ABR/DPOAE publications

Background: Neonatal hypoxia-ischemia (HI) disrupts brain development and can impair sensory circuit maturation. However, how HI vulnerability is modified within developing auditory pathways remains poorly defined. Purpose: Metformin is used during pregnancy in select cases and modulates cellular energy signaling. Here, we tested whether maternal metformin administration during gestation alters functional and cellular outcomes in offspring brain after neonatal HI. Methods: Pregnant rat dams received metformin in drinking water, and offspring rat pups underwent HI during early postnatal life. Auditory pathway function was assessed in vivo using auditory brainstem responses (ABRs), and cellular pathology within the medial nucleus of the trapezoid body (MNTB) was evaluated by immunohistochemistry across postinjury developmental time points. Results: HI significantly elevated click-evoked ABR thresholds and reduced wave II and III amplitudes, whereas maternal metformin exposure prevented the HI-induced click-threshold elevation and preserved wave II and III amplitudes without altering peripheral or central conduction times. Histologically, HI produced an age-dependent decline in MAP2-positive neuronal density in the MNTB, culminating in marked neuronal loss at later postnatal stages. Notably, maternal metformin partially rescued HI-associated reductions in MNTB neurons, with a parallel trend toward preservation of oligodendrocyte lineage cells. Conclusion: Together, these findings indicate that maternal metformin administration during pregnancy enhances metabolic signaling and mitigates HI-related auditory brainstem dysfunction and cellular pathology in offspring, supporting maternal metabolic modulation as a determinant of neonatal sensory brain injury outcomes.

Cisplatin-induced ototoxicity leads to irreversible hearing loss in approximately 50% of treated patients, largely due to the cochlea's exceptionally poor cisplatin clearance compared with other organs. Although sodium thiosulfate (STS), a hydrophilic small molecule, is an established otoprotectant, achieving therapeutically sufficient cochlear concentrations remains challenging because systemic administration is limited by the blood-labyrinth barrier. Here, we report a viscosity-tunable microgel-in-sol system based on hyaluronic acid (HA) that enables sustained, localized delivery of STS to the inner ear via intratympanic injection. The STS-loaded microgel was readily injectable through 31 G needles and provided a six-fold extension in drug release duration compared with free STS solution. However, direct microgel injection caused significant occlusion of the middle ear cavity due to swelling and poor clearance. To overcome this limitation, we developed a microgel-in-sol formulation composed of an HA solution and microgel at a 3:1 volumetric ratio. This formulation exhibited concentration-dependent, lubricant-like viscosity while maintaining effective drug delivery and preserving auditory function, as confirmed by in vivo auditory brainstem response (ABR) measurements. Overall, this microgel-in-sol strategy represents a biocompatible, minimally invasive approach for localized inner-ear drug delivery.

CDC42 is involved in multiple signaling pathways, including actin organization and polarity. We previously reported progressive sensorineural hearing loss (SNHL) in inner ear hair cell (HC)-specific Cdc42-knockout (Atoh1-Cre+/-;Cdc42flox/flox) mice. However, the phenotype was milder than expected, suggesting possible redundancy with other Rho-family GTPases. Thereafter, Takenouchi-Kosaki syndrome (TKS), caused by de novo CDC42 mutations and manifesting as SNHL, was reported, in which the p.Y64C mutation was speculated to be constitutively active. However, the relationship between CDC42 status and hearing phenotypes in TKS remains unclear. Using cell models, mouse models, and patient data, we propose that impaired and/or dysregulated cycling between GDP/inactive and GTP/active forms, through either loss-of-function or constitutive activation, can lead to SNHL. Furthermore, to test redundancy, we generated HC-specific Cdc42;RhoQ double-knockout (Atoh1-Cre+/-;Cdc42flox/flox;RhoQflox/flox) mice, which revealed synergistic roles of CDC42 and RHOQ in cochlear HCs. Supporting this synergy, MDCK cells with CDC42 and RHOQ double knockdown showed greater phospho-cofilin, a key regulator of actin turnover, elevation than single knockdowns.

