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Cisplatin is a commonly used chemotherapy agent with a nearly universal side effect of sensorineural hearing loss. The cellular mechanisms underlying cisplatin ototoxicity are poorly understood. Efforts in drug development to prevent or reverse cisplatin ototoxicity have largely focused on pathways of oxidative stress and apoptosis. An effective treatment for cisplatin ototoxicity, sodium thiosulfate (STS), while beneficial when used in standard risk hepatoblastoma, is associated with reduced survival in disseminated pediatric malignancy, highlighting the need for more specific drugs without potential tumor protective effects. The unfolded protein response (UPR) and endoplasmic reticulum (ER) stress pathways have been shown to be involved in the pathogenesis of noise-induced hearing loss and cochlear synaptopathy in vivo, and these pathways have been implicated broadly in cisplatin cytotoxicity. This study sought to determine whether the UPR can be targeted to prevent cisplatin ototoxicity. Neonatal cochlear cultures and HEK cells were exposed to cisplatin, and UPR marker gene expression and cell death measured. Treatment with ISRIB (Integrated Stress Response InhIBitor), a drug that activates eif2B and downregulates the pro-apoptotic PERK/CHOP pathway of the UPR, was tested for its ability to reduce apoptosis in HEK cells, hair-cell death in cochlear cultures, and hearing loss using an in vivo mouse model of cisplatin ototoxicity. Finally, to evaluate whether ISRIB might interfere with cisplatin chemoeffectiveness, we tested it in head and neck squamous cell carcinoma (HNSCC) cell-based assays of cisplatin cytotoxicity. Cisplatin exhibited a biphasic, non-linear dose-response of cell death and apoptosis that correlated with different patterns of UPR marker gene expression in HEK cells and cochlear cultures. ISRIB treatment protected against cisplatin-induced hearing loss and hair-cell death, but did not impact cisplatins cytotoxic effects on HNSCC cell viability, unlike STS. These findings demonstrate that targeting the pro-apoptotic PERK/CHOP pathway with ISRIB can mitigate cisplatin ototoxicity without reducing anti-cancer cell effects, suggesting that this may be a viable strategy for drug development.

Our sense of hearing is mediated by cochlear hair cells, of which there are two types organized in one row of inner hair cells and three rows of outer hair cells. Each cochlea contains 5-15 thousand terminally differentiated hair cells, and their survival is essential for hearing as they do not regenerate after insult. It is often desirable in hearing research to quantify the number of hair cells within cochlear samples, in both pathological conditions, and in response to treatment. Machine learning can be used to automate the quantification process but requires a vast and diverse dataset for effective training. In this study, we present a large collection of annotated cochlear hair-cell datasets, labeled with commonly used hair-cell markers and imaged using various fluorescence microscopy techniques. The collection includes samples from mouse, rat, guinea pig, pig, primate, and human cochlear tissue, from normal conditions and following in-vivo and in-vitro ototoxic drug application. The dataset includes over 107,000 hair cells which have been identified and annotated as either inner or outer hair cells. This dataset is the result of a collaborative effort from multiple laboratories and has been carefully curated to represent a variety of imaging techniques. With suggested usage parameters and a well-described annotation procedure, this collection can facilitate the development of generalizable cochlear hair-cell detection models or serve as a starting point for fine-tuning models for other analysis tasks. By providing this dataset, we aim to give other hearing research groups the opportunity to develop their own tools with which to analyze cochlear imaging data more fully, accurately, and with greater ease.

The inner ear is the hub where hair cells (HCs) transduce sound, gravity, and head acceleration stimuli to the brain. Hearing and balance rely on mechanosensation, the fastest sensory signals transmitted to the brain. The mechanoelectrical transducer (MET) channel is the entryway for the sound-balance-brain interface, but the channel-complex composition is not entirely known. Here, we report that the mouse utilizes Piezo1 (Pz1) and Piezo2 (Pz2) isoforms as MET-complex components. The Pz channels, expressed in HC stereocilia, and cell lines are co-localized and co-assembled with MET complex partners. Mice expressing non-functional Pz1 and Pz2 at the ROSA26 locus have impaired auditory and vestibular traits that can only be explained if the Pzs are integral to the MET complex. We suggest that Pz subunits constitute part of the MET complex and that interactions with other MET complex components yield functional MET units to generate HC MET currents.

AbstractBackgroundsObjectivesMaterial and MethodsResultsConclusions and SignificanceDue to the therapeutic needs of inner ear diseases, a simple method of inner ear drug delivery has been under exploration. Postauricular administration, which involves injecting the drug through the middle of the retroauricular groove, is a potential novel approach, but its mechanisms remain unclear.To investigate threshold shifts in the auditory brainstem response (ABR), as well as the morphology and quantity of hair cells on the bilateral inner ear of guinea pigs after postauricular neomycin administration.Thirty healthy guinea pigs were divided randomly into two groups and administered either neomycin 200 mg/kg or saline 1 ml via daily postauricular injection for 10 days. Auditory threshold-shifts were examined by tests of the ABR. The quantity and morphology of hair cells in the organ of Corti were assessed by confocal laser scanning microscopy.The ABR results showed that at a frequency of 16 kHz, the threshold shift was 21.00 ± 14.49 dB in the neomycin injection side, 10.00 ± 16.67 dB in the contralateral side, and 0.50 ± 3.69 dB in the saline group. At a frequency of 24 kHz, the threshold shift was 37.00 ± 16.36 dB in the neomycin injection side, 14.50 ± 9.26 dB in the contralateral side, and 1.00 ± 2.11 dB in the saline group. Histopathological analysis revealed that the outer hair cells (OHCs) in the neomycin injection side suffered significant morphological and numerical loss, while the OHC loss in the contralateral ear was less severe than in the injection side but greater than in the saline group.This study confirms that postauricular administration is a novel method of local drug delivery to the inner ear, which has practical value in future experimental modeling and the treatment of inner ear diseases. [ABSTRACT FROM AUTHOR]

BackgroundMethodsResultsConclusion\nPlain Language SummaryIn this review article, we aimed to discuss the pathogenesis of sensorineural hearing loss (SNHL) in patients with different forms of chronic rhinosinusitis (CRS), with special reference to the connection of the immune response of the nasal and middle ear mucosa and inner ear structures.Articles for this review were identified using PubMed and Google© Scholar databases.Different phenotypes of CRS may be associated with impaired function of the inner and outer cells of the organ of Corti. This is primarily due to the secondary CRS, which occurs within systemic diseases, such as granulomatosis with polyangiitis (GPA) and eosinophilic granulomatosis with polyangiitis (EGPA). Also, the tetrad, which includes CRS with nasal polyps, non-allergic asthma, hypersensitivity to nonsteroidal anti-inflammatory drugs (NSAIDs), and so-called eosinophilic otitis media can lead to SNHL.Previous studies suggest that disrupted harmony between the immune response in the nasal and middle ear mucosa and inner ear structures may contribute to developing SNHL in CRS patients. This especially applies to CRS as part of NSAID-exacerbated respiratory disease and systemic necrotizing vasculitis, including GPA and EGPA. However, the exact mechanisms of development of SNHL in different forms of CRS have not been sufficiently investigated and new studies are necessary soon. Apart from the pathophysiological basis of SNHL, different therapeutic approaches in the clinical phenotypes of CRS have also been discussed.What is known about this topic?It is known that acute rhinosinusitis, both viral and bacterial, can be associated with hearing and balance disorders.Viral microorganisms can reach the structures of the inner ear through the bloodstream and directly damage the cells of the organ Corti or cause an immune response that leads to the deposition of small immune complexes in the labyrinthine artery, thus hindering the vascularization of the receptor structures of the inner ear.Toxic substances of viral and bacterial origin, as well as mediators of inflammation, can diffuse through the oval and, especially round window of the middle ear to the inner ear structures (perilymph, endolymph, membranous labyrinth) and damage the receptor cells of the sense of hearing and balance.Available evidence suggests a high prevalence of otologic symptoms in patients suffering from chronic rhinosinusitis (CRS), affecting up to 87% of patients.The association of CRS and sensorineural hearing loss (SNHL) is one of the least researched areas in otorhinolaryngology.What does this study add?Different phenotypes of CRS may be associated with impaired function of the inner and outer cells of the organ of Corti.Disrupted harmony between the immune response in the nasal and middle ear mucosa and inner ear structures may contribute to developing SNHL in CRS patients.This applies to CRS as part of aspirin-exacerbated respiratory disease (AERD) and systemic necrotizing vasculitis, including granulomatosis with polyangiitis (GPA) and eosinophilic granulomatosis with polyangiitis (EGPA).However, the exact mechanisms of development of SNHL in different forms of CRS have not been sufficiently investigated and new studies are necessary soon. [ABSTRACT FROM AUTHOR]

