ABR/DPOAE publications

Damage to the cochlear outer hair cell (OHC) is a major cause of deafness in mammals. OHCs amplify the auditory signals to enhance the sensitivity and sound frequency selectivity of the auditory system. However, detailed mechanisms underlying functional OHC regulation remain unclear. Here, it is demonstrated that volume‐regulated anion channels (VRACs) are essential for OHC function. VRAC subunits are highly expressed in OHCs. Genetic deletion of leucin‐rich repeat containing 8A (LRRC8A), the obligatory VRAC subunit, in hair cells results in hearing loss, whereas re‐expressing LRRC8A in the cochlea restores hearing in LRRC8A‐deficient mice. By employing patch‐clamp electrophysiology, it is shown that VRAC in OHCs is activated by hypotonicity and is involved in regulating cell volume. Furthermore, the nonlinear capacitance (NLC), a measure of electromotility, is decreased in the OHCs from LRRC8A‐deficient mice. Therefore, LRRC8A deficiency compromises electromotility of OHCs and impairs signal amplification. In conclusion, the findings highlight the essential role of VRAC in OHC electromotility and its necessity for auditory function.

Age-related hearing loss (ARHL) is the most common sensorineural hearing loss, and the dysfunction of spiral ganglion neurons (SGNs) and ribbon synapses plays a crucial role in the pathogenesis. The fibroblast growth factor 13 (FGF13) is considered to be associated with neuronal survival and synaptic transmission. However, whether FGF13 is involved in degeneration of SGNs and ribbon synapses, the typical changes of ARHL, is still unknown. Firstly, the expression of FGF13 mRNA and protein, was all dramatically decreased in the SGNs of aged mice, accompanied by impaired SGNs and ribbon synapses. More importantly, specific upregulation of FGF13 in SGNs significantly reduced hearing threshold, improved wave I amplitude, and alleviated loss of SGNs as well as ribbon synapses. Furthermore, the proteomic analysis and verification results suggested that the decrease of FGF13 induced the loss of SGNs and ribbon synapses partly by regulating the ORC1. Taken together, our data revealed that FGF13 might protect SGNs and ribbon synapses by regulating the expression of ORC1, which could provide a new idea and targets for the prevention and treatment of ARHL.

Aminoglycoside antibiotics are essential in managing many life‐threatening diseases. However, their derivatives, such as neomycin, are associated with severe side effects such as persistent sensorineural hearing loss. Therefore, it is essential to elucidate the molecular and biochemical mechanisms of aminoglycoside‐induced ototoxicity and identify targets for alleviating ototoxic injury. Here, we provide a detailed cochlear cell atlas of neomycin‐induced acute and chronic ototoxicity‐related changes through single‐nucleus RNA sequencing profiling. Utilising this cochlear cell atlas, we used the Augur and scDist algorithms to evaluate cell‐type‐specific susceptibility to neomycin injury. We observed aberrant expression of X‐linked inhibitor of apoptosis (Xiap)–associated factor 1 (Xaf1) in neomycin‐exposed cochleae using the cochlear cell atlas, and we identified a novel role for Xaf1 in facilitating PANoptosis through overexpression and knockdown assays in vitro. Finally, we assessed the protective role of Xaf1 against neomycin‐induced ototoxicity by Xaf1 knockdown in cochlear hair cells using adeno‐associated virus‐based gene delivery. Mechanistically, Xaf1 orchestrates PANoptosis activation through direct interaction with and transcriptional regulation of ZBP1, establishing its hierarchical position upstream in the signalling cascade. This study presents detailed cochlear cellular maps of neomycin‐induced ototoxicity and serves as a valuable resource for identifying transcriptome‐wide disease‐driving perturbations at the single‐cell level. More importantly, we identified Xaf1 as a critical target for modulating the PANoptosis pathway, offering a promising treatment strategy for aminoglycoside‐induced ototoxicity.