Aging has profound effects on sensory systems, such that older adults can report problems in hearing despite having normal audiometric thresholds. While it is known that older listeners have poorer temporal processing than younger listeners, there is limited understanding of how these deficits interact with effects of sound level, in particular when they are above conversational level (e.g., > 65 dB SPL). Here we wanted to investigate the link between temporal processing and sound level as a function of age in normal-hearing listeners. Using a forward-masking paradigm, auditory brainstem responses (ABRs) and behavioral detection thresholds were measured at different masker levels. It was found that with increasing age and masker sound level, older listeners’ Wave V amplitudes decreased and directly correlated with behavioral detection thresholds of the probe stimulus in the forward-masking paradigm. These results elucidate the fundamental effects of aging on temporal processing and its interactions with sound level in the central auditory system. The results of this study have clinical implications for the concept of “normal hearing” in the aging population and how older listeners may struggle in different listening environments that are not captured by simple audiometry. Further delineating the important effects of aging will pave the way for earlier clinical diagnosis of hearing disorders and personalized treatments for different forms of age-related hearing loss.

Objective Cisplatin, a life-saving chemotherapeutic drug, causes ototoxicity. Although sodium thiosulfate is used to prevent ototoxicity in pediatric patients, no other intervention has been approved for clinical use against cisplatin-induced hearing loss. Hence, there is an urgent need to identify drugs that prevent cisplatin ototoxicity. Methods CBA/J mice were treated with cisplatin (3 mg/kg, i.p., daily for 5 days), and MnTBAP (10 mg/kg, i.p., daily for 8 days) was used to inhibit cisplatin-induced ototoxicity. Auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs) were recorded before and after treatment to assess hearing loss, while immunohistochemistry with anti-Myosin-VIIa was conducted to examine hair cell loss, with phalloidin to examine spiral ganglion neuron (SGN) loss, and with anti-nitrotyrosine to assess nitrotyrosine levels. Results Cisplatin treatment elevated the nitrotyrosine levels in hair cells and SGNs and increased the loss of these cells in the middle and basal cochlear regions. A negative correlation was observed between cisplatin-induced changes in the hair cell count or SGN density and nitrotyrosine levels. Cisplatin treatment elevated the hearing thresholds, as indicated by the ABRs, and lowered the DPOAE amplitudes, suggesting cisplatin-induced hearing loss. However, MnTBAP cotreatment prevented the cisplatin-induced changes in hearing sensitivity and reversed the morphological changes. Conclusion The otoprotection observed with MnTBAP cotreatment along with the attenuation of cisplatin-induced increase in nitrotyrosine levels in the cochlea indicates its potential as an inhibitor of cochlear nitrative stress and its utility in mitigating cisplatin-induced ototoxicity.

Individuals with fetal alcohol spectrum disorders exhibit impaired auditory processing and atypical auditory behaviors across the disorder's spectrum. Although low to moderate prenatal alcohol exposure (PAE) is a prevalent type of exposure, the developmental trajectory of auditory processing deficits resulting from this level of exposure remains unknown. To examine the effects of PAE in the auditory system, we utilized the maternal voluntary alcohol consumption paradigm to model chronic low to moderate PAE throughout gestation. We measured auditory brainstem responses (ABRs) in juvenile mice (postnatal day 16–19) and longitudinally across early adolescence (4–5 weeks), late adolescence (7–8 weeks), and young adulthood (12–14 weeks). ABR abnormalities were first observed in juvenile PAE mice. The effects of PAE on brainstem auditory processing were most prominent in early adolescence, largely dissipated in late adolescence, and showed a reemergence in early adulthood. PAE mice showed elevated ABR thresholds, prolonged wave latencies, and reduced wave amplitudes. Ratios of ABR peak 3 relative to the first ABR peak indicated that the auditory brainstem pathways were hyperactive in PAE mice. The amplitude ratio was found to be elevated from early adolescence to early adulthood, suggesting that PAE has a persistent effect on auditory processing. We found a significant correlation between the amplitude ratios in early adolescent PAE mice and dam ethanol consumption, which point toward dose‐dependent brainstem gain dysregulation. Our study shows multilevel auditory alterations highlighting the vulnerability of central auditory pathways to PAE and fills an important gap in understanding auditory processing deficits in a clinically relevant exposure model.