ABSTRACT Microphthalmia, anophthalmia and coloboma (MAC) comprise a highly heterogeneous spectrum of congenital ocular malformations with an estimated incidence of 1 in 5000 to 1 in 30 000 live births. Although there is likely to be a genetic component in the majority of cases, many remain without a molecular diagnosis. Netrin‐1 was previously identified as a mediator of optic fissure closure from transcriptome analyses of chick and zebrafish and was shown to cause ocular coloboma when knocked out in both mouse and zebrafish. Here, we report the first patient with chorioretinal coloboma and microphthalmia harbouring a novel heterozygous likely pathogenic NTN1 missense variant, c.1483T>A p.(Tyr495Asn), validating a conserved gene function in ocular development. In addition, the patient displayed bilateral sensorineural hearing loss which was investigated by examining the sensory hair cells of ntn1a morphant zebrafish, suggesting a role for netrin‐1 in hair cell development. [ABSTRACT FROM AUTHOR]

Introduction: The vestibular nerve is comprised of neuron sub-groups with diverse functions related to their intrinsic biophysical properties. This diversity is partly due to differences in the types and numbers of low-voltage-gated potassium channels found in the neurons' membranes. Expression for some low-voltage gated ion channels like KCNQ4 is upregulated during early post-natal development; suggesting that ion channel composition and neuronal diversity may be shaped by hair cell activity. This idea is consistent with recent work showing that glutamatergic input from hair cells is necessary for the normal diversification auditory neurons. Methods: To test if biophysical diversity is similarly dependent on glutamatergic input in vestibular neurons, we examined vestibular function and the maturation of the vestibular epithelium and ganglion neurons by immunohistochemistry and patch-clamp electrophysiology in Vglut3-ko mice whose hair cell synapses lack glutamate. Results: The knockout mice showed no obvious balance deficits and crossed challenging balance beams with little difficulty. Immunolabeling of the Vglut3-ko vestibular epithelia showed normal development as indicated by an identifiable striolar zone with calyceal terminals labeled by molecular marker calretinin, and normal expression of KCNQ4 by the end of the second post-natal week. We found similar numbers of Type I and Type II hair cells in the knockout and wild-type animals, regardless of epithelial zone. Thus, the presumably quiescent Type II hair cells are not cleared from the epithelium. Patch-clamp recordings showed that biophysical diversity of vestibular ganglion neurons in the Vglut3-ko mice is comparable to that found in wild-type controls, with a similar range firing patterns at both immature and juvenile ages. However, our results suggest a subtle biophysical alteration to the largest ganglion cells (putative somata of central zone afferents); those in the knockout had smaller net conductance and were more excitable than those in the wild type. Discussion: Thus, unlike in the auditory nerve, glutamatergic signaling is unnecessary for producing biophysical diversity in vestibular ganglion neurons. And yet, because the input signals from vestibular hair cells are complex and not solely reliant on quantal release of glutamate, whether diversity of vestibular ganglion neurons is simply hardwired or regulated by a more complex set of input signals remains to be determined. [ABSTRACT FROM AUTHOR]

Introduction: Mammalian hearing depends on the dual mechanosensory and motor functions of cochlear hair cells. Both these functions may be regulated by Ca2+ release from intracellular stores. However, it is still unclear how exactly intracellular Ca2+ release may affect either hair cell mechano-electrical transduction (MET) or prestin-dependent electromotility in outer hair cells (OHCs). Methods: Here, we used photo-activatable (caged) compounds to generate fast increases of either Ca2+ or inositol-3-phosphate (IP3) in the cytosol of young postnatal rodent auditory hair cells, thereby stimulating either Ca2+- or IP3- induced releases of Ca2+ from intracellular stores. Fast Ca2+ imaging was used to monitor propagation of Ca2+ signals along the length of a hair cell. To access potential physiological role(s) of intracellular Ca2+ releases, we used whole cell patch clamp to record: i) OHC voltage-dependent capacitance, a known electrical correlate of prestin-based electromotility, and ii) MET currents evoked by stereocilia bundle deflections with fluid-jet. In the latter experiments, changes of mechanical stiffness of the hair bundles were also quantified from video recordings of stereocilia movements. Results: Ca2+ uncaging at the OHC apex initiated Ca2+ wave propagating to the base of the cell with subsequent Ca2+ build-up there. Ca2+ uncaging at the OHC base generated long-lasting and apparently self-sustained Ca2+ responses, further confirming Ca2+-induced Ca2+ release in the OHC basal region. Photoactivated IP3 initiated a slow increase of cytosolic Ca2+ ([Ca2+] i ) throughout the whole OHC, confirming the presence of slow-activated IP3-gated Ca2+ stores in OHCs. Interestingly, Ca2+ uncaging produced no effects on OHC voltage-dependent capacitance. In an OHC, the rise of [Ca2+] i is known to decrease axial stiffness of the cell and may modulate the stiffness of mechanosensory stereocilia bundles. To separate these two phenomena, we explored the potential effects of intracellular Ca2+ release on mechanical properties of stereocilia bundles in cochlear inner hair cells (IHCs). Ca2+ uncaging at the apex of an IHC caused a long-lasting increase in mechanical stiffness of stereocilia bundle without any changes in the amplitude or deflection sensitivity of the MET current. Discussion: We concluded that the most likely physiological role of IP3-gated Ca2+ release at the apex of the cell is the regulation of hair bundle stiffness. In contrast, Ca2+-induced Ca2+ release at the base of OHCs seems to regulate axial stiffness of the cells and its hyperpolarization in response to efferent stimuli, without direct effects on the OHC prestin-based membrane motors. [ABSTRACT FROM AUTHOR]

The class C orphan G-protein-coupled receptor (GPCR) GPR156, which lacks the large extracellular region, plays a pivotal role in auditory function through Gi2/3. Here, we firstly demonstrate that GPR156 with high constitutive activity is essential for maintaining auditory function, and further reveal the structural basis of the sustained role of GPR156. We present the cryo-EM structures of human apo GPR156 and the GPR156–Gi3 complex, unveiling a small extracellular region formed by extracellular loop 2 (ECL2) and the N-terminus. The GPR156 dimer in both apo state and Gi3 protein-coupled state adopt a transmembrane (TM)5/6-TM5/6 interface, indicating the high constitutive activity of GPR156 in the apo state. Furthermore, C-terminus in G-bound subunit of GPR156 plays a dual role in promoting G protein binding within G-bound subunit while preventing the G-free subunit from binding to additional G protein. Together, these results explain how GPR156 constitutive activity is maintained through dimerization and provide a mechanistic insight into the sustained role of GPR156 in maintaining auditory function. GPR156 has been identified as a regulator in auditory hair cells. Here, authors present the cryo-EM structures of human apo GPR156 and the GPR156–Gi3 complex to reveal the activation mechanism of GPR156 in maintaining auditory function. [ABSTRACT FROM AUTHOR]

In amniotes, head motions and tilt are detected by two types of vestibular hair cells (HCs) with strikingly different morphology and physiology. Mature type I HCs express a large and very unusual potassium conductance, gK, L, which activates negative to resting potential, confers very negative resting potentials and low input resistances, and enhances an unusual non-quantal transmission from type I cells onto their calyceal afferent terminals. Following clues pointing to KV1.8 (Kcna10) in the Shaker K channel family as a candidate gK, L subunit, we compared whole-cell voltage-dependent currents from utricular HCs of KV1.8-null mice and littermate controls. We found that KV1.8 is necessary not just for gK, L but also for fast-inactivating and delayed rectifier currents in type II HCs, which activate positive to resting potential. The distinct properties of the three KV1.8-dependent conductances may reflect different mixing with other KV subunits that are reported to be differentially expressed in type I and II HCs. In KV1.8-null HCs of both types, residual outwardly rectifying conductances include KV7 (Knq) channels. Current clamp records show that in both HC types, KV1.8-dependent conductances increase the speed and damping of voltage responses. Features that speed up vestibular receptor potentials and non-quantal afferent transmission may have helped stabilize locomotion as tetrapods moved from water to land. [ABSTRACT FROM AUTHOR]