Noise-induced hearing loss (NIHL) is a widespread auditory disorder in industrialized nations, posing significant global and domestic health concerns. Despite its prevalence, the mechanisms underlying NIHL remain poorly understood, hindering the development of effective therapeutic interventions. Emerging evidence from clinical and animal studies suggests a potential relationship between altered gut microbiota and hearing loss, although causality remains unclear. In this study, we investigated the role of postnatal microbial signals in NIHL pathogenesis using acute noise exposure models in C57BL/6 mice. Our findings indicate that acute noise exposure does not significantly alter gut microbiota composition in this strain and that microbiota depletion does not confer protection against hearing loss following acute acoustic trauma. These results suggest no link between gut microbiota and acute NIHL in C57BL/6 mice.

Age-related hearing loss (ARHL) is one of the most prevalent and complex disorders. Our previous study demonstrated that abnormal activation of mammalian target of rapamycin complex 1 (mTORC1) signaling in the cochlear neurosensory epithelium causes auditory hair cell (HC) damage and contributes to ARHL. However, the underlying mechanism of mTORC1 activation remains unclear. In this study, we identified tumor necrosis factor-alpha-induced protein 8-like 2 (TNFAIP8L2), an immune regulatory gene, as a potential candidate. To elucidate the effect of TNFAIP8L2 on mTORC1 signaling in the neurosensory epithelium and on hearing function, we generated a Tnfaip8l2-deficient (Tnfaip8l2-/-) mouse model. We discovered that Tnfaip8l2 deficiency led to features of oxidative stress in cochlear HCs and age-related hearing degeneration, exhibiting a similar phenotype to the mTORC1-over-activated Tsc1-cKO mice described previously. Furthermore, rapamycin, a well-known mTORC1 inhibitor, significantly mitigated the hearing dysfunction caused by Tnfaip8l2-deficiency. Mechanistically, we found that TNFAIP8L2 regulates mTORC1 signaling by simultaneously inhibiting the GTPase activity of Ras homolog enriched in brain (RHEB) and Ras-related C3 botulinum toxin substrate 1 (RAC1). Notably, both RHEB and RAC1 inhibitors alleviated the hearing phenotype observed in Tnfaip8l2-/- mice by inhibiting mTORC1 signaling. Collectively, our results provide insights into the activation of the mTORC1 pathway in aged mouse cochleae and positions TNFAIP8L2 as a valuable theoretical strategy.

Atypical sensory processing, particularly in the auditory domain, is one of the most common and quality-of-life affecting symptoms seen in autism spectrum disorders (ASD). Fragile X Syndrome (FXS) is a leading inherited cause of ASD and a majority of FXS individuals present with auditory processing alterations. While auditory hypersensitivity is a common phenotype observed in FXS and Fmr1 knockout (KO) rodent models, it is important to consider other auditory coding impairments that could contribute to sound processing difficulties and disrupted language comprehension in FXS. We have shown previously that a Fmr1 KO rat model of FXS exhibits heightened sound sensitivity that coincided with abnormal perceptual integration of stimulus bandwidth, indicative of altered spectral processing. Frequency discrimination is a fundamental aspect of sound encoding that is important for a range of auditory processes, such as source segregation and speech comprehension, and disrupted frequency coding could thus contribute to a range of auditory issues in FXS and ASD. Here we explicitly characterized spectral processing deficits in male Fmr1 KO rats using an operant conditioning tone discrimination assay and in vivo electrophysiological recordings from the auditory cortex and inferior colliculus. We found that Fmr1 KO rats exhibited poorer frequency resolution, which corresponded with neuronal hyperactivity and broader frequency tuning in auditory cortical but not collicular neurons. Using an experimentally informed population model, we show that these cortical physiological differences can recapitulate the observed behavior discrimination deficits, with decoder performance being tightly linked to differences in cortical tuning width and signal-to-noise ratios. Together, these findings indicate that cortical hyperexcitability in Fmr1 KO rats may act to preserve signal-to-noise ratios and signal detection threshold at the expense of sound sensitivity and fine feature discrimination, highlighting a potential mechanistic locus for a range of auditory behavioral phenotypes in FXS.