Focused ultrasound (FUS) is a promising noninvasive neuromodulation approach, but whether it can directly activate central auditory neurons in vivo remains unresolved. We applied high-frequency FUS (20 MHz) to the central nucleus of the inferior colliculus (CNIC) in anesthetized guinea pigs while recording electrophysiological responses from the auditory pathway and cochlea. FUS evoked cortical activity through indirect cochlear activation, possibly via skull-mediated mechanical coupling, rather than direct inferior colliculus activation, with ultrasound-evoked compound action potentials predominating in the ipsilateral cochlea. More interestingly, FUS stimulation of the CNIC induced activation of neurons and glial cells in the CNIC and auditory cortex as demonstrated by c-Fos expression, suggesting that FUS stimulation activated the afferent pathway. We also show that FUS engaged the auditory efferent system, likely via medial olivocochlear neurons, producing reduced compound action potential amplitudes, enhanced cochlear microphonics, and persistent effects lasting at least two hours, consistent with long-lasting efferent plasticity. Strikingly, FUS administered before acoustic trauma almost completely prevented noise-induced hearing loss, limiting auditory brainstem response threshold shifts to <10 dB versus ∼60 dB in controls. Gentamicin abolished these physiological and protective effects, implicating medial olivocochlear activation. These findings identify FUS as a potent noninvasive strategy for engaging auditory efferent circuits and protecting against acoustic injury.

Cisplatin–induced ototoxicity is a significant clinical issue linked to ferroptosis and mitophagy dysfunction. This study investigated how mitophagy regulates ferroptosis in cisplatin–induced hearing loss using cultured primary rat cochlear marginal cells in vitro and a C57BL/6J mouse model of cisplatin–induced ototoxicity in vivo. Cisplatin suppressed the PTEN–induced putative kinase 1 (PINK1) pathway, impaired mitophagy, and triggered ferroptosis characterized by iron overload, lipid peroxidation, increased acyl–CoA synthetase long–chain family member 4 (ACSL4), and decreased glutathione peroxidase 4. Pharmacological activation of mitophagy or PINK1 overexpression alleviated ferroptosis in vitro, while deferoxamine treatment reduced cisplatin–induced hearing loss and blood–labyrinth barrier damage in vivo. Mechanistically, restoration of mitophagy was associated with increased mitochondrial targeting and reduced cytosolic accumulation of ACSL4, potentially through mitophagic clearance, thereby suppressing ferroptosis. These findings support a model in which impaired PINK1–associated mitophagy contributes to cytosolic ACSL4 accumulation and ferroptotic injury. Modulating mitophagy and ACSL4 subcellular distribution may represent a potential strategy for mitigating cisplatin–induced ototoxicity.

Cisplatin is a widely utilized chemotherapeutic agent for the treatment of malignant cancers. However, its clinical application is significantly restricted due to its severe ototoxicity. Therefore, identifying protective medications to prevent cisplatin‐induced hearing loss (CIHL) is of paramount importance. Here, we show that AC591, derived from the classical herbal formula “Huangqi Guizhi Wuwu decoction,” exhibits notable protective effects on cisplatin‐induced ototoxicity. Our findings indicate that pretreatment with AC591 mitigates cisplatin‐induced auditory dysfunction, with its mechanism of action linked to the inhibition of p53‐mediated ferroptosis. By identifying the active components of AC591 in serum and cochlear tissues following oral administration, we recognized 18β‐glycyrrhetinic acid as an effective constituent for hearing protection. Furthermore, we confirmed that 18β‐glycyrrhetinic acid exerted otoprotective effects by binding to p53 and regulating proteins associated with ferroptosis. Collectively, our findings suggest that AC591 and 18β‐glycyrrhetinic acid may serve as promising agents for preventing CIHL.