Epidermal stem cells control homeostasis and regeneration of skin and hair. In the hair follicle (HF) bulge of mammals, populations of slow-cycling stem cells regenerate the HF during cyclical rounds of anagen (growth), catagen (regression), and telogen (quiescence). Multipotent epidermal cells are also present in the HF above the bulge area, contributing to the formation and maintenance of sebaceous gland and upper and middle portions of the HF. Here, we report that the transcription factor KROX20 is enriched in an epidermal stem cell population located in the upper/middle HF. Expression analyses and lineage tracing using inducible Krox20-CreERT showed that Krox20-lineage cells migrate out of this HF region and contribute to the formation of the bulge in the HF, serving as ancestors of bulge stem cells. In vivo depletion of these cells arrests HF morphogenesis. This study identifies a marker for an epidermal stem cell population that is indispensable for hair homeostasis. [ABSTRACT FROM AUTHOR]

Copyright of HNO is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of HNO is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Human inner ear organoids are three-dimensional tissular structures grown in vitro that recapitulate some aspects of the fetal inner ear and allow the differentiation of inner ear cell types. These organoids offer a system in which to study human inner ear development, mutations causing hearing loss and vertigo, and new therapeutic drugs. However, the extent to which such organoids mimic in vivo human inner ear development and cellular composition remains unclear. Several recent studies have performed single-cell transcriptomics on human inner ear organoids to interrogate cellular heterogeneity, reveal the developmental trajectories of sensory lineages and compare organoidderived vesicles to the developing human inner ear. Here, we discuss the new insights provided by these analyses that help to define new paths of investigation to understand inner ear development. [ABSTRACT FROM AUTHOR]

Age‐related hearing loss (AHL) is the most common sensory disorder amongst the older population. Inflammaging is a ≈chronic low‐grade inflammation that worsens with age and is an early sign of AHL; however, the underlying mechanisms remain unclear. We used electrophysiological and genetic approaches to establish the importance of interleukin 6 (IL‐6)‐dependent inflammation in AHL. Elevated IL‐6 in the cochlea enhanced Cav1.3 calcium channel function in the inner hair cell (IHC) synapse in mice with AHL. IL‐6 upregulated the Cav1.3 channel via the Janus kinase‐mitogen activated kinase pathway, causing neurotransmitter excitotoxicity and synapse impairment; IL‐6 deficiency or the administration of a Cav1.3 channel blocker attenuated this age‐related damage, and rescued hearing loss. Thus, IL‐6‐dependent inflammaging upregulated the Cav1.3 channel in IHCs, contributing to AHL. Our findings could help the comprehensive understanding of inflammaging's effects on AHL, aiding in early intervention to protect against hearing decline. [ABSTRACT FROM AUTHOR]

Cisplatin is widely employed in clinical oncology as an anticancer chemotherapy drug in clinical practice and is known for its severe ototoxic side effects. Prior research indicates that the accumulation of reactive oxygen species (ROS) plays a pivotal role in cisplatin's inner ear toxicity. Hesperidin is a flavanone glycoside extracted from citrus fruits that has anti-inflammatory and antioxidant effects. Nonetheless, the specific pharmacological actions of hesperidin in alleviating cisplatin-induced ototoxicity remain elusive. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) is a critical mediator of the cellular oxidative stress response, is influenced by hesperidin. Activation of Nrf2 was shown to have a protective effect against cisplatin-induced ototoxicity. The potential of hesperidin to stimulate Nrf2 in attenuating cisplatin's adverse effects on the inner ear warrants further investigation. This study employs both in vivo and in vitro models of cisplatin ototoxicity to explore this possibility. Our results reveal that hesperidin mitigates cisplatin-induced ototoxicity by activating the Nrf2/NQO1 pathway in sensory hair cells, thereby reducing ROS accumulation, preventing hair cell apoptosis, and alleviating hearing loss. [ABSTRACT FROM AUTHOR]

Objectives: Gentamicin is one of the most common ototoxic drugs that can lower patients' quality of life. Oxidative stress is a key factors inducing sensory hair cell death during gentamicin administration. So far, there are no effective drugs to prevent or treat gentamicin- induced hearing loss. A recent study found cystic fibrosis transmembrane conductance regulator (CFTR) as a new target to modulate cellular oxidative balance. The objective of this study was to estimate the effect of the CFTR activator ivacaftor on gentamicin-induced ototoxicity and determine its mechanism. Methods: The hair cell count was analyzed by Myosin 7a staining. Apoptosis was analyzed by TUNEL Apoptosis Kit. Cellular reactive oxygen species (ROS) level was detected by DCFH-DA probes. The Nrf2 related proteins expression levels were analyzed by western blot. Results: An in vitro cochlear explant model showed that gentamicin caused ROS accumulation in sensory hair cells and induced apoptosis, and this effect was alleviated by pretreatment with ivacaftor. Western blotting showed that ivacaftor administration markedly increased the protein expression of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO1), and NAD(P)H:quinone oxidoreductase 1 (NQO1). The protective effect of ivacaftor was abolished by the Nrf2 inhibitor ML385. Discussion: Our results indicate the protective role of the CFTR-Nrf2-HO1/NQO1 pathway in gentamicin-induced ototoxicity. Ivacaftor may be repositioned or repurposed towards aminoglycosides-induced hearing loss. [ABSTRACT FROM AUTHOR]

Hidden hearing loss (HHL) is characterized by normal audiometric thresholds but impaired auditory function, particularly in noisy environments. In vivo, we employed auditory brainstem response (ABR) testing and ribbon synapses counting to assess changes in mouse hearing function, and observed the morphology of hair cells through scanning electron microscopy. SRT1720 was administered to the cochlea via round window injection. In vitro, western blot analysis and RT‐qPCR were used, and Lenti‐shNrf2 was used to knockdown Nrf2 expression. In addition, various oxidative stress indicators were detected by immunofluorescence, kit‐based assays, and flow cytometry. ABR measurement of HHL mouse showed a significant increase in hearing threshold, as well as a decrease and delay in the I wave amplitude and latency on the first day after noise exposure. Histological observation showed a significant loss of ribbon synapses and stereocilia lodging. HHL mice exhibited oxidative stress, which was reduced by pretreatment with SRT1720. Additionally, SRT1720 could reduce hydrogen peroxide‐induced oxidative stress in HEI‐OC1 cells through activating the SIRT1/Nrf2 pathway. Subsequent experiments with Nrf2 knockdown confirmed the importance of this pathway. findings highlight oxidative stress as the primary contributor to HHL, with the SIRT1/Nrf2 signaling pathway emerging as a promising therapeutic target for alleviating HHL. [ABSTRACT FROM AUTHOR]

Hearing loss is a prevalent disability worldwide. Dexamethasone (Dex) is commonly used to treat hearing loss, administered either systemically or locally. However, targeted delivery of Dex to the inner ear remains challenging, which limits its therapeutic efficacy. This study aimed to develop new methods to improve Dex delivery to the inner ear and enhance its treatment effect. Mastoid, intraperitoneal, and intratympanic delivery routes for Dex were investigated in guinea pig cochlea. Liquid chromatography-mass spectrometry and immunohistochemistry were employed to compare the distribution of Dex in the perilymph and tissue uptake. Poly (lactic- co -glycolic acid) nanoparticles loaded with Dex (PLGA-NPs-Dex) were prepared, and their transport mechanism across the round window membrane (RWM) was explored. Among the three delivery routes, mastoid administration produced the highest Dex concentration in the perilymph. Compared to the control, PLGA-NPs-Dex provided significantly enhanced protection against lipopolysaccharide- and noise-induced hearing damage following mastoid administration. Mastoid delivery provides an accessible route for drug delivery to the inner ear and nanoparticle-based systems via this route represent a viable strategy for treating inner ear diseases. This approach caused less damage to the inner ear, making it a promising option for clinical use in treating hearing loss. Mastoid approach was a novel method for local drug delivery into the inner ear. PLGA-NPs-Dex showed a significantly better hearing-protective effect against lipopolysaccharides- and noise-induced damages following mastoid delivery. [Display omitted] • Mastoid approach was a novel method for local drug delivery into the inner ear. • Mastoid administration yielded the higher concentration of Dex in the perilymph than the traditional delivery routes. • PLGA-NPs-Dex was prepared and the transport mechanism of it across the round window membrane was studied • PLGA-NPs-Dex showed a better hearing-protective effect against LPS- and noise-induced damages following mastoid delivery. [ABSTRACT FROM AUTHOR]