Most patients with sensorineural hearing loss (SNHL) may initially experience high‐frequency hearing loss linked to greater vulnerability of outer hair cells (OHCs) in the cochlear basal turn. However, the molecular mechanism underlying this susceptibility in the high‐frequency region remains unclear. Here, NOX2 is first identified as a differentially expressed gene related to oxidative damage in the apical and basal turns through single‐cell RNA sequencing. In mouse cochleae damaged by neomycin and noise, Nox2‐positive OHCs increase progressively from the apex to base, indicating that NOX2 expression clearly differed significantly between the apical and basal OHCs. In NOX2 knockout mice, OHC damage caused by neomycin and noise exposure is significantly reduced. Furthermore, knocking out NOX2 increases the expression of Nrf2 in the cytoplasm and Nrf2 nuclear translocation in OHCs. In addition, Nrf2 inhibitors counteract the protective effect of NOX2 knockout against neomycin. Finally, when Nox2 is used as the target, ginsenoside Rg1 is identified as a compound with protective effects against neomycin‐induced hearing loss. In summary, these results indicate NOX2 is highly correlated with high‐frequency OHCs vulnerability in the cochlea and is a potential intervention target for the clinical treatment of SNHL.

Hearing loss is a pervasive global health challenge with profound impacts on communication, cognitive function, and quality of life. Recent studies have established age-related hearing loss as a significant risk factor for dementia, highlighting the importance of hearing loss research. Auditory brainstem responses (ABRs), which are electrophysiological recordings of synchronized neural activity from the auditory nerve and brainstem, serve as in vivo readouts for sensory hair cell, synaptic integrity, hearing sensitivity, and other key features of auditory pathway functionality, making them highly valuable for both basic neuroscience research and clinical diagnostics. Despite their utility, traditional ABR analyses rely heavily on subjective manual interpretation, leading to considerable variability and limiting reproducibility across studies. Here, we introduce Auditory Brainstem Response Analyzer (ABRA), a novel open-source graphical user interface powered by deep learning, which automates and standardizes ABR waveform analysis. ABRA employs convolutional neural networks trained on diverse datasets collected from multiple experimental settings, achieving rapid and unbiased extraction of key ABR metrics, including peak amplitude, latency, and auditory threshold estimates. We demonstrate that ABRA’s deep learning models provide performance comparable to expert human annotators while dramatically reducing analysis time and enhancing reproducibility across datasets from different laboratories. By bridging hearing research, sensory neuroscience, and advanced computational techniques, ABRA facilitates broader interdisciplinary insights into auditory function. An online version of the tool is available for use at no cost at https://abra.ucsd.edu.

Negative feedback of the cochlear efferent system plays a critical role in control of hearing sensitivity and protection from noise trauma. Type II auditory nerves (ANs) innervate outer hair cells (OHCs) in the cochlea and provide an input to the cochlear efferent system to achieve hearing sensitivity controlling and protection; in particular, medial olivocochlear efferent nerves innervate OHCs to control OHC electromotility, which is an active cochlear amplifier in mammals. However, little is known about channel information underlying type II AN activity and consequent function. Here, we report that ATP-gated P2x7 receptor had a predominant expression at type II spiral ganglion (SG) neurons and the synaptic areas under inner hair cells and OHCs with lateral and medial olivocochlear efferent nerves. Knockout (KO) of P2x7 increased hearing sensitivity with enhanced acoustic startle response, auditory brainstem response, and cochlear microphonics by increasing OHC electromotility. P2x7 KO also increased susceptibility to noise and exacerbated ribbon synapse degeneration. Middle-level noise exposure could impair active cochlear mechanics resulting in hearing loss in P2x7 KO mice. These data demonstrate that P2x7 receptors have a critical role in type II SG neuron’s function and the cochlear efferent system to control hearing sensitivity; deficiency of P2x7 receptors can impair type II SG neuron’s function and the cochlear efferent suppression leading to increase of active cochlear amplification and hearing oversensitivity, i.e., hyperacusis, and susceptibility to noise, which may also associate with other hearing disorders, such as tinnitus.

