mechanisms. Several high-quality cohort studies consistently found road traffic noise to be associated with a higher risk of ischemic heart disease, heart failure, diabetes, and all-cause mortality. Furthermore, recent studies have indicated that road traffic and railway noise may increase the risk of diseases not commonly investigated in an environmental noise context, including breast cancer, dementia, and tinnitus. The harmful effects of noise are related to activation of a physiological stress response and nighttime sleep disturbance. Oxidative stress and inflammation downstream of stress hormone signaling and dysregulated circadian rhythms are identified as major disease-relevant pathomechanistic drivers. We discuss the role of reactive oxygen species and present results from antioxidant interventions. Lastly, we provide an overview of oxidative stress markers and adverse redox processes reported for noise-exposed animals and humans. This position paper summarizes all available epidemiological, clinical, and preclinical evidence of transportation noise as an important environmental risk factor for public health and discusses its implications on the population level.

Identification and experimental validation of ferroptosis-related gene lactotransferrin in age-related hearing loss

Objective

To reveal the relationship between ARHL and ferroptosis and screen ferroptosis-related genes (FRGs) in ARHL.

Methods

Bioinformatics were used to analyze the hub genes and molecular mechanism of ferroptosis in the aging cochleae. Senescence β-galactosidase staining, iron content detection, and micro malondialdehyde (MDA) assay kits were used to measure β-galactosidase activity, and expression of Fe2+ and MDA, respectively. Fluorescence microscope was used for immunofluorescence assay of hub genes. Western blot was used to verify the expression of hub genes in HEI-OC1 cells, cochlear explants, and cochleae of C57BL/6J mice. Data were expressed as mean ± SD of at least three independent experiments.

Results

The analysis of bioinformatics confirmed that lactotransferrin (LTF) is the hub gene and CEBPA-miR-130b-LTF network is the molecular mechanism for cochlear ferroptosis. Compared with the control group, the experiments proved that the indicators of ferroptosis, including Fe2+, MDA, and LTF were differentially expressed in aging HEI-OC1 cells, aging cochlear explants, and aging cochleae.

Conclusion

These results demonstrate that ferroptosis plays an important role in ARHL, and LTF is a potential therapeutic target for ARHL via regulating cochlear ferroptosis.

Mitophagy Decreases in the Peripheral Vestibular System of Aged C57BL/6J Mice

BACKGROUND/AIM

Mitophagy is a cardinal process for maintaining healthy and functional mitochondria. A decline in mitophagy has been associated with age-related pathologies. We aimed to investigate mitophagy changes in age-related balance problems using an animal model.

MATERIALS AND METHODS

C57BL/6J mice were divided into young (1 month old) and aged (12 months old) groups. Balance performance, mitochondrial DNA integrity, ATP content, mitophagic process, and mitophagy-related genes and proteins were investigated in both groups.

RESULTS

Balance and motor performance were reduced in the aged group. Mitochondrial DNA integrity and ATP content, and mRNA levels of PINK1, Parkin, BNIP3, AMBRA1, MUL1, NIX, Bcl2-L-13, Atg3, Atg5, Atg12, and Atg13 in the vestibule were significantly lower in aged mice compared with those in young mice. The protein levels of PINK1, Parkin, BNIP3, LC3B, and OXPHOS subunits were significantly decreased in the aged vestibule. Mitophagosome and mitophagolysosome counts and the immunohistochemical expression of Parkin and BNIP3 were also decreased in the saccule, utricle, and crista ampullaris in the aged group.

CONCLUSION

A general decrease in mitophagy with aging might be attributed to a decrease in cellular function in the aged vestibule during the development of age-related balance problems.

Microbubble-assisted ultrasound for inner ear drug delivery

Treating pathologies of the inner ear is a major challenge. To date, a wide range of procedures exists for administering therapeutic agents to the inner ear, with varying degrees of success. The key is to deliver therapeutics in a way that is minimally invasive, effective, long-lasting, and without adverse effects on vestibular and cochlear function. Microbubble-assisted ultrasound ("sonoporation") is a promising new modality that can be adapted to the inner ear. Combining ultrasound technology with microbubbles in the middle ear can increase the permeability of the round window, enabling therapeutic agents to be delivered safely and effectively to the inner ear in a targeted manner. As such, sonoporation is a promising new approach to treat hearing loss and vertigo. This review summarizes all studies on the delivery of therapeutic molecules to the inner ear using sonoporation.

Auditory brainstem responses in the nine-banded armadillo (Dasypus novemcinctus)

The auditory brainstem response (ABR) to tone burst stimuli of thirteen frequencies ranging from 0.5 to 48 kHz was recorded in the nine-banded armadillo (Dasypus novemcinctus), the only extant member of the placental mammal superorder Xenarthra in North America. The armadillo ABR consisted of five main peaks that were visible within the first 10 ms when stimuli were presented at high intensities. The latency of peak I of the armadillo ABR increased as stimulus intensity decreased by an average of 20 μs/dB. Estimated frequency-specific thresholds identified by the ABR were used to construct an estimate of the armadillo audiogram describing the mean thresholds of the eight animals tested. The majority of animals tested (six out of eight) exhibited clear responses to stimuli from 0.5 to 38 kHz, and two animals exhibited responses to stimuli of 48 kHz. Across all cases, the lowest thresholds were observed for frequencies from 8 to 12 kHz. Overall, we observed that the armadillo estimated audiogram bears a similar pattern as those observed using ABR in members of other mammalian clades, including marsupials and later-derived placental mammals.