Summary: The root epidermis of tracheophytes consists of hair‐forming cells (HCs) and nonhair cells (NCs). The HC distribution pattern is classified into three types: random (Type I), vertically alternating (Type II), and radial (Type III). Type III is found only in core eudicots and is known to be position‐dependent in superrosids with HCs positioned between two underlying cortical cells. However, the evolution of Type III and the universality of its position dependency in eudicots remain unclear.We surveyed the HC distribution in basal and Type III‐exhibiting core eudicots and conducted genomic analyses to get insight into whether eudicots share the same genetic network to establish Type III.Our survey revealed no canonical Type III in basal eudicots but a reverse Type III, with NCs between two cortical cells and HCs on a single cortical cell, in Papaveraceae of basal eudicots. Type III‐exhibiting species from both superrosids and superasterids showed the canonical position dependency of HCs. However, some key components for Type III determination were absent in the genomes of Papaveraceae and Type III‐exhibiting superasterids.Our findings identify a novel position‐dependent type of HC patterning, reverse Type III, and suggest that Type III emerged independently or diversified during eudicot evolution. [ABSTRACT FROM AUTHOR]

The mechanosensory hair cell of the vertebrate inner ear responds to the mechanical deflections that result from hearing or change in the acceleration due to gravity, to allow us to perceive and interpret sounds, maintain balance and spatial orientation. In mammals, ototoxic compounds, disease, and acoustic trauma can result in damage and extrusion of hair cells, without replacement, resulting in hearing loss. In contrast, non-mammalian vertebrates can regenerate sensory hair cells. Upon damage, hair cells are extruded and an associated cell type, the supporting cell is transformed into a hair cell. The mechanisms that can trigger regeneration are not known. Using mosaic deletion of the hair cell master gene, Atoh1, in the embryonic avian inner ear, we find that despite hair cells depletion at E9, by E12, hair cell number is restored in sensory epithelium. Our study suggests a homeostatic mechanism can restores hair cell number in the basilar papilla, that is activated when juxtracrine signalling is disrupted. Restoration of hair cell numbers during development may mirror regenerative processes, and our work provides insights into the mechanisms that trigger regeneration. [Display omitted] • Mosaic deletion of Atoh1 in the chick depletes hair cell number at E9. • Hair cells are restored by E12, suggesting a homoeostatic mechanism that regulates hair cell number. • Explant studies show a role for Notch and Wnt signalling in HC restoration. [ABSTRACT FROM AUTHOR]

Mechanosensory hair cells of the inner ears and lateral line of vertebrates display heightened vulnerability to environmental insult, with damage resulting in hearing and balance disorders. An important example is hair cell loss due to exposure to toxic agents including therapeutic drugs such as the aminoglycoside antibiotics neomycin and gentamicin and antineoplastic agents. We describe two distinct cellular pathways for aminoglycoside-induced hair cell death in zebrafish lateral line hair cells. Neomycin exposure results in death from acute exposure with most cells dying within 1 h of exposure. By contrast, exposure to gentamicin results primarily in delayed hair cell death, taking up to 24 h for maximal effect. Washout experiments demonstrate that delayed death does not require continuous exposure, demonstrating two mechanisms where downstream responses differ in their timing. Acute damage is associated with mitochondrial calcium fluxes and can be alleviated by the mitochondrially-targeted antioxidant mitoTEMPO, while delayed death is independent of these factors. Conversely delayed death is associated with lysosomal accumulation and is reduced by altering endolysosomal function, while acute death is not sensitive to lysosomal manipulations. These experiments reveal the complexity of responses of hair cells to closely related compounds, suggesting that intervention focusing on early events rather than specific death pathways may be a successful therapeutic strategy. [ABSTRACT FROM AUTHOR]

The inner ear is a complex organ containing highly specialised cell types and structures that are critical for sensing sound and movement. In vivo , the inner ear is difficult to study due to the osseous nature of the otic capsule and its encapsulation within an intricate bony labyrinth. As such, mammalian inner ear explants are an invaluable tool for the study and manipulation of the complex intercellular connections, structures, and cell types within this specialised organ. The greatest strength of this technique is that the complete organ of Corti, or peripheral vestibular organs including hair cells, supporting cells and accompanying neurons, is maintained in its in situ form. The greatest weakness of in vitro hair cell preparations is the short time frame in which the explanted tissue remains viable. Yet, cochlear explants have proven to be an excellent experimental model for understanding the fundamental aspects of auditory biology, substantiated by their use for over 40 years. In this protocol, we present a modernised inner ear explant technique that employs organotypic cell culture inserts and serum free media. This approach decreases the likelihood of explant damage by eliminating the need for adhesive substances. Serum free media also restricts excessive cellular outgrowth and inter-experimental variability, both of which are side effects of exogenous serum addition to cell cultures. The protocol described can be applied to culture both cochlear and vestibular explants from various mammals. Example outcomes are demonstrated by immunohistochemistry, hair cell quantification, and electrophysiological recordings to validate the versatility and viability of the protocol. [ABSTRACT FROM AUTHOR]

Conventional acoustic sensors used in human–machine interfaces often face challenges such as power supply requirements, limited sensitivity, and inability to tune their frequency response. A self‐powered, highly sensitive, and frequency‐tunable triboelectric acoustic sensor inspired by the human cochlea is introduced. By mimicking hair cells in the organ of Corti, a tapered microhair‐structured ferroelectric poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) and barium titanate nanoparticle (BTNP) composite film is proposed, which demonstrates a 16‐fold increase in triboelectric output voltage (1.3 V) compared to a planar one at 2.8 Pa. Furthermore, inspired by the frequency selectivity of the basilar membrane with gradient structural variations, integrating a mass‐beam diaphragm is proposed with varying kirigami length and circular mass diameter that enables precise tuning of the resonance frequency of the sensor, resulting in a 32 times improvement in sensitivity (860 mV Pa−1) compared to a nonbiomimetic sensor (28 mV Pa−1) and an expanded dynamic range. The proposed sensor differentiates between human voices with different frequencies. A robotic hand integrated with the sensor responds to acoustic stimuli with programmed hand gestures, which highlights its potential in acoustic human–machine interfaces. The biomimetic approach to developing a self‐powered, highly sensitive, and frequency‐tunable acoustic sensor offers new possibilities for intuitive and immersive human–machine interfaces. [ABSTRACT FROM AUTHOR]

Background: The use of mesenchymal stem cells (MSCs) is recognized as a promising strategy for the treatment of androgenetic alopecia (AGA). However, the underlying mechanism remains to be explored. Here, we evaluated the therapeutic effects and potential mechanisms of the use of human umbilical cord mesenchymal stem cells (hUCMSCs) in dihydrotestosterone (DHT)-induced AGA models in vivo and in vitro. Methods: Intradermal transplantation of hUCMSCs was performed in AGA model mice and therapeutic effects were evaluated using histological and immunofluorescence staining. Transwell assays were used for co-culture of hUCMSCs and dermal papilla cells (DPCs), and communication was assessed using RT-qPCR, immunofluorescence, and apoptosis analysis. Interactions between DPCs and hair follicle stem cells (HFSCs) were investigated using RT-qPCR, EdU assays, and cell cycle analysis. Results: Treatment of AGA mice with hUCMSCs promoted hair growth, HFs density, skin thickness, and anagen phase activation, while inhibiting DPCs apoptosis, and promoting HFSCs proliferation. In vitro, hUCMSCs activated Wnt/β-catenin signaling in DPCs via Wntless (Wls), while stimulating growth factor secretion and HFSCs proliferation. Blocking β-catenin degradation with MSAB increased DPCs apoptosis, reduced growth factor secretion, and retarded HFSCs proliferation. Conclusion: hUCMSCs promoted hair regeneration in AGA model mice. This was found to be dependent on reducing DPCs apoptosis, thereby relieving the inhibitory effects of DPCs on the growth of HFSCs. The activation of the Wnt/β-catenin signaling pathway was shown to play a crucial role in the promotion of hair growth by hUCMSCs in AGA mice. [ABSTRACT FROM AUTHOR]