Hearing loss is common in conditions caused by ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) deficiency, such as generalized arterial calcification of infancy and autosomal recessive hypophosphatemic rickets type 2. Mechanistically, it is hypothesized that poor mineralization of the auditory ossicles leads to impaired sound transmission in the middle ear. Here we investigated whether enzyme replacement therapy (ERT) improves hearing loss in an Enpp1-deficient mouse model and whether this is associated with corrected bone properties in the ossicles. For this purpose, male Enpp1asj/asj mice were subjected to either a soluble or bone-targeted ERT of ENPP1-Fc. Hearing function and bone properties of the malleus, the first bone of the ossicular chain, were evaluated and compared to untreated Enpp1asj/asj and WT mice at the age of 17 wk. In untreated Enpp1-deficient mice, we found elevated hearing thresholds at stimulus frequencies of 8, 16, and 32 kHz, suggesting a generalized impairment of hearing. The hearing deficits observed in Enpp1asj/asj mice were partially or fully corrected by both soluble and bone-targeted ERT, as evidenced by the restoration of auditory brainstem response thresholds, with dose dependence and generally stronger effect of bone-targeted ERT. This was not only associated with corrected blood plasma markers of mineral metabolism but also improved matrix mineralization and restored osteocyte properties in the malleus. In addition, for the first time in mice, we were able to demonstrate the occurrence of mineralized osteocyte lacunae in Enpp1asj/asj mice, a phenomenon that was corrected by bone-targeted but not soluble ERT, underscoring the need for targeted delivery for effective treatment. In contrast to osteocyte lacunar mineralization in humans (ie, micropetrosis), the intra-lacunar mineral was overall less mineralized than the adjacent bone. In conclusion, our results point toward the potential benefit of correcting ossicular mineralization to prevent hearing loss in ENPP1 deficiency.

Many elderly listeners have difficulties with speech-in-noise perception, even if auditory thresholds in quiet are normal. The mechanisms underlying this compromised speech perception with age are still not understood. For identifying the physiological causes of these age-related speech perception difficulties, an appropriate animal model is needed enabling the use of invasive methods. In a comparative behavioral study, we used young-adult and quiet-aged Mongolian gerbils as well as young and elderly human subjects to investigate age-related changes in the discrimination of speech sounds in background noise, evaluating whether gerbils are an appropriate animal model for the age-related decline in speech-in-noise processing of human listeners. Gerbils and human subjects had to report a deviant consonant-vowel-consonant combination (CVC) or vowel-consonant-vowel combination (VCV) in a sequence of CVC or VCV standards, respectively. The logatomes were spoken by different speakers and masked by a steady-state speech-shaped noise. Response latencies were measured to generate perceptual maps employing multidimensional scaling, visualizing the subjects’ internal representation of the sounds. By analyzing response latencies for different types of vowels and consonants, we investigated whether aging had similar effects on the discrimination of speech sounds in background noise in gerbils compared to humans. For evaluating peripheral auditory function, auditory brainstem responses and audiograms were measured in gerbils and human subjects, respectively. We found that the overall phoneme discriminability in gerbils was independent of age, whereas consonant discriminability was declined in humans with age. Response latencies were generally longer in aged than in young gerbils and humans, respectively. Response latency patterns for the discrimination of different vowel or consonant types were different between species, but both gerbils and humans made use of the same articulatory features for phoneme discrimination. The species-specific response latency patterns were mostly unaffected by age across vowel types, while there were differential aging effects on the species-specific response latency patterns of different consonant types.

Stereocilia are rod-like mechanosensory projections consisting of unidirectionally oriented actin filaments that extend into the inner ear hair cell cytoskeleton, forming dense rootlets. Taperin (TPRN) localizes to the narrowed-down base of stereocilia, where they pivot in response to sound and gravity. We show that TPRN-deficient mice have progressive deafness characterized by gradual asynchronous retraction and fusion of outer and inner hair cell stereocilia, followed by synaptic abnormalities. Stereocilia that lack TPRN develop warped rootlets with gradual loss of TRIOBP-5 and ANKRD24 from mechanosensory rows starting postnatally. In contrast, TPRN overexpression causes excessive F-actin bundling, extra rows, and over-elongation of stereocilia during development. Purified full-length mouse TPRN cross-links F-actin into bendable bundles reflecting in vivo data. This F-actin–bundling ability is attributed to the TPRN N-terminal region. TPRN interacts with the membrane receptor PTPRQ, connecting the F-actin core to the plasma membrane, stabilizing stereocilia. Thus, TPRN is a specialized F-actin bundler strategically located to augment stereocilia rootlet formation and their pivot point flexibility for sustained sound-induced deflections.