Hearing intervention for decreasing risk of developing dementia in elders with mild cognitive impairment: study protocol of a multicenter randomized controlled trial for Chinese Hearing Solution for Improvement of Cognition in Elders (CHOICE)

BACKGROUND

Age-related hearing loss (ARHL) signifies the bilateral, symmetrical, sensorineural hearing loss that commonly occurs in elderly individuals. Several studies have suggested a higher risk of dementia among patients diagnosed with ARHL. Although the precise causal association between ARHL and cognitive decline remains unclear, ARHL has been recognized as one of the most significant factors that can be modified to reduce the risk of developing dementia potentially. Mild cognitive impairment (MCI) typically serves as the initial stage in the transition from normal cognitive function to dementia. Consequently, the objective of our randomized controlled trial (RCT) is to further investigate whether the use of hearing aids can enhance cognitive function in older adults diagnosed with ARHL and MCI.

METHODS AND DESIGN

This study is a parallel-arm, randomized controlled trial conducted at multiple centers in Shanghai, China. We aim to enlist a total of 688 older adults (age ≥ 60) diagnosed with moderate-to-severe ARHL and MCI from our four research centers. Participants will be assigned randomly to either the hearing aid fitting group or the health education group using block randomization with varying block sizes. Audiometry, cognitive function assessments, and other relevant data will be collected at baseline, as well as at 6, 12, and 24 months post-intervention by audiologists and trained researchers. The primary outcome of our study is the rate of progression to dementia among the two groups of participants. Additionally, various evaluations will be conducted to measure hearing improvement and changes in cognitive function. Apart from the final study results, we also plan to conduct an interim analysis using data from 12-month follow-up.

DISCUSSION

In recent years, there has been a notable lack of randomized controlled trials (RCTs) investigating the possible causal relationship between hearing fitting and the improvement of cognitive function. Our findings may demonstrate that hearing rehabilitation can be a valuable tool in managing ARHL and preventing cognitive decline, which will contribute to the development of a comprehensive framework for the prevention and control of cognitive decline.

TRIAL REGISTRATION

Chinese Clinical Trial Registry chictr.org.cn ChiCTR2000036139. Registered on 21 August 2020.

Sheep as a large animal model for hearing research: comparison to common laboratory animals and humans

Sensorineural hearing loss (SNHL), caused by pathology in the cochlea, is the most common type of hearing loss in humans. It is generally irreversible with very few effective pharmacological treatments available to prevent the degenerative changes or minimise the impact. Part of this has been attributed to difficulty of translating "proof-of-concept" for novel treatments established in small animal models to human therapies. There is an increasing interest in the use of sheep as a large animal model. In this article, we review the small and large animal models used in pre-clinical hearing research such as mice, rats, chinchilla, guinea pig, rabbit, cat, monkey, dog, pig, and sheep to humans, and compare the physiology, inner ear anatomy, and some of their use as model systems for SNHL, including cochlear implantation surgeries. Sheep have similar cochlear anatomy, auditory threshold, neonatal auditory system development, adult and infant body size, and number of birth as humans. Based on these comparisons, we suggest that sheep are well-suited as a potential translational animal model that bridges the gap between rodent model research to the clinical use in humans. This is especially in areas looking at changes across the life-course or in specific areas of experimental investigation such as cochlear implantation and other surgical procedures, biomedical device development and age-related sensorineural hearing loss research. Combined use of small animals for research that require higher throughput and genetic modification and large animals for medical translation could greatly accelerate the overall translation of basic research in the field of auditory neuroscience from bench to clinic.

Genetic analysis of potential biomarkers and therapeutic targets in age-related hearing loss

Age-related hearing loss (ARHL) or presbycusis is the phenomenon of hearing loss due to the aging of auditory organs with age. It seriously affects the cognitive function and quality of life of the elderly. This study is based on comprehensive bioinformatic and machine learning methods to identify the critical genes of ARHL and explore its therapy targets and pathological mechanisms. The ARHL and normal samples were from GSE49543 datasets of the Gene Expression Omnibus (GEO) database. Weighted gene co-expression network analysis (WGCNA) was applied to obtain significant modules. The Limma R-package was used to identify differentially expressed genes (DEGs). The 15 common genes of the practical module and DEGs were screened. Functional enrichment analysis suggested that these genes were mainly associated with inflammation, immune response, and infection. Cytoscape software created the protein-protein interaction (PPI) layouts and cytoHubba, support vector machine-recursive feature elimination (SVM-RFE), and random forests (RF) algorithms screened hub genes. After validating the hub gene expressions in GSE6045 and GSE154833 datasets, Clec4n, Mpeg1, and Fcgr3 are highly expressed in ARHL and have higher diagnostic efficacy for ARHL, so they were identified as hub genes. In conclusion, Clec4n, Mpeg1, and Fcgr3 play essential roles in developing ARHL, and they might become vital targets in ARHL diagnosis and anti-inflammatory therapy.