The invasion of terrestrial ecosystems by tetrapods (c. 375 million years [Ma]) represents one of the major evolutionary transitions in the history of life on Earth. The success of tetrapods on land is linked to evolutionary novelties. Among these, the evolution of a tympanic ear contributed to mitigating the problem of an impedance mismatch between the air and the fluid embedding sound-detecting hair cells in the inner ear. 1,2,3 Pioneering studies advocated that similarities in the tympanic ear of tetrapods could only result from a single origin of this structure in the group, 4,5 an idea later challenged by paleontological and developmental data. 4,6,7,8 Current evidence suggests that this sensory structure evolved independently in amphibians, mammals, and reptiles, 1,6 but it remains uncertain how many times tympanic hearing originated in crown reptiles. 9,10 We combine developmental information with paleontological data to evaluate the evolution of the tympanic ear in reptiles from two complementary perspectives. Phylogenetically informed ancestral reconstruction analyses of a taxonomically broad sample of early reptiles point to the presence of a tympanic membrane as the ancestral condition of the crown group. Consistently, comparative analyses using embryos of lizards and crocodylians reveal similarities, including the formation of the tympanic membrane within the second pharyngeal arch, which has been previously reported for birds. Therefore, both our developmental and paleontological data suggest a single origin for the tympanic middle ear in the group, challenging the current paradigm of multiple acquisitions of tympanic hearing in living reptiles. [Display omitted] • Fossils reveal that the presence of tympanic membrane is ancestral to crown reptiles • The eardrum of lizards and crocodylians develops within the second pharyngeal arch • Fossils and embryos suggest a single origin of the tympanic ear in crown reptiles The tympanic ear is a key trait related to the evolutionary success of tetrapods on land, as it enhances the hearing capabilities of animals in this environment. Bronzati et al. use data from embryonic development and from the fossil record and provide evidence for a single origin of tympanic hearing in the group of living reptiles. [ABSTRACT FROM AUTHOR]

ABCB6 has been implicated in dyschromatosis universalis hereditaria, a condition characterized by hyperpigmented and hypopigmented skin macules. Dyschromatosis universalis hereditaria can also present with hearing loss. Dyschromatosis universalis hereditaria-associated mutations in ABCB6 have been reported, but the role of this protein in the inner ear has not been studied. Here we determine a high-resolution (2.93 Å) cryo-EM structure of ABCB6 and functionally characterized several dyschromatosis universalis hereditaria mutants. We find that the L356P mutant abolishes ABCB6 function, and affirm the underlying loss of ATP binding mechanism using molecular dynamics simulations based on our cryo-EM structure. To test the role of ABCB6 in the inner ear, we characterize Abcb6 (the ABCB6 homolog) in zebrafish. We show that Abcb6 suppression by morpholinos reduces inner ear and lateral line hair cell numbers. Morphants also lack the utricular otolith, which is associated with vestibular function. Co-injecting morpholinos with human ABCB6 mRNA partially rescues the morphant phenotype, suggesting that Abcb6 plays a developmental role in inner ear structures. Further, we show that Abcb6 knockout mice exhibit an increased auditory brainstem response threshold, resulting in reduced hearing sensitivity. Taken together, these data suggest ABCB6 plays a role in inner ear development and function. ABCB6 has been implicated in dyschromatosis universalis hereditaria, a condition that can present with hearing loss. Here, the authors use zebrafish and mice to perform experiments suggesting that ABCB6 plays a role in inner ear development. [ABSTRACT FROM AUTHOR]

The sensory cells that transduce the signals for hearing and balance are highly specialized mechanoreceptors called hair cells that together with supporting cells comprise the sensory epithelia of the inner ear. Loss of hair cells from toxin exposure and age can cause balance disorders and is essentially irreversible due to the inability of mammalian vestibular organs to regenerate physiologically active hair cells. Here, we show substantial regeneration of hair cells in a mouse model of vestibular damage by treatment with a combination of glycogen synthase kinase 3ß and histone deacetylase inhibitors. The drugs stimulated supporting cell proliferation and differentiation into hair cells. The new hair cells were reinnervated by vestibular afferent neurons, rescuing otolith function by restoring head translation-evoked otolith afferent responses and vestibuloocular reflexes. Drugs that regenerate hair cells thus represent a potential therapeutic approach to the treatment of balance disorders. [ABSTRACT FROM AUTHOR]

Otolith organs in the inner ear and neuromasts in the fish lateral-line harbor two populations of hair cells oriented to detect stimuli in opposing directions. The underlying mechanism is highly conserved: the transcription factor EMX2 is regionally expressed in just one hair cell population and acts through the receptor GPR156 to reverse cell orientation relative to the other population. In mouse and zebrafish, loss of Emx2 results in sensory organs that harbor only one hair cell orientation and are not innervated properly. In zebrafish, Emx2 also confers hair cells with reduced mechanosensory properties. Here, we leverage mouse and zebrafish models lacking GPR156 to determine how detecting stimuli of opposing directions serves vestibular function, and whether GPR156 has other roles besides orienting hair cells. We find that otolith organs in Gpr156 mouse mutants have normal zonal organization and normal type I-II hair cell distribution and mechano-electrical transduction properties. In contrast, gpr156 zebrafish mutants lack the smaller mechanically evoked signals that characterize Emx2-positive hair cells. Loss of GPR156 does not affect orientation-selectivity of afferents in mouse utricle or zebrafish neuromasts. Consistent with normal otolith organ anatomy and afferent selectivity, Gpr156 mutant mice do not show overt vestibular dysfunction. Instead, performance on two tests that engage otolith organs is significantly altered - swimming and off-vertical-axis rotation. We conclude that GPR156 relays hair cell orientation and transduction information downstream of EMX2, but not selectivity for direction-specific afferents. These results clarify how molecular mechanisms that confer bi-directionality to sensory organs contribute to function, from single hair cell physiology to animal behavior. [ABSTRACT FROM AUTHOR]

Noise‐induced hearing loss (NIHL), a prevalent sensory disability affecting a majority of the global population, is dominantly induced by mitochondrial dysfunction and oxidative stress, but no effective therapeutic strategy is available. Herein, the potential of a 2D catalytic niobium carbide (Nb2C) MXenzyme is investigated as a nanomedicine for treating NIHL by scavenging reactive oxygen species (ROS). The findings reveal that 2D Nb2C MXenzyme effectively eliminates free radicals, resulting in a substantial reduction of ROS in House Ear Institute‐Organ of Corti 1 (HEI‐OC1) cells treated with hydrogen peroxide (H2O2). Additionally, the 2D Nb2C MXenzyme demonstrates significant protection on hair cells by preventing cytotoxicity and apoptosis induced by H2O2. In vivo experiments further support the efficacy of the 2D Nb2C MXenzyme in restoring hearing impairment caused by extensive noise exposure. Specifically, it restores the raised amplitude of Wave I in auditory brainstem response (ABR) records and promotes the recovery of damaged ribbon synapses in inner hair cells. Notably, the therapeutic effect of the 2D Nb2C MXenzyme is attributed to its ability to suppress cochlear oxidative stress evidenced by immunohistochemical analysis. This research provides a new approach for treating hearing loss‐related ear diseases by utilizing catalytic biomaterials and nanomedicine with enzyme‐mimicking properties. [ABSTRACT FROM AUTHOR]

Purpose: This study investigated the effect of miR-204-5p-mediated silencing of SIRT1 on the development of deafness in C57BL/6 mice and the roles of miR-204-5p and SIRT1 in deafness. Methods: Auditory brainstem response recordings, H&E staining, and immunohistochemistry were used to observe changes in hearing function and cochlear tissue morphology in 2-month-old and 15-month-old C57BL/6 mice. A senescence model was induced using H2O2 in inner ear cells (HEI-OC1). Changes in HEI-OC1 cell proliferation were detected using the CCK-8 assay, whereas flow cytometry was used to detect changes in apoptosis. MiR-204-5p expression was measured via RT‒qPCR. The SIRT1 agonist RSV and a miR-204-5p inhibitor were used to study changes in ER stress (ERS), proliferation, and apoptosis in HEI-OC1 cells. Western blotting was performed to detect changes in ATF4, CHOP, SIRT1, PERK, p-PERK, Bax, and Bcl-2 protein levels. A dual-luciferase reporter gene assay was carried out to assess the ability of miR-204-5p to target SIRT1. Results: Relative miR-204-5p expression levels in the cochleae of aged C57BL/6 mice increased, whereas SIRT1 expression levels decreased, and miR-204-5p and SIRT1 expression levels were negatively correlated. ERS and increased 8-OHDG levels were observed in aged C57BL/6 mice. In a model of inner ear cell aging, H2O2 treatment induced increases in miR-204-5p expression and ERS-mediated apoptosis. MiR-204-5p was found to target SIRT1 and inhibit its expression. SIRT1 activation and a miR-204-5p inhibitor promoted HEI-OC1 cell proliferation and reduced apoptosis. The miR-204-5p inhibitor regulated expression of the ERS proteins PERK, ATF4, and CHOP to upregulate Bcl-2 and downregulate Bax. Conclusion: This study identified the roles of miR-204-5p and SIRT1 in deafness in C57BL/6 mice and investigated the loss of cochlear outer hair cells and the involvement of apoptosis and ERS in deafness. [ABSTRACT FROM AUTHOR]