Purpose Otoacoustic emissions (OAEs) are used to assess outer hair cell (OHC) function. Clinical interpretation of OAE responses, however, is often limited to a present/absent binary since both physiological factors and measurement variability affect the measured OAE amplitude. Prior work showed elevated OAE responses in sedated compared to awake chinchillas, pointing to the potential influence of the medial olivocochlear (MOC) efferents on amplitudes, but this finding is inconsistent across species and OAE type. Here, we aimed to further investigate the effect of anesthesia on distortion-and reflection-type emissions in chinchillas using swept stimuli and more reliable calibration methods. Methods Swept distortion-product (DP) and stimulus-frequency (SF) OAEs were measured in chinchillas with and without ketamine/xylazine sedation. Stimuli were presented using in-ear forward pressure level calibrations. DPOAE and SFOAE amplitudes and estimated Q erb from SFOAE group delays were compared across the two conditions. Results We found that low-frequency DPOAE amplitudes were elevated when animals were sedated. The difference in SFOAE amplitudes was more variable across animals but appeared mildly reduced in sedated animals. Q erb estimates were slightly higher in sedated animals at some frequencies. The effect of sedation was not different across sexes. Conclusion Taken together, these findings suggest that sedation impacts OAE measurements in chinchillas. MOC modulation could account for the present findings and differences across species. For diagnostic precision, OAE responses should be considered in the context of not only intrinsic OHC function but also extrinsic physiological processes that can modulate OHCs.

Background Hearing loss primarily results from irreversible cochlear hair cell (HC) damage caused by factors such as noise, aging, genetics, and ototoxic drugs including cisplatin. Currently, there are no effective clinical otoprotective agents available. The natural compound paeonol, derived from Paeonia suffruticosa, exhibits potential anti‐inflammatory and antioxidant properties, positioning it as a promising therapeutic candidate given the central roles of oxidative stress and inflammation in hearing loss pathogenesis. Methods and Results Using mouse cochlear explant cultures, we demonstrated that paeonol protects against cisplatin‐induced HC damage in a concentration‐dependent manner and reduces the accumulation of MitoSOX, TNF‐α, and IL‐6. In vivo, paeonol administration not only prevented cisplatin‐induced HC loss and inner HC synaptic degeneration but also conferred protection against noise‐induced HC damage and hearing loss, demonstrating broad otoprotective efficacy. Mechanistically, RNA‐seq analysis revealed that paeonol exerts its protective effect partly by preventing ribosome biogenesis dysfunction, thereby ensuring normal protein synthesis in HCs. Conclusions Together, our work demonstrates the efficacy of paeonol across multiple models and reveals a potential protective mechanism, paving the way for its development as a much‐needed otoprotective drug.

The transcription factor ATOH1 is a master regulator of mechanosensory hair-cell (HC) development in the ear. Here, we report that its target gene Casz1 regulates the maturation of outer HCs (OHCs). Genetic deletion of Casz1 during (but not after) cochlear development in the mouse caused: hearing loss; disorganization of mechanosensory stereocilia bundles in OHCs; reduced F-actin density in OHC cuticular plates; progressive OHC loss; and mild morphological alterations in inner HCs. This deletion also altered gene expression, delaying downregulation of genes expressed in immature OHCs, including the actin regulator-encoding gene Coro2a, and accelerating upregulation of genes expressed in mature OHCs. Deleting Coro2a in Casz1 mutant mice restored F-actin density in cuticular plates but increased stereocilia bundle disorganization and hearing thresholds, revealing that CORO2A provides an overall beneficial effect. Our data indicate that CASZ1 regulates transcriptional and morphological maturation of OHCs, and that CASZ1 in maturing HCs is necessary for hearing.