Comprehensive Transcriptomic Profiling of m6A Modification in Age-Related Hearing Loss

Age-related hearing loss (ARHL), also known as presbycusis, is one of the most common neurodegenerative disorders in elderly individuals and has a prevalence of approximately 70-80% among individuals aged 65 and older. As ARHL is an intricate and multifactorial disease, the exact pathogenesis of ARHL is not fully understood. There is evidence that transcriptional dysregulation mediated by epigenetic modifications is widespread in ARHL. However, the potential role of N6-methyladenosine (m6A) modification, as a crucial component of epigenetics, in ARHL progression remains unclear. In this study, we confirmed that the downregulation of m6A modification in cochlear tissues is related to ARHL and found that the expression of the m6A methylation regulators Wilms tumour suppressor-1-associated protein (WTAP), methyltransferase-like 3 (METTL3), ALKB homologous protein 5 (ALKBH5) and fat mass and obesity-associated protein (FTO) is decreased significantly at the mRNA and protein levels in ARHL mice. Then, we used methylated RNA immunoprecipitation sequencing (MeRIP-Seq) and RNA sequencing (RNA-Seq) to identify the differentially m6A-methylated genes in the cochlear tissues of ARHL mice. A total of 3438 genes with differential m6A methylation were identified, of which 1332 genes were m6A-hypermethylated and 2106 genes were m6A-hypomethylated in the ARHL group compared to the control group according to MeRIP-seq. Further joint analysis of RNA-Seq and MeRIP-Seq data showed that 262 genes had significant differences in both mRNA expression and m6A methylation. GO and KEGG analyses indicated that 262 unique genes were enriched mainly in the PI3K-AKT signalling pathway. In conclusion, the results of this study reveal differential m6A methylation patterns in the cochlear tissues of ARHL mice, providing a theoretical basis for further study of the pathogenesis of ARHL and potential therapeutic strategies.

Influence of Age on Speech Recognition in Noise and Hearing Effort in Listeners with Age-Related Hearing Loss

The aim of this study was to measure how age affects the speech recognition threshold (SRT50) of the Oldenburg Sentence Test (OLSA) and the listening effort at the corresponding signal-to-noise ratio (SNRcut). The study also investigated the effect of the spatial configuration of sound sources and noise signals on SRT50 and SNRcut. To achieve this goal, the study used olnoise and icra5 noise presented from one or more spatial locations from the front and back. Ninety-nine participants with age-related hearing loss in the 18-80 years age range, specifically in the 18-30, 31-40, 41-50, 51-60, 61-70, and 71-80 age groups, participated in this study. Speech recognition and listening effort in noise were measured and compared between the different age groups, different spatial sound configurations and noise signals. Speech recognition in noise decreased with age and became significant from the age group of 50-51. The decrease in SRT50 with age was greater for icra5 noise than for olnoise. For all age groups, SRT50 and SNRcut were better for icra5 noise than for olnoise. The measured age-related reference data for SRT50 and SNRcut can be used in further studies in listeners with age-related hearing loss and hearing aid or implant users.

Age-related hearing loss and its potential drug candidates: a systematic review

BACKGROUND

Age-related hearing loss (ARHL) is one of the main illnesses afflicting the aged population and has a significant negative impact on society, economy, and health. However, there is presently no appropriate therapeutic treatment of ARHL due to the absence of comprehensive trials.

OBJECTIVES

The goal of this review is to systematically evaluate and analyze recent statistics on the pathologic classifications, risk factors, treatment strategies, and drug candidates of ARHL, including that from traditional Chinese medicine (TCM), to provide potential new approaches for preventing and treating ARHL.

METHODS

Literature related to ARHL was conducted in databases such as PubMed, WOS, China National Knowledge Infrastructure (CNKI), and Wanfang from the establishment of the database to Jan, 2023. The pathology, causal factor, pathophysiological mechanism, treatment strategy, and the drug candidate of ARHL were extracted and pooled for synthesis.

RESULTS

Many hypotheses about the etiology of ARHL are based on genetic and environmental elements. Most of the current research on the pathology of ARHL focuses on oxidative damage, mitochondrial dysfunction, inflammation, cochlear blood flow, ion homeostasis, etc. In TCM, herbs belonging to the kidney, lung, and liver meridians exhibit good hearing protection. Seven herbs belonging to the kidney meridian, 9 belonging to the lung meridian, and 4 belonging to the liver meridian were ultimately retrieved in this review, such as Polygonum multiflorum Thunb., Panax ginseng C.A. Mey, and Pueraria lobata (Willd.) Ohwi. Their active compounds, 2,3,4',5-Tetrahydroxystilbene-2-O-D-glucoside, ginsenoside Rb1, and puerarin, may act as the molecular substance for their anti-ARHL efficacy, and show anti-oxidative, neuroprotective, anti-inflammatory, anti-apoptotic, or mitochondrial protective effects.

CONCLUSION

Anti-oxidants, modulators of mitochondrial function, anti-inflammation agents, vasodilators, K+ channel openers, Ca2+ channel blockers, JNK inhibitors, and nerve growth factors/neurotrophic factors all contribute to hearing protection, and herbs are an important source of potential anti-ARHL drugs.

Progress on mechanisms of age-related hearing loss

Age-related hearing loss, or presbycusis, is a common cause of hearing loss in elderly people worldwide. It typically presents as progressive, irreversible, and usually affects the high frequencies of hearing, with a tremendous impact on the quality of life. Presbycusis is a complex multidimensional disorder, in addition to aging, multiple factors including exposure to noise, or ototoxic agents, genetic susceptibility, metabolic diseases and lifestyle can influence the onset and severity of presbycusis. With the aging of the body, its ability to clean up deleterious substances produced in the metabolic process is weakened, and the self-protection and repair function of the body is reduced, which in turn leads to irreversible damage to the cochlear tissue, resulting in the occurrence of presbycusis. Presently, oxidative stress (OS), mitochondrial DNA damage, low-grade inflammation, decreased immune function and stem cell depletion have been demonstrated to play a critical role in developing presbycusis. The purpose of this review is to illuminate the various mechanisms underlying this age-related hearing loss, with the goal of advancing our understanding, prevention, and treatment of presbycusis.