High altitude is characterized by low oxygen, low pressure, and high radiation. When migrates from low to high altitudes, the body's tissues and organs experience hypoxic stress and will present acoustic adaptation as the protective response. However, the mechanisms of acoustic adaptation at high altitudes remain unclear. In this study, cochlear tissues from Wistar rats were collected at 15, 30, 60, 120, and 180 days after high-altitude migration. Transcriptome sequencing was conducted and DESeq algorithm revealed expression patterns of Differentially Expressed Genes(DEGs) after high altitude migration. Day 60 is a critical stage for cochlear tissue "damage" and "repair" in high-altitude conditions. Transmission Electron Microscopy (TEM) observations of structures also support the findings. A time-series gene co-expression network algorithm was used to investigate gene regulatory patterns and key genes after migration. Immunofluorescence, immunohistochemistry, and qPCR were per-formed for key gene validation and localization. At Day 60, the peak DEG count occurs in rats migrating to high altitude, aligning with the critical phase for cochlear tissue damage and repair at high altitudes. Repair hinges on synaptic plasticity and myelination-linked processes, influencing modules M4 to M6. Module M4's activation gradually diminishes from its peak. However, the 'damage' effect is orchestrated by inflammation-related processes in modules M3 to M5, with module M3's activation also waning. Key gene module M4, pivotal for repair during this pivotal phase, encompasses Sptbn5, Cldn1, Gfra2, and Lims2 as its core genes. Immunohistochemistry reveals Sptbn5's presence in cochlear neurons, hair cells, Schwann cells and stria vascularis tissue. Cldn1 and Gfra2 predominantly localize within the cochlear neuron region. These results may suggest new directions for future research on acoustic acclimatization to high altitude. [ABSTRACT FROM AUTHOR]

ABSTRACT Aims and Objectives Method Results Conclusion The aim of this study is to examine the efficacy and safety of various regenerative medicine treatments, such as cell therapy, platelet‐rich plasma (PRP), plasma‐poor platelet (PPP), plasma‐rich fibrin (PRF), mesenchymal stem cells, stromal vascular fraction (SVF), exosomes, adipose‐derived stem cells (ADSC), and stem cell‐conditioned media (SC‐CM), for treating vitiligo.We conducted a thorough search of major databases such as PubMed, Scopus, and Web of Science, and selected 48 articles based on specific criteria. We used EndNote X8 and Google Sheets to review and extract data from the articles. After analyzing the studies, we categorized them accordingly.This systematic review analyzed 48 articles involving 2186 patients with vitiligo to assess the effectiveness of regenerative medicine treatments. Key findings revealed that methods such as autologous non‐cultured melanocyte‐keratinocyte transplantation and platelet‐rich plasma (PRP) injection exhibited significant repigmentation, particularly when combined with modalities like NB‐UVB phototherapy and laser treatments. Notably, the autologous melanocyte‐keratinocyte transplantation achieved over 50% repigmentation within 9 months, while PRP demonstrated an average repigmentation of 58.7%, especially effective with CO2 laser treatment. Hair follicle‐derived cell transplantation also showed impressive response rates, achieving good to excellent results in up to 93.8% of patients. Side effects were noted in 21 of 28 studies, primarily involving pain, with no serious adverse events reported. The risk of bias assessment indicated that 37.21% of studies were low risk, while 48.84% had high risks overall. These findings suggest that while regenerative medicine holds promise for vitiligo treatment, further clinical trials are necessary to explore additional methods like stromal vascular fraction and exosomes.We have concluded that regenerative medicine plays an effective role in the treatment of vitiligo lesions. Furthermore, this treatment method is safe and does not cause serious complications. It can be used alone or in combination with other methods for treating vitiligo. To advance the treatment of vitiligo, we recommend conducting clinical trials on the unexplored branches of regenerative medicine. [ABSTRACT FROM AUTHOR]

Hearing mediates many behaviours critical for survival in echolocating bats, including foraging and navigation. Although most mammals are susceptible to progressive age-related hearing loss, the evolution of biosonar, which requires the ability to hear low-intensity echoes from outgoing sonar signals, may have selected against the development of hearing deficits in bats. Many echolocating bats exhibit exceptional longevity and rely on acoustic behaviours for survival to old age; however, relatively little is known about the ageing bat auditory system. In this study, we used DNA methylation to estimate the ages of wild-caught big brown bats (Eptesicus fuscus) and measured hearing sensitivity in young and ageing bats using auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). We found no evidence for hearing deficits in bats up to 12.5 years of age, demonstrated by comparable thresholds and similar ABR and DPOAE amplitudes across age groups. We additionally found no significant histological evidence for cochlear ageing, with similar hair cell counts, afferent and efferent innervation patterns in young and ageing bats. Here, we demonstrate that big brown bats show minimal evidence for age-related hearing loss and therefore represent informative models for investigating mechanisms that may preserve hearing function over a long lifetime. [ABSTRACT FROM AUTHOR]

Cochlear outer hair cells (OHCs) play a fundamental role in the hearing sensitivity and frequency selectivity of mammalian hearing and are especially vulnerable to noise-induced damage. The OHCs depend on Ca2+ homeostasis, which is a balance between Ca2+ influx and extrusion, as well as Ca2+ buffering by proteins and organelles. Alterations in OHC Ca2+ homeostasis is not only an immediate response to noise, but also associated with impaired auditory function. However, there is little known about the contribution of Ca2+ buffering proteins and organelles to the vulnerability of OHCs to noise. In this study, we used a knockout (KO) mouse model where oncomodulin (Ocm), the major Ca2+ binding protein preferentially expressed in OHCs, is deleted. We show that Ocm KO mice were more susceptible to noise induced hearing loss compared to wildtype (WT) mice. Following noise exposure (106 dB SPL, 2 h), Ocm KO mice had higher threshold shifts and increased OHC loss and TUNEL staining, compared to age-matched WT mice. Mitochondrial morphology was significantly altered in Ocm KO OHCs compared to WT OHCs. Before noise exposure, Ocm KO OHCs showed decreased mitochondrial abundance, volume, and branching compared to WT OHCs, as measured by immunocytochemical staining of outer mitochondrial membrane protein, TOM20. Following noise exposure, mitochondrial proteins were barely visible in Ocm KO OHCs. Using a mammalian cell culture model of prolonged cytosolic Ca2+ overload, we show that OCM has protective effects against changes in mitochondrial morphology and apoptosis. These experiments suggest that disruption of Ca2+ buffering leads to an increase in noise vulnerability and mitochondrial-associated changes in OHCs. [ABSTRACT FROM AUTHOR]

Background: Cashmere, known as "soft gold", is a highly prized fiber from Cashmere goats, produced by secondary hair follicles. Dermal papilla cells, located at the base of these follicles, regulate the proliferation and differentiation of hair matrix cells, which are essential for hair growth and cashmere formation. Recent studies emphasize the role of microRNAs (miRNAs) in controlling gene expression within these processes. Methods: This study centered on exploring the targeted regulatory interaction between miR-144 and the Lhx2 gene. Utilizing methodologies like miRNA target prediction, luciferase reporter assays, and quantitative PCR, they assessed the interplay between miR-144 and Lhx2. Dermal papilla cells derived from Cashmere goats were cultured and transfected with either miR-144 mimics or inhibitors to observe the subsequent effects on Lhx2 expression. Results: The results demonstrated that miR-144 directly targets the Lhx2 gene by binding to its mRNA, leading to a decrease in Lhx2 expression. This modulation of Lhx2 levels influenced the behavior of dermal papilla cells, affecting their ability to regulate hair matrix cell proliferation and differentiation. Consequently, the manipulation of miR-144 levels had a significant impact on the growth cycle of cashmere wool. Conclusions: The findings suggest miR-144 regulates hair follicle dynamics by targeting Lhx2, offering insights into hair growth mechanisms. This could lead to innovations in enhancing cashmere production, fleece quality, and addressing hair growth disorders. Future research may focus on adjusting miR-144 levels to optimize Lhx2 expression and promote hair follicle activity. [ABSTRACT FROM AUTHOR]

The article discusses Lupus Miliaris Disseminatus Faciei (LMDF), a rare inflammatory skin condition primarily affecting the face. Reflectance confocal microscopy (RCM) was used to study the skin lesions of seven patients with LMDF, revealing specific features such as inflammatory cells, granulomas, and dilated vessels in the dermis. The study aimed to describe the RCM features of LMDF and their correlation with pathology, providing valuable insights for diagnosis and treatment. Further research is needed to fully characterize the RCM findings in LMDF. [Extracted from the article]