Aging and noise over-exposure lead to complex mixtures of cochlear degradation that impair the structure and function of outer hair cells (OHCs), inner hair cells (IHCs), and the cochlear nerve. However, IHC damage and cochlear synaptopathy (CS) remain pathologies "hidden" from the audiogram. This study aimed to compare and contrast the physiological signatures of these two popular and distinct exposure paradigms using promising non-invasive assays: Envelope Following Responses (EFRs), Auditory Brainstem Response (ABRs), Wideband Middle-Ear Muscle Reflexes (WB-MEMRs), and Distortion Product Otoacoustic Emissions (DPOAEs). We utilized chinchilla models of carboplatin exposure (CA) (N = 4) and temporary threshold shift (TTS) noise-induced CS (N = 4) to compare the physiological signatures of each type of exposure. While both groups showed unchanged ABR thresholds two weeks after exposure, EFRs, ABR Wave 5/1 ratios, and MEMRs showed distinct effects of exposure. CA and TTS exposures showed differences in the pattern and degree of decreased EFR "peakiness" across different stimulus modulation types (e.g., sinusoidal vs. rectangular). Significant elevations in ABR Wave 5/1 ratios were less-pronounced in the TTS-exposed animals. Reduced WB-MEMR amplitudes and increased WB-MEMR thresholds occurred in both groups, although this effect was more pronounced for TTS. Opposite trends in DPOAE amplitudes suggest that effects on OHC integrity and auditory efferent physiology may differ between the two exposure types and their induced pathologies. Overall, these results suggest a combination of EFR "peakiness", ABR Wave 5/1 ratio, and WB-MEMR may be useful for profiling IHC dysfunction and CS as potentially distinct forms of hidden hearing loss.

Objectives. Spatial mapping of sound frequencies along the auditory pathway is refined through sound-evoked activity during early development. However, how neonatal auditory deprivation alters this organization remains unclear. This study examined frequency-specific spatial representations in the inferior colliculus (IC) using targeted low-frequency (apical) and high-frequency (basal) cochlear stimulation, enabling direct evaluation of low-frequency pathway integrity after neonatal deafness.Methods. Sixteen Sprague-Dawley rats (8 normal-hearing [NH] and 8 neonatally deafened [ND]) were studied. Neonatal deafness was induced by daily kanamycin injections from postnatal days 4 to 17. At 8–10 weeks of age, all animals underwent unilateral cochlear implantation with bipolar electrode pairs positioned in apical and basal cochlear regions to activate low- and high-frequency pathways. Multiunit responses were recorded from the contralateral IC using a multichannel linear electrode array. Spatial tuning curves (STCs) based on cumulative discriminability were used to assess thresholds, spread of excitation, and tonotopic precision. Spiral ganglion neuron (SGN) density was quantified histologically.Results. Despite 48%–67% SGN loss across cochlear turns, electrically evoked auditory brainstem response thresholds and IC thresholds were comparable between groups, indicating preserved peripheral excitability. However, ND rats exhibited significantly broader STCs (P=0.002) and reduced dorsoventral separation of apical and basal best sites (1.18± 0.67 mm vs. 1.80±0.40 mm, P=0.039), reflecting degraded central tonotopic precision. The effects were most pronounced for apical (low-frequency) stimulation, consistent with the selective vulnerability of low-frequency pathways to early auditory deprivation.Conclusion. These findings provide direct physiological evidence that early auditory experience is critical for refining frequency-organized connectivity in the auditory midbrain. The preferential degradation of apical (low-frequency) spatial tuning offers translational insights for optimizing stimulation strategies in early-onset deafness.