Frequency analysis by the cochlea forms a key foundation for all subsequent auditory processing. Stimulus-frequency otoacoustic emissions (SFOAEs) are a potentially powerful alternative to traditional behavioral experiments for estimating cochlear tuning without invasive testing, as is necessary in humans. Which methods accurately predict cochlear tuning remains controversial due to only a single animal study comparing SFOAE-based, behavioral, and cochlear frequency tuning in the same species. The budgerigar ( Melopsittacus undulatus ) is a parakeet species with human-like behavioral sensitivity to many sounds and the capacity to mimic speech. Intriguingly, previous studies of critical bands, psychophysical tuning curves, and critical ratios in budgerigars show that behavioral tuning sharpness increases dramatically with increasing frequency from 1 to 3.5 kHz, doubling once per octave with peak tuning sharpness from 3.5 to 4 kHz. The pattern contrasts with slower monotonic growth of behavioral tuning sharpness with increasing frequency in other animals, including most avian species, suggesting a possible auditory specialization in budgerigars. We measured SFOAE-based and cochlear-afferent tuning in budgerigars, for comparison to previously reported behavioral results. SFOAE-based and cochlear-afferent tuning sharpness both increased monotonically and relatively slowly for higher frequencies, in contrast to the behavioral pattern. SFOAE-based tuning in budgerigars accurately predicted cochlear frequency tuning, and both measures aligned with typical patterns of cochlear tuning in other species. Divergent behavioral tuning in budgerigars is unlikely attributable to the periphery and could reflect specializations for central processing of masked signals. Our findings highlight the value of SFOAEs for estimating cochlear tuning and caution against direct inference of peripheral tuning from behavioral critical bands, psychophysical tuning curves, and critical ratios.

The preservation of synaptic integrity and physiological activity is pivotal for post-traumatic auditory rehabilitation following acoustic overexposure. Neuritin, a neurotrophic factor that facilitates synapse formation, maturation, and enhanced synaptic transmission, is essential for synapse development. In this study, we established a noise-induced cochlear synaptopathy model in CBA/CaJ mice, revealing a temporal association between endogenous Neuritin expression and synaptic density. Furthermore, administration of recombinant Human Neuritin (rhNeuritin) effectively preserves synaptic density in the cochlear basal turn at 7 days and 14 days following noise exposure. Importantly, it preserves the density of functional synapses (represented by overlapping CtBP2 and GluA2 puncta) and synapse function (indicated by ABR I wave amplitudes), thus diminishing the impairment of auditory function. In addition, rhNeuritin reverses the decrease in phosphorylated extracellular signal-regulated protein kinase 1/2 (p-ERK1/2) levels resulting from noise exposure. By primarily preserving both the number and functionality of synapses in the basal turn, potentially via the induction of ERK1/2 phosphorylation, rhNeuritin mitigated hearing loss. These findings underscore the protective efficacy of rhNeuritin against noise-induced synaptic injury.

Aging is associated with deficits in auditory functioning. Characterization of auditory deficits that originate in middle-age is crucial for understanding the initial age-related functional impairments and the spatio-temporal progression of age-related auditory pathophysiology. Early age-related deficits in auditory processing are evident in difficult listening conditions, such as background noise, before becoming evident in quiet. To investigate the effect of noise on age-related auditory dysfunction, we collected suprathreshold auditory brainstem responses (ABRs) from young, middle-aged, and aged CBA/CaJ mice in quiet and broad-band background noise. We utilized multiple ABR metrics, including phase locking value (PLV), a measure of neural synchrony correlated to speech-in-noise understanding in humans. Despite no differences in auditory processing in quiet between young and middle-aged mice, middle-aged mice exhibited a distinct auditory phenotype from both young and aged mice in background noise conditions. We found that noise significantly decreased amplitude in middle-aged mice more than in young and aged mice. Noise significantly increased latencies for wave I and V in young mice, but only affected wave V in middle-aged mice and did not affect aged latencies. Noise significantly decreased PLV in middle-aged mice to a greater extent than in young mice, but to a lesser extent in aged mice. These results show that middle-aged mice have a distinct, auditory dysfunction phenotype evident in background noise. Our data show that suprathreshold auditory function in noise can identify early age-related hearing loss and can be used as a sensitive tool for detecting auditory dysfunction in normal hearing animal models.