Is Hearing Loss a Risk Factor for Idiopathic Parkinson's Disease? An English Longitudinal Study of Ageing Analysis

Observations that hearing loss is a substantial risk factor for dementia may be accounted for by a common pathology. Mitochondrial oxidative stress and alterations in α-synuclein pathology may be common pathology candidates. Crucially, these candidate pathologies are implicated in Parkinson's disease (PD). Consequently, hearing loss may be a risk factor for PD. Subsequently, this prospective cohort study of the English Longitudinal Study of Ageing examines whether hearing loss is a risk factor for PD longitudinally. Participants reporting self-reported hearing capabilities and no PD diagnosis prior to entry (n = 14,340) were used. A joint longitudinal and survival model showed that during a median follow up of 10 years (SD = 4.67 years) increased PD risk (p < 0.001), but not self-reported hearing capability (p = 0.402). Additionally, an exploratory binary logistic regression modelling the influence of hearing loss identified using a screening test (n = 4812) on incident PD indicated that neither moderate (p = 0.794), nor moderately severe/severe hearing loss (p = 0.5210), increased PD risk, compared with normal hearing. Whilst discrepancies with prior literature may suggest a neurological link between hearing loss and PD, further large-scale analyses using clinically derived hearing loss are needed.

The Stria Vascularis in Mice and Humans Is an Early Site of Age-Related Cochlear Degeneration, Macrophage Dysfunction, and Inflammation

Age-related hearing loss, or presbyacusis, is a common degenerative disorder affecting communication and quality of life for millions of older adults. Multiple pathophysiologic manifestations, along with many cellular and molecular alterations, have been linked to presbyacusis; however, the initial events and causal factors have not been clearly established. Comparisons of the transcriptome in the lateral wall (LW) with other cochlear regions in a mouse model (of both sexes) of "normal" age-related hearing loss revealed that early pathophysiological alterations in the stria vascularis (SV) are associated with increased macrophage activation and a molecular signature indicative of inflammaging, a common form of immune dysfunction. Structure-function correlation analyses in mice across the lifespan showed that the age-dependent increase in macrophage activation in the stria vascularis is associated with a decline in auditory sensitivity. High-resolution imaging analysis of macrophage activation in middle-aged and aged mouse and human cochleas, along with transcriptomic analysis of age-dependent changes in mouse cochlear macrophage gene expression, support the hypothesis that aberrant macrophage activity is an important contributor to age-dependent strial dysfunction, cochlear pathology, and hearing loss. Thus, this study highlights the SV as a primary site of age-related cochlear degeneration and aberrant macrophage activity and dysregulation of the immune system as early indicators of age-related cochlear pathology and hearing loss. Importantly, novel new imaging methods described here now provide a means to analyze human temporal bones in a way that had not previously been feasible and thereby represent a significant new tool for otopathological evaluation.SIGNIFICANCE STATEMENT Age-related hearing loss is a common neurodegenerative disorder affecting communication and quality of life. Current interventions (primarily hearing aids and cochlear implants) offer imperfect and often unsuccessful therapeutic outcomes. Identification of early pathology and causal factors is crucial for the development of new treatments and early diagnostic tests. Here, we find that the SV, a nonsensory component of the cochlea, is an early site of structural and functional pathology in mice and humans that is characterized by aberrant immune cell activity. We also establish a new technique for evaluating cochleas from human temporal bones, an important but understudied area of research because of a lack of well-preserved human specimens and difficult tissue preparation and processing approaches.

Mitochondrial alterations in the cochlea of Cdk5rap1-knockout mice with age-related hearing loss

Previous studies have revealed that age-related hearing loss (AHL) in Cdk5 regulatory subunit-associated protein 1 (Cdk5rap1)-knockout mice is associated with pathology in the cochlea. Here, we aimed to identify mitochondrial alterations in the cochlea of Cdk5rap1-knockout mice with AHL. Mitochondria in the spiral ganglion neurons (SGNs) and hair cells (HCs) were normal despite senescence; however, the mitochondria of types I, II, and IV spiral ligament fibrocytes were ballooned, damaged, and ballooned, respectively, in the stria vascularis. Our results suggest that the accumulation of dysfunctional mitochondria in the lateral wall, rather than the loss of HCs and SGNs, leads to the onset of AHL. Our results provide valuable information regarding the underlying mechanisms of AHL and the relationship between aberrant tRNA modification-induced hearing loss and mitochondrial dysfunction.

Pharmacological Modulation of Energy and Metabolic Pathways Protects Hearing in the Fus1/Tusc2 Knockout Model of Mitochondrial Dysfunction and Oxidative Stress

Tightly regulated and robust mitochondrial activities are critical for normal hearing. Previously, we demonstrated that Fus1/Tusc2 KO mice with mitochondrial dysfunction exhibit premature hearing loss. Molecular analysis of the cochlea revealed hyperactivation of the mTOR pathway, oxidative stress, and altered mitochondrial morphology and quantity, suggesting compromised energy sensing and production. Here, we investigated whether the pharmacological modulation of metabolic pathways using rapamycin (RAPA) or 2-deoxy-D-glucose (2-DG) supplementation can protect against hearing loss in female Fus1 KO mice. Additionally, we aimed to identify mitochondria- and Fus1/Tusc2-dependent molecular pathways and processes critical for hearing. We found that inhibiting mTOR or activating alternative mitochondrial energetic pathways to glycolysis protected hearing in the mice. Comparative gene expression analysis revealed the dysregulation of critical biological processes in the KO cochlea, including mitochondrial metabolism, neural and immune responses, and the cochlear hypothalamic-pituitary-adrenal axis signaling system. RAPA and 2-DG mostly normalized these processes, although some genes showed a drug-specific response or no response at all. Interestingly, both drugs resulted in a pronounced upregulation of critical hearing-related genes not altered in the non-treated KO cochlea, including cytoskeletal and motor proteins and calcium-linked transporters and voltage-gated channels. These findings suggest that the pharmacological modulation of mitochondrial metabolism and bioenergetics may restore and activate processes critical for hearing, thereby protecting against hearing loss.