Objective: Photobiomodulation (PBM) is a noninvasive therapeutic modality with widespread applications for modulating various biological processes. Although the exact mechanisms of action remain uncertain, PBM promotes homeostasis through diverse pathways, including reducing inflammation and enhancing tissue recovery. Hearing loss is irreversible in mammals due to the limited regenerative capacity of cochlear hair cells. Cochlear implants offer a solution by electrically stimulating the auditory nerve, bypassing damaged hair cells in individuals with severe hearing loss. However, postoperative inflammatory responses and cochlear nerve fiber damage can compromise implant efficacy. Materials and Methods: We investigated current strategies to minimize secondary cochlear damage after cochlear implantation and evaluated the potential of PBM as an adjuvant therapeutic approach. Results: The auditory cell protective effects of PBM could significantly enhance the performance of EAS devices in individuals with residual hearing. Further, postoperative CI is accompanied by an inflammatory response characterized by the upregulation of specific cytokines. Conclusion: Considering the neuroregenerative potential of PBM, its application as a neuroprotective strategy warrants further validation. [ABSTRACT FROM AUTHOR]

Notch signaling patterns the cochlear organ of Corti, and individuals with the JAG1/NOTCH2-related genetic disorder Alagille syndrome can thus experience hearing loss. We investigated the function of Jag1 in cochlear patterning and signaling using Jag1Ndr/Ndr mice, which are a model of Alagille syndrome. Jag1Ndr/Ndr mice exhibited expected vestibular and auditory deficits, a dose-dependent increase in ectopic inner hair cells, and a reduction in outer hair cells. Single cell RNA sequencing of the organ of Corti demonstrated a global dysregulation of genes associated with inner ear development and deafness. Analysis of individual cell types further revealed that Jag1 represses Notch activation in lateral supporting cells and demonstrated a function for Jag1 in gene regulation and development of outer hair cells. Surprisingly, ectopic 'outer hair cell-like' cells were present in the medial compartment and pillar cell region of Jag1Ndr/Ndr cochleae, yet they exhibited location-dependent expression of the inner hair cell fate-determinant Tbx2, suggesting Jag1 is required for Tbx2 to drive inner hair cell commitment. This study thus identifies new roles for Jag1 in supporting cells, and in outer hair cell specification and positioning. [ABSTRACT FROM AUTHOR]

The development of sensory hair cells (HCs) is closely linked to hearing loss. There are still many unidentified genes that may play a crucial role in HC development and function. Glutamine synthetase, Glul, is expressed in sensory hair cells and auditory organs. However, the role of the Glul gene family in the auditory system remains largely unexplored. This study aims to investigate the function of the Glul gene family in the auditory system. The expression patterns of the glul gene family were examined via in situ hybridization in zebrafish embryos. It was revealed that the expression of glula occurred in the otic vesicle, while glulb was expressed in the neuromast. In contrast, glulc did not exhibit any discernible signal. glula loss of function caused abnormal otolith formation and reduced hair cell number in otic vesicles, while glulb knockdown caused a decrease in HC number in both neuromasts and otic vesicles and impaired auditory function. Furthermore, we found that the knockdown of glulb induces apoptosis of hair cells. Transcriptomic analysis of zebrafish with glula and glulb knockdown revealed significant alterations in the expression of many genes associated with auditory organs. The current study sheds light on the requirement of glula and glulb in zebrafish hair cell formation and auditory function. [ABSTRACT FROM AUTHOR]

A series of differentially expressed circular RNAs (circRNAs), microRNAs (miRNAs), and messenger RNAs (mRNAs) were identified through sequencing in the hair follicle tissues of Hu sheep with small-waved and straight wool patterns. Based on these findings, the circCSPP1-miR-10a-BMP7 (Bone Morphogenetic Protein 7) regulatory network was constructed. The preliminary study highlighted that miR-10a and the BMP7 gene exhibited not only significant differential expression across hair follicle tissues with different patterns in Hu sheep but also had an impact on the proliferation of hair papilla cells. The proliferation of hair papilla cells is intricately linked to hair follicle development and growth. Consequently, we selected the circCSPP1-miR-10a-BMP7 regulatory network to validate its role in promoting hair papilla cell proliferation in Hu sheep. Firstly, the authenticity of circCSPP1 was successfully confirmed through RNase R digestion and reverse primer amplification. Additionally, nucleoplasmic localization analysis determined that circCSPP1 was predominantly distributed in the cytoplasm. Using the dual-luciferase gene reporter system, we verified the targeting relationship between circCSPP1 and miR-10a, building upon our previous validation of the miR-10a-BMP7 interaction. This clarified the competing endogenous RNA (ceRNA) mechanism within the circCSPP1-miR-10a-BMP7. Furthermore, rescue experiments confirmed that circCSPP1 competitively binds to miR-10a, thereby regulating BMP7 expression and influencing the proliferation of hair papilla cells in Hu sheep. This discovery provides a solid foundation for future investigations into the mechanisms underlying wool curvature and the formation of lambskin patterns, offering insights into the complex regulatory networks that govern these phenotypic traits in Hu sheep. [ABSTRACT FROM AUTHOR]

Cisplatin-induced ototoxicity occurs in approximately half of patients treated with cisplatin, and pediatric patients are more likely to be affected than adults. The oxidative stress elicited by cisplatin is a key contributor to the pathogenesis of ototoxicity. Notoginsenoside R1 (NGR1), the main bioactive compound of Panax notoginseng saponins, has antioxidant and antiapoptotic effects. This study investigated the ability of NGR1 to protect against cisplatin-induced damage in auditory HEI-OC1 cells and neonatal murine cochlear explants. The viability of HEI-OC1 cells treated with NGR1 and cisplatin was greater than that of cells treated with cisplatin alone. The results of Western blots and immunostaining for cleaved caspase-3 revealed that the level of cleaved caspase-3 in the cells treated with cisplatin was repressed by NGR1. NGR1 attenuated cisplatin-induced cytotoxicity in HEI-OC1 cells. Intracellular reactive oxygen species (ROS) were detected with a DCFDA assay and immunostaining for 4-HNE. The result revealed that its expression was induced by cisplatin and was significantly reduced by NGR1. Moreover, NGR1 can promote heme oxygenase-1 (HO-1) expression at both the mRNA and protein levels. ZNPPIX, an HO-1 inhibitor, was administered to cisplatin-treated cells to investigate the role of HO-1 in the protective effect of NGR1. The suppression of HO-1 activity by ZNPPIX markedly abolished the protective effect of NGR1 on cisplatin-treated cells. Therefore, NGR1 protects cells from cisplatin-induced damage by activating HO-1 and its antioxidative activity. In cochlear explants, NGR1 protects cochlear hair cells and attenuates cisplatin-induced ototoxicity by inhibiting ROS generation. In the group treated with cisplatin alone, prominent loss of outer hair cells and severe damage to the structure of the stereociliary bundles of inner and outer hair cells were observed. Compared with the group treated with cisplatin alone, less loss of outer hair cells (p = 0.009) and better preservation of the stereociliary bundles of hair cells were observed in the group treated with cisplatin and NGR1. In conclusion, these findings indicate that NGR1 can protect against cisplatin-induced ototoxicity by inducing HO-1 expression and suppressing oxidative stress. [ABSTRACT FROM AUTHOR]

Background Information: Microvilli are finger‐like, straight, and stable cellular protrusions that are filled with F‐actin and present a stereotypical length. They are present in a broad range of cell types across the animal tree of life and mediate several fundamental functions, including nutrient absorption, photosensation, and mechanosensation. Therefore, understanding the origin and evolution of microvilli is key to reconstructing the evolution of animal cellular form and function. Here, we review the current state of knowledge on microvilli evolution and perform a bioinformatic survey of the conservation of genes encoding microvillar proteins in animals and their unicellular relatives. Results: We first present a detailed description of mammalian microvilli based on two well‐studied examples, the brush border microvilli of enterocytes and the stereocilia of hair cells. We also survey the broader diversity of microvilli and discuss similarities and differences between microvilli and filopodia. Based on our bioinformatic survey coupled with carefully reconstructed molecular phylogenies, we reconstitute the order of evolutionary appearance of microvillar proteins. We document the stepwise evolutionary assembly of the "molecular microvillar toolkit" with notable bursts of innovation at two key nodes: the last common filozoan ancestor (correlated with the evolution of microvilli distinct from filopodia) and the last common choanozoan ancestor (correlated with the emergence of inter‐microvillar adhesions). Conclusion and Significance: We conclude with a scenario for the evolution of microvilli from filopodia‐like ancestral structures in unicellular precursors of animals. [ABSTRACT FROM AUTHOR]