Background Approximately one in three adults aged 65–74 years reports hearing difficulty, including age-related hearing loss (AHL, presbycusis). The C57BL/6 mouse is widely used in preclinical AHL research because it develops AHL relatively early. Calorie restriction (CR) attenuates AHL and improves healthspan and longevity in this strain. A recently developed transgenic C57BL/6 mouse expressing naked mole-rat hyaluronan synthase 2 ( nmrHas2 ), which produces very high molecular mass hyaluronan (vHMM-HA), also exhibits improved healthspan, reduced inflammaging, and increased longevity. Therefore, we evaluated nmrHas2 mice for evidence of alleviated AHL. Objective To determine whether AHL is attenuated in nmrHas2 mice . Methods This study supplemented a larger investigation of nmrHas2 and female reproductive aging. Tamoxifen administered at 1 month induced ubiquitous nmrHas2 expression in nmrHas2+ females; nmrHas2− controls received tamoxifen or vehicle. Auditory brainstem response (ABR) testing was performed approximately 2 weeks before mice reached 3 or 12 months of age. Cochleae and reproductive tissues were collected following euthanasia approximately 2 weeks later. Results ABR thresholds to clicks and six tones (4–32 kHz) showed marked hearing loss from 3 to 12 months of age in both nmrHas2+ mice and controls, with no evidence that nmrHas2 attenuated AHL. Cochlear nmrHas2 expression in nmrHas2+ mice was confirmed by quantitative RT-PCR. Conclusion Ubiquitous nmrHas2 expression did not attenuate AHL in C57BL/6 mice despite previously reported benefits for other aging phenotypes. These findings contrast with CR, suggesting that vHMM-HA and CR influence aging through distinct mechanisms.

Noise-induced hearing loss (NIHL) is a major public health problem caused by damage to cochlear hair cells, synapses, and spiral ganglion neurons (SGNs). Since effective treatments are lacking, we investigated cellular stress responses induced by moderate and loud noise in a mouse model of cochlear synaptopathy. RNA sequencing and spatial transcriptomics revealed that noise exposure elicited a robust but transient upregulation of endoplasmic reticulum chaperones and proteasome subunits in SGNs and their supporting cells. To target this response, we administered TRC051384, a small-molecule activator of the heat shock transcription factor Hsf1, prior to noise exposure. TRC051384 crossed the blood–labyrinth barrier and reached the cochlea, induced heat shock protein gene expression, and restored ubiquitin–proteasome function in SGNs. Notably, TRC051384 treatment enhanced auditory brainstem response threshold recovery, preserved Wave I amplitudes, and maintained ribbon synapse density. Together with the existing literature, these findings identify proteotoxic stress in spiral ganglion neurons as a contributor to noise-induced hearing loss and support pharmacological activation of HSF1 as a promising therapeutic strategy.

Difficulties understanding speech in noise remain a common complaint even among listeners with normal hearing sensitivity, highlighting the need for objective, more effective measures of real-world listening. The goal of this study was to validate the use of a novel, chirped-speech (Cheech) stimulus—continuous, naturally-spoken speech fused with chirps designed to elicit robust auditory evoked potentials—to characterize relationships between speech recognition, listening effort, and auditory neural encoding. Twenty-five normal-hearing adults completed a sentence-recognition task using both original (unmodified) and Cheech-modified AzBio sentence lists in quiet, +3 dB, and −3 dB signal-to-noise ratio (SNR) conditions while neural responses from the brainstem through cortex were recorded simultaneously. Speech recognition remained near ceiling in quiet but declined with decreasing SNR for both original and Cheech stimuli. Compared with clean speech, Cheech-modified speech showed slightly poorer recognition performance as SNR decreased and somewhat higher perceived effort overall. Yet, Cheech was highly effective at evoking auditory responses from the brainstem (auditory brainstem response, ABR) through the cortex (including middle- and late-latency responses, MLR and LLR) even with <5 minutes listening time per condition. Neural responses showed reduced amplitudes and prolonged latencies as SNR decreased. In general, ABR latencies and wave I amplitudes were associated with speech-in-noise recognition performance, whereas cortical responses (MLR Na, Nb, and LLR P1) were associated with subjective workload. These findings show that Cheech-modified speech preserves intelligibility while yielding robust, multilevel neural recordings during sentence perception, offering a promising approach to examine hierarchical auditory processing under ecologically relevant speech-in-noise conditions.