Bats experience age-related hearing loss (presbycusis)

Hearing loss is a hallmark of aging, typically initially affecting the higher frequencies. In echolocating bats, the ability to discern high frequencies is essential. However, nothing is known about age-related hearing loss in bats, and they are often assumed to be immune to it. We tested the hearing of 47 wild Egyptian fruit bats by recording their auditory brainstem response and cochlear microphonics, and we also assessed the cochlear histology in four of these bats. We used the bats' DNA methylation profile to evaluate their age and found that bats exhibit age-related hearing loss, with more prominent deterioration at the higher frequencies. The rate of the deterioration was ∼1 dB per year, comparable to the hearing loss observed in humans. Assessing the noise in the fruit bat roost revealed that these bats are exposed to continuous immense noise-mostly of social vocalizations-supporting the assumption that bats might be partially resistant to loud noise. Thus, in contrast to previous assumptions, our results suggest that bats constitute a model animal for the study of age-related hearing loss.

MiR-29a-deficiency causes thickening of the basilar membrane and age-related hearing loss by upregulating collagen IV and laminin

Age-related hearing loss (ARHL) is the most common sensory degenerative disease and can significantly impact the quality of life in elderly people. A previous study using GeneChip miRNA microarray assays showed that the expression of miR-29a changes with age, however, its role in hearing loss is still unclear. In this study, we characterized the cochlear phenotype of miR-29a knockout (miR-29a^-/-) mice and found that miR-29a-deficient mice had a rapid progressive elevation of the hearing threshold from 2 to 5 months of age compared with littermate controls as measured by the auditory brainstem response. Stereocilia degeneration, hair cell loss and abnormal stria vascularis (SV) were observed in miR-29a^-/- mice at 4 months of age. Transcriptome sequencing results showed elevated extracellular matrix (ECM) gene expression in miR-29a^-/- mice. Both Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that the key differences were closely related to ECM. Further examination with a transmission electron microscope showed thickening of the basilar membrane in the cochlea of miR-29a^-/- mice. Five Col4a genes (Col4a1-a5) and two laminin genes (Lamb2 and Lamc1) were validated as miR-29a direct targets by dual luciferase assays and miR-29a inhibition assays with a miR-29a inhibitor. Consistent with the target gene validation results, the expression of these genes was significantly increased in the cochlea of miR-29a^-/- mice, as shown by RT-PCR and Western blot. These findings suggest that miR-29a plays an important role in maintaining cochlear structure and function by regulating the expression of collagen and laminin and that the disturbance of its expression could be a cause of progressive hearing loss.

Listening with an Ageing Brain - a Cognitive Challenge

Hearing impairment has been recently identified as a major modifiable risk factor for cognitive decline in later life and has been becoming of increasing scientific interest. Sensory and cognitive decline are connected by complex bottom-up and top-down processes, a sharp distinction between sensation, perception, and cognition is impossible. This review provides a comprehensive overview on the effects of healthy and pathological aging on auditory as well as cognitive functioning on speech perception and comprehension, as well as specific auditory deficits in the 2 most common neurodegenerative diseases in old age: Alzheimer disease and Parkinson syndrome. Hypotheses linking hearing loss to cognitive decline are discussed, and current knowledge on the effect of hearing rehabilitation on cognitive functioning is presented. This article provides an overview of the complex relationship between hearing and cognition in old age.

Regeneration of Hair Cells from Endogenous Otic Progenitors in the Adult Mammalian Cochlea: Understanding Its Origins and Future Directions

Sensorineural hearing loss is caused by damage to sensory hair cells and/or spiral ganglion neurons. In non-mammalian species, hair cell regeneration after damage is observed, even in adulthood. Although the neonatal mammalian cochlea carries regenerative potential, the adult cochlea cannot regenerate lost hair cells. The survival of supporting cells with regenerative potential after cochlear trauma in adults is promising for promoting hair cell regeneration through therapeutic approaches. Targeting these cells by manipulating key signaling pathways that control mammalian cochlear development and non-mammalian hair cell regeneration could lead to regeneration of hair cells in the mammalian cochlea. This review discusses the pathways involved in the development of the cochlea and the impact that trauma has on the regenerative capacity of the endogenous progenitor cells. Furthermore, it discusses the effects of manipulating key signaling pathways targeting supporting cells with progenitor potential to promote hair cell regeneration and translates these findings to the human situation. To improve hearing recovery after hearing loss in adults, we propose a combined approach targeting (1) the endogenous progenitor cells by manipulating signaling pathways (Wnt, Notch, Shh, FGF and BMP/TGFβ signaling pathways), (2) by manipulating epigenetic control, and (3) by applying neurotrophic treatments to promote reinnervation.