Background: Preclinical cell tracking is enhanced with a multimodal imaging approach. Bioluminescence imaging (BLI) is a highly sensitive optical modality that relies on engineering cells to constitutively express a luciferase gene. Magnetic particle imaging (MPI) is a newer imaging modality that directly detects superparamagnetic iron oxide (SPIO) particles used to label cells. Here, we compare BLI and MPI for imaging cells in vitro and in vivo. Methods: Mouse 4T1 breast carcinoma cells were transduced to express firefly luciferase, labeled with SPIO (ProMag), and imaged as cell samples after subcutaneous injection into mice. Results: For cell samples, the BLI and MPI signals were strongly correlated with cell number. Both modalities presented limitations for imaging cells in vivo. For BLI, weak signal penetration, signal attenuation, and scattering prevented the detection of cells for mice with hair and for cells far from the tissue surface. For MPI, background signals obscured the detection of low cell numbers due to the limited dynamic range, and cell numbers could not be accurately quantified from in vivo images. Conclusions: It is important to understand the shortcomings of these imaging modalities to develop strategies to improve cellular detection sensitivity. [ABSTRACT FROM AUTHOR]

Aminoglycoside antibiotics, including gentamicin (GM), induce delayed ototoxic effects such as hearing loss after prolonged use, which results from the death of hair cells. However, the mechanisms underlying the ototoxicity of aminoglycosides warrant further investigation, and there are currently no effective drugs in the clinical setting. Herein, the therapeutic effect of the flavonoid compound rutin against the ototoxic effects of GM in zebrafish hair cells was investigated. Animals incubated with rutin (100–400 µmol/L) were protected against the pernicious effects of GM (200 µmol/L). We found that rutin improves hearing behavior in zebrafish, and rutin was effective in reducing the number of Tunel-positive cells in the neuromasts of the zebrafish lateral line and promoting cell proliferation after exposure to GM. Subsequently, rutin exerted a protective effect against GM-induced cell death in HEI-OC1 cells and could limit the production of cytosolic reactive oxygen species (ROS) and diminish the percentage of apoptotic cells. Additionally, the results of the proteomic analysis revealed that rutin could effectively inhibit the expression of necroptosis and apoptosis related genes. Meanwhile, molecular docking analysis revealed a high linking activity between the molecular docking of rutin and STAT1 proteins. The protection of zebrafish hair cells or HEI-OC1 cells from GM-induced ototoxicity by rutin was attenuated by the introduction of STAT1 activator. Finally, we demonstrated that rutin significantly improves the bacteriostatic effect of GM by in vitro experiments, emphasising its clinical application value. In summary, these results collectively unravel a novel therapeutic role for rutin as an otoprotective drug against the adverse effects of GM. [ABSTRACT FROM AUTHOR]

Morphological mouse phenotyping plays a pivotal role in the translational setting and even more in the area of auditory research, where mouse is a central model organism due to the evolutionary genetic relationship and morpho‐functional analogies with the human auditory system. However, some results obtained in murine models cannot be translated to humans due to the inadequate description of experimental conditions underlying poor reproducibility. We approach the characterization of the aging process of the mouse cochlea in animals up to 18 months of age belonging to two of the most used outbred (CD1) and inbred (C57BL/6N) strains. Striving to reduce any environmental variable we performed our study compliantly to the ARRIVE guidelines. We integrated instrumental data (auditory brainstem response test), with morphological analyses to correlate functional discrepancies to morphological changes and track the differences in the evolution of sensorineural hearing loss in the two strains. We featured the localization of Gipc3, Myosin VIIa, and TMC1 in hair cells of the Corti organ as well as NF 200 and the density of type I neuron in the spiral ganglion. We outlined age‐related hearing loss (ARHL) in both strains, and a clear drop in the selected marker localization. However, in CD1 we detected a different trend allowing the identification of potential strain‐specific mechanisms, namely an increase in myosin VIIa in 6 months aging mice in comparison to 2 months old animals. Our findings represent an asset to investigate the strain‐dependent physiological trigger of ARHL providing new insights in the translational area. [ABSTRACT FROM AUTHOR]

Introduction: Hair cells (HCs) are the sensory receptors of the auditory and vestibular systems in the inner ears of vertebrates that selectively transduce mechanical stimuli into electrical activity. Although all HCs have the hallmark stereocilia bundle for mechanotransduction, HCs in non-mammals and mammals differ in their molecular specialization in the apical, basolateral, and synaptic membranes. HCs of non-mammals, such as zebrafish (zHCs), are electrically tuned to specific frequencies and possess an active process in the stereocilia bundle to amplify sound signals. Mammalian HCs, in contrast, are not electrically tuned and achieve amplification by somatic motility of outer HCs (OHCs). Methods: To understand the genetic mechanisms underlying differences between adult zebrafish and mammalian HCs, we compared their RNA-seq- characterized transcriptomes, focusing on protein-coding orthologous genes related to HC specialization. Results: There was considerable shared expression of gene orthologs among the HCs, including those genes associated with mechanotransduction, ion transport/channels, and synaptic signaling. However, there were some notable differences in expression among zHCs, OHCs, and inner HCs (IHCs), which likely underlie the distinctive physiological properties of each cell type. For example, OHCs highly express Slc26a5 which encodes the motor protein prestin that contributes toOHC electromotility. However, zHCs have only weak expression of slc26a5, and subsequently showed no voltage-dependent electromotility when measured. Notably, the zHCs expressed more paralogous genes including those associated with HC-specific functions and transcriptional activity, though it is unknown whether they have functions similar to their mammalian counterparts. There was overlap in the expressed genes associated with a known hearing phenotype. Discussion: Our analyses unveil substantial differences in gene expression patterns thatmay explain phenotypic specialization of zebrafish andmouse HCs. This dataset also includes several protein-coding genes to further the functional characterization of HCs and study of HC evolution from non-mammals to mammals. [ABSTRACT FROM AUTHOR]

Noise-induced cochlear synaptopathy is characterized by irreversible loss of synapses between inner hair cells (IHCs) and spiral ganglion neurons (SGNs) despite normal hearing thresholds. We analyzed hearing performance and cochlear structure in C57BL/6 N mice exposed to 100, 106, or 112 dB SPL broadband noise (8–16 kHz) for 2 h. Auditory brainstem responses (ABRs) were assessed before, directly after, and up to 28 days post-trauma. Finally, the number, size, and pairing of IHC presynaptic (CtBP2-positive) ribbons and postsynaptic AMPA receptor scaffold (Homer1-positive) clusters were analyzed along the cochlea. Four weeks after the 100 dB SPL trauma, a permanent threshold shift (PTS) was observed at 45 kHz, which after the higher traumata extended toward middle to low frequencies. Loss in ABR wave I amplitudes scaled with trauma strength indicating loss of functional IHC synaptic connections. Latencies of wave I mostly increased with trauma strength. No trauma-related OHC loss was found. The number of synaptic pairs was reduced in the midbasal and basal cochlear region in all trauma conditions, with ribbon loss amounting up to 46% of control. Ribbons surviving the trauma were paired, whereas 4–6 unpaired postsynapses/IHC were found in the medial, midbasal, and basal regions irrespective of trauma strength, contrasting findings in CBA/CaJ mice. Our data confirm the susceptibility of ribbon synapses and ABR wave I amplitudes to a noise trauma of 100 dB SPL or larger. Notably, peripheral dendrites bearing IHC postsynapses were less vulnerable than presynaptic ribbons in C57BL/6 N mice. [ABSTRACT FROM AUTHOR]

The capabilities of the human ear are remarkable. We can normally detect acoustic stimuli down to a threshold sound-pressure level of 0 dB (decibels) at the entrance to the external ear, which elicits eardrum vibrations in the picometer range. From this threshold up to the onset of pain, 120 dB, our ears can encompass sounds that differ in power by a trillionfold. The comprehension of speech and enjoyment of music result from our ability to distinguish between tones that differ in frequency by only 0.2%. All these capabilities vanish upon damage to the ear’s receptors, the mechanoreceptive sensory hair cells. Each cochlea, the auditory organ of the inner ear, contains some 16,000 such cells that are frequency-tuned between ∼20 Hz (cycles per second) and 20,000 Hz. Remarkably enough, hair cells do not simply capture sound energy: they can also exhibit an active process whereby sound signals are amplified, tuned, and scaled. This article describes the active process in detail and offers evidence that its striking features emerge from the operation of hair cells on the brink of an oscillatory instability—one example of the critical phenomena that are widespread in physics. [ABSTRACT FROM AUTHOR]