Mammalian cochlear hair cells convert acoustic stimuli into electrical signals, which are relayed to the central auditory pathway via auditory neurons. Progressive loss of hair cells and their synapses is a characteristic of age‐related hearing loss (ARHL), but the underlying mechanisms remain poorly understood. In this study, we tested the hypothesis that hair cell physiological properties change with age in CBA/CaJ mice, a strain known for its slow ARHL progression. We found that hair cell size began to decrease from 10 months of age, well before detectable increase in hearing thresholds from auditory brainstem responses. This structural change was associated with a significant decrease in the size of the basolateral membrane current, in particular that carried by the large conductance calcium‐activated potassium (BK) channel currents ( I K,f ) in the apical inner hair cells (IHCs). However, the size of the mechanoelectrical transducer (MET) current measured in the IHCs remained unaffected at least up to 22 months of age. Our results provide clear evidence of an early change in the physiological properties of apical IHCs with age, which precedes measurable hearing loss, suggesting that these cellular deficits might define a distinct pathological route in the CBA/CaJ mice.

Introduction The mitochondrial calcium uniporter (MCU) mediates mitochondrial Ca 2⁺ uptake, but its involvement in cisplatin-induced ototoxicity remains poorly understood. We investigated MCU expression and its association with cisplatin-induced injury in mouse cochlear basilar membranes and HEI-OC1 cells. Methods MCU protein abundance and localization were assessed by Western blotting and immunofluorescence. MCU expression was genetically reduced by lentiviral knockdown, and Ru360 was used as a pharmacological intervention. Apoptosis-related proteins and transcriptomic changes were evaluated. An acute cisplatin-induced ototoxicity model was established in C57BL/6 mice and assessed using auditory brainstem response (ABR) measurements and outer hair cell counts. Results Cisplatin increased MCU expression and reduced SERCA2 expression; the cisplatin-induced increase in MCU was partially reversed by BAPTA-AM and the endoplasmic reticulum stress inhibitor 4-PBA. MCU knockdown did not affect basal cell viability but attenuated cisplatin-induced reductions in viability, TUNEL positivity, and cleaved caspase-3. It was also associated with increased SERCA2 and decreased IP3R, GRP75, and VDAC1 expression. RNA sequencing identified differentially expressed genes enriched in autophagy-related processes and mTOR signaling. MCU knockdown was associated with increased PI3K/AKT/mTOR signaling and changes in Beclin1, LC3B-II, and p62. Ru360 cotreatment partially reproduced the protective phenotype in vitro and was associated with attenuated ABR threshold elevation at selected frequencies and reduced outer hair cell loss in vivo . Discussion These findings support an association between MCU-related signaling, PI3K/AKT/mTOR pathway activation, altered autophagy-related markers, and reduced cisplatin-induced cochlear injury.

Understanding the molecular basis of hair cell function is essential for elucidating inner ear physiology and developing therapies for auditory–vestibular disorders. Here, we identify acyl-CoA binding domain-containing 7 ( Acbd7 ) as a hair cell-specific gene critical for sensory maintenance. Single-cell transcriptomics of mouse cochlear organoids revealed Acbd7 as a top hair cell-enriched transcript, with its spatiotemporal expression confirmed from embryonic development through adulthood in both auditory and vestibular hair cells. Acbd7 ‑deficient mice exhibited pronounced hair cell degeneration, characterized by synaptic defects and diminished calcium currents in inner hair cells and loss of outer hair cells. Transcriptomic and proteomic analyses linked Acbd7 to the regulation of Ca 2+ signaling and fatty acid metabolism pathways. Our findings establish Acbd7 as a critical regulator of Ca 2+ homeostasis and functional integrity in hair cells, thereby elucidating a key mechanism by which a fatty acid metabolism factor sustains hair cell function and providing potential therapeutic targets for inner ear disorders.