Piceatannol protects against age-related hearing loss by inhibiting cellular pyroptosis and inflammation through regulated Caspase11-GSDMD pathway

Age-related hearing loss (ARHL) is a common issue associated with aging. One of the typical causes of hearing loss is the damage to inner ear hair cells. In addition, oxidative stress and inflammation contribute to ARHL. To avoid excessive inflammatory responses, non-classical scorch death pathway by cell membrane lipopolysaccharide (LPS) activates of caspase-11. Piceatannol (PCT) is also known for anti-tumor, antioxidant and anti-inflammatory effects; however, the protective effect of piceatannol (PCT) on ARHL is unclear. The aim of this study was to elucidate the mechanism underlying protective effect of PCT on ARHL-induced inner ear hair cell damage. In vivo experiments showed that PCT could protect mice from inflammatory aging-induced hearing loss as well as from inner hair cells (IHC) and spiral ganglion (SG) deficits. In addition, inflammatory vesicle inhibitor BAY11-7082 ameliorated ARHL, inhibited NLRP3 and reduced GSDMD expression. In in vitro experiments we used LPS and D-gal to simulate the aging inflammatory environment. The results showed that intracellular reactive oxygen species levels, expression of Caspase-11, NLRP3, and GSDMD were significantly increased, yet treatment with PCT or BAY11-7082 significantly improved HEI-OC-1 cell injury while reducing inflammation-associated protein expression as well as the occurrence of pyroptosis. In conclusion, these results suggest a protective role for PCT against ARHL, possibly through Caspase-11-GSDMD pathway. Our findings may provide a new target and theoretical basis for hearing loss treatment using PCT.

Stability of neural representations in the auditory midbrain across the lifespan despite age-related brainstem delays

The extent to which aging of the central auditory pathway impairs auditory perception in the elderly independent of peripheral cochlear decline is debated. To cause auditory deficits in normal hearing elderly, central aging needs to degrade neural sound representations at some point along the auditory pathway. However, inaccessible to psychophysical methods, the level of the auditory pathway at which aging starts to effectively degrade neural sound representations remains poorly differentiated. Here we tested how potential age-related changes in the auditory brainstem affect the stability of spatiotemporal multiunit complex speech-like sound representations in the auditory midbrain of old normal hearing CBA/J mice. Although brainstem conduction speed slowed down in old mice, the change was limited to the sub-millisecond range and only minimally affected temporal processing in the midbrain (i.e. gaps-in-noise sensitivity). Importantly, besides the small delay, multiunit complex temporal sound representations in the auditory midbrain did not differ between young and old mice. This shows that although small age-related neural effects in simple sound parameters in the lower brainstem may be present in aging they do not effectively deteriorate complex neural population representations at the level of the auditory midbrain when peripheral hearing remains normal. This result challenges the widespread belief of 'pure' central auditory decline as an automatic consequence of aging, at least up to the inferior colliculus. However, the stability of midbrain processing in aging emphasizes the role of undetected 'hidden' peripheral damage and accumulating effects in higher cortical auditory-cognitive processing explaining perception deficits in 'normal hearing' elderly.

Noise Exposure in Palestinian Workers Without a Diagnosis of Hearing Impairment: Relations to Speech-Perception-in-Noise Difficulties, Tinnitus, and Hyperacusis

PURPOSE

Many workers in developing countries are exposed to unsafe occupational noise due to inadequate health and safety practices. We tested the hypotheses that occupational noise exposure and aging affect speech-perception-in-noise (SPiN) thresholds, self-reported hearing ability, tinnitus presence, and hyperacusis severity among Palestinian workers.

METHOD

Palestinian workers (N = 251, aged 18-70 years) without diagnosed hearing or memory impairments completed online instruments including a noise exposure questionnaire; forward and backward digit span tests; hyperacusis questionnaire; the short-form Speech, Spatial and Qualities of Hearing Scale (SSQ12); the Tinnitus Handicap Inventory; and a digits-in-noise (DIN) test. Hypotheses were tested via multiple linear and logistic regression models, including age and occupational noise exposure as predictors, and with sex, recreational noise exposure, cognitive ability, and academic attainment as covariates. Familywise error rate was controlled across all 16 comparisons using the Bonferroni-Holm method. Exploratory analyses evaluated effects on tinnitus handicap. A comprehensive study protocol was preregistered.

RESULTS

Nonsignificant trends of poorer SPiN performance, poorer self-reported hearing ability, greater prevalence of tinnitus, greater tinnitus handicap, and greater severity of hyperacusis as a function of higher occupational noise exposure were observed. Greater hyperacusis severity was significantly predicted by higher occupational noise exposure. Aging was significantly associated with higher DIN thresholds and lower SSQ12 scores, but not with tinnitus presence, tinnitus handicap, or hyperacusis severity.

CONCLUSIONS

Workers in Palestine may suffer from auditory effects of occupational noise and aging despite no formal diagnosis. These findings highlight the importance of occupational noise monitoring and hearing-related health and safety practices in developing countries.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.22056701.

Age-Related Hearing Loss, Cognitive Performance, and Metabolic Risk in Healthy Adults: A Seven-Year Longitudinal Study

OBJECTIVES

Sensorineural hearing loss (presbycusis) affects up to half of the adults, is associated with cognitive decline. Whether this association reflects the cause, the consequence, or parallel processes driven by other factors remains unclear. Both presbycusis and cognition are linked to elevated metabolic risk, which in turn raises with age.

METHOD

In a multioccasion longitudinal design, we used latent change score models with strong factorial invariance to assess the change in pure-tone threshold auditory function, fluid intelligence, metabolic risk, variability therein, and the dynamic relationships among the 3 domains. We examined, up to 4 times over more than 7 years, a sample of relatively healthy 687 adults (aged 18.17-83.25 years).

RESULTS

We found that levels of auditory and cognitive functioning at time t-1 influence each other's subsequent change between times t-1 and t, even when controlling for the reciprocal effects of metabolic risk on both. Thus, auditory and cognitive functioning do not only decline in parallel in healthy adults, but also affect each other's trajectories. To the best of our knowledge, this is the first long-term study with such evidence.

DISCUSSION

Our results are in accord with extant hypotheses about auditory-cognitive associations in old age (e.g., social isolation, cognitive load, increased inflammation, reduced gene expression, and other microvascular or neuropathological factors). They also echo previous reports underscoring the need for improving access to hearing aids and other rehabilitative services aimed at reducing hearing loss. If applied early in the aging process, such interventions may mitigate cognitive decline.