Noise-induced hearing loss (NIHL) poses an emerging global health problem with only ear protection or sound avoidance as preventive strategies. The cochlea receives some protection from medial olivocochlear efferent neurons, providing a potential target for therapeutic enhancement. Cholinergic efferents release acetylcholine (ACh) to hyperpolarize and shunt the outer hair cells (OHCs), reducing sound-evoked activation. The (α9)2(α10)3 nicotinic ACh receptor (nAChR) on the OHCs mediates this effect. Transgenic knockin mice with a gain-of-function nAChR (α9L9'T) suffer less NIHL. α9 knockout mice are more vulnerable to NIHL but can be rescued by viral transduction of the α9L9'T subunit. In this study, an HA-tagged gain-of-function α9 isoform was expressed in wild-type mice to reduce NIHL. Synaptic integration of the virally expressed nAChR subunit was confirmed by HA immunopuncta localized to the postsynaptic membrane of OHCs. After noise exposure, AAV2.7m8-CAG-α9L9'T-HA (α9L9'T-HA)-injected mice had less hearing loss (auditory brainstem response [ABR] thresholds and threshold shifts) than did control mice. ABRs of α9L9'T-HA-injected mice also had larger wave-1 amplitudes and better recovery of wave-1 amplitudes post noise exposure. Thus, virally expressed α9L9'T combines effectively with native α9 and α10 subunits to mitigate NIHL in wild-type cochleas.

Aminoglycoside antibiotics remain indispensable despite their ototoxicity. Like other sensorineural forms, aminoglycoside-induced hearing loss (AGIHL) has no effective pharmacotherapy. Oxidative stress, apoptosis, excitotoxicity and inflammation are key pathological factors of the disease. We hypothesised that selegiline, an irreversible monoamine oxidase-B (MAO-B) inhibitor used in Parkinson’s disease, could be repurposed as an otoprotective agent against AGIHL and its effect on dopamine (DA) release from lateral olivocochlear (LOC) fibres, the efferent division of a protective feedback loop plays a major role in the protection against excitotoxicity. Selegiline mitigated AGIHL in BALB/c mice in a dose-dependent manner at different auditory brainstem response frequencies, including 16 kHz, the hearing sensitivity optimum of the animals. It also enhanced the action potential-evoked DA release from LOC efferents in mouse cochlear preparation dose-dependently. Inhibition of DA reuptake contributed to its basic effect of saving DA from metabolism. Among four selegiline analogues tested, the one that increased LOC DA release also provided otoprotection. In contrast, neither safinamide (a reversible MAO-B inhibitor) nor LJP-1207 (a selective semicarbazide-sensitive amine oxidase/vascular-adhesion protein 1 (SSAO/VAP1) inhibitor) prevented AGIHL, despite their antioxidant and anti-inflammatory properties. The reversibility or lack of MAO-B inhibition in safinamide and LJP-1207, respectively, as well as the absence of the propargylamine moiety with known intrinsic neuroprotective activity in both molecules, may explain their ineffectiveness. Selegiline, or certain propargylamine analogues of it, offer a promising therapy against AGIHL by addressing its multifactorial pathology through antioxidant, antiapoptotic, neuroprotective, and anti-inflammatory actions, while enhancing endogenous DAergic protective mechanisms.