Noise-induced auditory damage affects hippocampus causing memory deficits in a model of early age-related hearing loss

Several studies identified noise-induced hearing loss (NIHL) as a risk factor for sensory aging and cognitive decline processes, including neurodegenerative diseases, such as dementia and age-related hearing loss (ARHL). Although the association between noise- and age-induced hearing impairment has been widely documented by epidemiological and experimental studies, the molecular mechanisms underlying this association are not fully understood as it is not known how these risk factors (aging and noise) can interact, affecting memory processes. We recently found that early noise exposure in an established animal model of ARHL (C57BL/6 mice) accelerates the onset of age-related cochlear dysfunctions. Here, we extended our previous data by investigating what happens in central brain structures (auditory cortex and hippocampus), to assess the relationship between hearing and memory impairment and the possible combined effect of noise and sensory aging on the cognitive domain. To this aim, we exposed juvenile C57BL/6 mice of 2 months of age to repeated noise sessions (60 min/day, pure tone of 100 dB SPL, 10 kHz, 10 consecutive days) and we monitored auditory threshold by measuring auditory brainstem responses (ABR), spatial working memory, by using the Y-maze test, and basal synaptic transmission by using ex vivo electrophysiological recordings, at different time points (1, 4 and 7 months after the onset of noise exposure, corresponding to 3, 6 and 9 months of age). We found that hearing loss, along with accelerated presbycusis onset, can induce persistent synaptic alterations in the auditory cortex. This was associated with decreased memory performance and oxidative-inflammatory injury in the hippocampus, the extra-auditory structure involved in memory processes. Collectively, our data confirm the critical relationship between auditory and memory circuits, suggesting that the combined detrimental effect of noise and sensory aging on hearing function can be considered a high-risk factor for both sensory and cognitive degenerative processes, given that early noise exposure accelerates presbycusis phenotype and induces hippocampal-dependent memory dysfunctions.

Promoting TFEB nuclear localization with curcumin analog C1 attenuates sensory hair cell injury and delays age-related hearing loss in C57BL/6 mice

Sensory hair cell (HC) injuries, especially outer hair cell (OHC) loss, are well-documented to be the primary pathology of age-related hearing loss (AHL). Recent studies have demonstrated that autophagy plays an important role in HC injury in the inner ear. In our previous works, a decline in autophagy levels and HC loss were found to occur simultaneously in the inner ears of aged C57BL/6 mice, and the administration of rapamycin promoted autophagy levels, which reduced OHC loss and delayed AHL, but the underlying mechanism of autophagy in AHL has not been well elucidated. Transcription factor EB (TFEB), an autophagy regulator and the downstream target of mammalian target of rapamycin (mTOR), is involved in the pathological development of neurodegenerative disease. This study would address the link between autophagy and TFEB in aged C57BL/6 mouse cochleae and clarify the effect of the TFEB activator curcumin analog C1 (C1) in aged cochleae. Decreased TFEB nuclear localization (p = 0.0371) and autophagy dysfunction (p = 0.0273) were observed in the cochleae of aged C57BL/6 mice that exhibited AHL, HCs loss and HCs senescence. Treatment with C1 promoted TFEB nuclear localization and restored autophagy, subsequently alleviating HC injury and delaying AHL. The protective effect of C1 on HEI-OC1 cells against autophagy disorder and aging induced by D-galactose was abolished by chloroquine, which is one of the commonly used autophagy inhibitors. Overall, our results demonstrated that the capacity to perform autophagy is mediated by the nuclear localization of TFEB in aged C57BL/6 mouse cochleae. C1 promotes the nuclear localization of TFEB, subsequently alleviating HC injury and delaying AHL by restoring the impaired autophagy function. TFEB may serve as a new therapeutic target for AHL treatment.

Plasticity After Hearing Rehabilitation in the Aging Brain

Age-related hearing loss, presbycusis, is an unavoidable sensory degradation, often associated with the progressive decline of cognitive and social functions, and dementia. It is generally considered a natural consequence of the inner-ear deterioration. However, presbycusis arguably conflates a wide array of peripheral and central impairments. Although hearing rehabilitation maintains the integrity and activity of auditory networks and can prevent or revert maladaptive plasticity, the extent of such neural plastic changes in the aging brain is poorly appreciated. By reanalyzing a large-scale dataset of more than 2200 cochlear implant users (CI) and assessing the improvement in speech perception from 6 to 24 months of use, we show that, although rehabilitation improves speech understanding on average, age at implantation only minimally affects speech scores at 6 months but has a pejorative effect at 24 months post implantation. Furthermore, older subjects (>67 years old) were significantly more likely to degrade their performances after 2 years of CI use than the younger patients for each year increase in age. Secondary analysis reveals three possible plasticity trajectories after auditory rehabilitation to account for these disparities: Awakening, reversal of deafness-specific changes; Counteracting, stabilization of additional cognitive impairments; or Decline, independent pejorative processes that hearing rehabilitation cannot prevent. The role of complementary behavioral interventions needs to be considered to potentiate the (re)activation of auditory brain networks.