The genus Peromyscus has been extensively used as a model for ecological, behavioral, and evolutionary studies. This study used auditory brainstem responses (ABRs), craniofacial morphology, and pinna measurements to compare two wild-caught species, Peromyscus leucopus and Peromyscus maniculatus. It was observed that P. leucopus exhibited larger features and bigger overall size compared to P. maniculatus. ABR recordings showed similar hearing thresholds with peak sensitivity between 8 and 46 kHz for both species. There were no significant differences between species for absolute amplitudes of waves IV and I, with significantly higher amplitude ratio of wave IV to wave I in P. leucopus across intensities. There were also species differences (faster wave I in P. maniculatus) and sex differences (faster wave I in female P. leucopus) for absolute latency, which were no longer significant when considering inter-peak latency between waves I and IV. Finally, faster normalized latencies of the binaural interaction component (BIC) were observed in P. maniculatus, while no differences were observed across relative BIC amplitude between species. These results provide additional ABR related data that expand the use of both Peromyscus species as future models for auditory research.

Background/Objectives: Obesity is a risk factor for several diseases; however, less has been researched about how diet-induced obesity may affect the auditory system. In this sense, the purpose of this study was to evaluate the effect of diet-induced obesity on the functionality and integrity of the outer hair cells, a key component of the organ of Corti, inside the cochlea. Furthermore, we hypothesized that adipose tissue (AT) status is associated with impaired outer hair cell auditory amplification in young C57BL/6 mice, contributing to increased vulnerability to hearing damage. Methods: Weaning male C57BL/6J mice (7 weeks old) weighing 22–23 g were divided into two diet groups: (i) a control diet or (ii) a high-fat diet (HFD) for 12 or 16 weeks. Metabolic parameters (body and AT weight, glucose tolerance test), AT dysfunction markers (AT remodeling, adipocyte size, crown-like structures), and outer hair cell function (distortion products otoacoustic emissions (DPOAEs) threshold and amplitudes) and integrity (hair cells cell count) were evaluated. Results: We observed that mice fed an HFD for 16 weeks showed a higher DPOAE threshold against stimuli at 16 KHz and a lower count of outer hair cells in the medial section of the cochlea. These results demonstrate a correlation between body and AT weight specifically at 16 weeks of treatment, the time point at which we observed a marked AT dysfunction. Conclusions: Taken together, our results suggest that obese mice with AT dysfunction have an altered auditory efferent system, characterized by a higher DPOAE threshold and a lower outer hair cell count in the medial section, which may impact signal transduction.

Cisplatin‐induced ototoxicity remains a clinical dilemma with limited mechanistic understanding and no food and drug administration (FDA)‐approved therapies. Despite emerging roles of small extracellular vesicles (sEV) in drug ototoxicity, their molecular cargo profiles and causal roles to cisplatin‐induced ototoxicity are unexplored. This study systematically investigates sEV derived from cochlear explants treated with cisplatin (Cis‐sEV) and controls (Ctrl‐sEV) using multi‐omics profiling. Through small RNA sequencing, 83 differentially expressed microRNAs (miRNAs) are identified in Cis‐sEV compared to Ctrl‐sEV. Notably, mmu‐miR‐34a‐5p, mmu‐miR‐140‐5p, mmu‐miR‐15b‐5p, mmu‐miR‐25‐3p, and mmu‐miR‐339‐5p are significantly upregulation in Cis‐sEVs. Predicted target pathways of these differentially expressed miRNAs are enriched in apoptosis, inflammation, and cellular damage, indicating their potential involvement in cisplatin‐induced cochlear damage. LC‐MS/MS analysis reveals 90 upregulated and 150 downregulated proteins in Cis‐sEV, with many involved in damage response. Specifically, CLTC, CCT2, ANXA6, and HSPA8 are uniquely upregulated proteins in Cis‐sEV, and CLTC and ANXA6 are exclusively co‐localized in hair cells (HCs) post‐cisplatin exposure, suggesting that Cis‐sEV originate primarily from damaged HCs. Moreover, CLTC in sEV may serve as a potential biomarker for cisplatin‐induced ototoxicity as verified in both in vitro and in vivo models. This study provides novel insights into the molecular mechanisms of cisplatin‐induced ototoxicity and identifies potential biomarker and therapeutic targets.