CAPRIN1 haploinsufficiency causes a neurodevelopmental disorder with language impairment, ADHD and ASD

We describe an autosomal dominant disorder associated with loss-of-function variants in the Cell cycle associated protein 1 (CAPRIN1; MIM*601178). CAPRIN1 encodes a ubiquitous protein that regulates the transport and translation of neuronal mRNAs critical for synaptic plasticity, as well as mRNAs encoding proteins important for cell proliferation and migration in multiple cell types. We identified 12 cases with loss-of-function CAPRIN1 variants, and a neurodevelopmental phenotype characterized by language impairment/speech delay (100%), intellectual disability (83%), attention deficit hyperactivity disorder (82%) and autism spectrum disorder (67%). Affected individuals also had respiratory problems (50%), limb/skeletal anomalies (50%), developmental delay (42%) feeding difficulties (33%), seizures (33%) and ophthalmologic problems (33%). In patient-derived lymphoblasts and fibroblasts, we showed a monoallelic expression of the wild-type allele, and a reduction of the transcript and protein compatible with a half dose. To further study pathogenic mechanisms, we generated sCAPRIN1+/- human induced pluripotent stem cells via CRISPR-Cas9 mutagenesis and differentiated them into neuronal progenitor cells and cortical neurons. CAPRIN1 loss caused reduced neuronal processes, overall disruption of the neuronal organization and an increased neuronal degeneration. We also observed an alteration of mRNA translation in CAPRIN1+/- neurons, compatible with its suggested function as translational inhibitor. CAPRIN1+/- neurons also showed an impaired calcium signalling and increased oxidative stress, two mechanisms that may directly affect neuronal networks development, maintenance and function. According to what was previously observed in the mouse model, measurements of activity in CAPRIN1+/- neurons via micro-electrode arrays indicated lower spike rates and bursts, with an overall reduced activity. In conclusion, we demonstrate that CAPRIN1 haploinsufficiency causes a novel autosomal dominant neurodevelopmental disorder and identify morphological and functional alterations associated with this disorder in human neuronal models.

Pyroptosis and degenerative diseases of the elderly

Pyroptosis is a recently described mechanism of programmed cell death mediated by proteins of the gasdermin family. Widely recognized signaling cascades include the classical, non-classical, caspase-3-dependent gasdermin E and caspase-8-dependent gasdermin D pathways. Additional pyroptotic pathways have been subsequently reported. With the rising prevalence of advanced age, the role of pyroptosis in the degenerative diseases of the elderly has attracted increased research attention. This article reviews the primary mechanisms of pyroptosis and summarizes progress in the research of degenerative diseases of the elderly such as presbycusis, age-related macular degeneration, Alzheimer's disease, intervertebral disc degeneration, and osteoarthritis.

The role of the stria vascularis in neglected otologic disease

The stria vascularis (SV) has been shown to play a critical role in the pathogenesis of many diseases associated with sensorineural hearing loss (SNHL), including age-related hearing loss (ARHL), noise-induced hearing loss (NIHL), hereditary hearing loss (HHL), and drug-induced hearing loss (DIHL), among others. There are a number of other disorders of hearing loss that may be relatively neglected due to being underrecognized, poorly understood, lacking robust diagnostic criteria or effective treatments. A few examples of these diseases include autoimmune inner ear disease (AIED) and/or autoinflammatory inner ear disease (AID), Meniere's disease (MD), sudden sensorineural hearing loss (SSNHL), and cytomegalovirus (CMV)-related hearing loss (CRHL). Although these diseases may often differ in etiology, there have been recent studies that support the involvement of the SV in the pathogenesis of many of these disorders. We strive to highlight a few prominent examples of these frequently neglected otologic diseases and illustrate the relevance of understanding SV composition, structure and function with regards to these disease processes. In this study, we review the physiology of the SV, lay out the importance of these neglected otologic diseases, highlight the current literature regarding the role of the SV in these disorders, and discuss the current strategies, both approved and investigational, for management of these disorders.

Hearing and Ageing

Age-related hearing loss (ARHL), or presbycusis, occurs in most mammals, humans included, with a different age of onset and magnitude of loss. It is associated with two major symptoms: loss of sensitivity to sound, especially for high pitches, and a reduced ability to understand speech in background noise. This phenomenon involves both the peripheral structures of the inner ear and the central acoustic pathways. Several mechanisms have been identified as pro-ageing in the human cochlea. The main one is the oxidative stress. The inner ear physiological degeneration can be affected by both intrinsic conditions, such as genetic predisposition, and extrinsic ones, such as noise exposure. The magnitude of neuronal loss precedes and exceeds that of inner hair cell loss, which is also less important than the loss of outer hair cells. Patients with HL often develop atrophy of the temporal lobe (auditory cortex) and brain gliosis can contribute to the development of a central hearing loss. The presence of white matter hyperintensities (WMHs) on the MRI, which is radiologic representation of brain gliosis, can justify a central HL due to demyelination in the superior auditory pathways. Recently, the presence of WMHs has been correlated with the inability to correctly understand words in elderly with normal auditory thresholds.

Spatial architecture of the cochlear immune microenvironment in noise-induced and age-related sensorineural hearing loss

The cochlea encodes sound stimuli and transmits them to the central nervous system, and damage to sensory cells and synapses in the cochlea leads to hearing loss. The inner ear was previously considered to be an immune privileged organ to protect the auditory organ from reactions with the immune system. However, recent studies have revealed the presence of resident macrophages in the cochlea, especially in the spiral ligament, spiral ganglion, and stria vascularis. The tissue-resident macrophages are responsible for the detection, phagocytosis, and clearance of cellular debris and pathogens from the tissues, and they initiate inflammation and influence tissue repair by producing inflammatory cytokines and chemokines. Insult to the cochlea can activate the cochlear macrophages to initiate immune responses. In this review, we describe the distribution and functions of cochlear macrophages in noise-induced hearing impairment and age-related hearing disabilities. We also focus on potential therapeutic interventions concerning hearing loss by modulating local immune responses.