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

Interplay between noise-induced sensorineural hearing loss and hypertension: pathophysiological mechanisms and therapeutic prospects

More than 5% of the global population suffers from disabling hearing loss, primarily sensorineural hearing loss (SNHL). SNHL is often caused by factors such as vascular disorders, viral infections, ototoxic drugs, systemic inflammation, age-related labyrinthine membrane degeneration, and noise-induced hearing loss (NIHL). NIHL, in particular, leads to changes in blood-labyrinth-barrier (BLB) physiology, increased permeability, and various health issues, including cardiovascular disease, hypertension, diabetes, neurological disorders, and adverse reproductive outcomes. Recent advances in neuromodulation and vector-based approaches offer hope for overcoming biological barriers such as the BLB in the development of innovative treatments. Computational methods, including molecular docking, molecular dynamics simulations, QSAR/QSPR analysis with machine/deep learning algorithms, and network pharmacology, hold potential for identifying drug candidates and optimizing their interactions with BLB transporters, such as the glutamate transporter. This paper provides an overview of NIHL, focusing on its pathophysiology; its impact on membrane transporters, ion channels, and BLB structures; and associated symptoms, comorbidities, and emerging therapeutic approaches. Recent advancements in neuromodulation and vector-based strategies show great promise in overcoming biological barriers such as BLB, facilitating the development of innovative treatment options. The primary aim of this review is to examine NIHL in detail and explore its underlying mechanisms, physiological effects, and cutting-edge therapeutic strategies for its effective management and prevention.

Increased risk of chronic diseases and multimorbidity in middle-aged and elderly individuals with early vision, hearing, or dual sensory impairments: insights from prospective cohort studies and Mendelian randomization analysis

BACKGROUND

Sensory impairments (SI), including vision (VI), hearing (HI), and dual sensory impairments (DSI), are prevalent with aging, but their impact on disease risk remains unclear. This study investigates the epidemiological and genetic associations between SIs and 10 chronic disease categories and multimorbidity.

METHODS

Using the CHARLS study, participants were classified by their self-reported VI/HI/DSI status in 2011 and 2013 into groups: "new onset, remission, persistent, and no SI." Their chronic disease incidence was tracked until 2018 in sub-cohorts respectively. Mendelian randomization (MR) analyses used genetic instruments from UK Biobank GWAS data on 88,250/504,307 individuals for vision/hearing loss, with outcome datasets from consortia including FinnGen, DIAMANTE, CKDGen, PGC, GWAS Catalog, and International Parkinson's Disease Genomics Consortium.

RESULTS

The cohort study revealed that persistent HI significantly increased the risk of heart disease (P < 0.001, HR 1.63, 95% CI 1.31-2.03), stroke (P 0.004, HR 1.59, 95% CI 1.16-2.18), chronic lung disease (P 0.002, HR 1.53, 95% CI 1.17-1.99), and emotional, nervous, or psychiatric problems (P 0.016, HR 2.03, 95% CI 1.14-3.60). Persistent VI was significantly associated with diabetes or high blood sugar (DM/Hglu) (P 0.012, HR 1.63, 95% CI 1.11-2.38) and chronic lung disease (P 0.042, HR 1.53, 95% CI 1.02-2.31). MR confirmed these strong or suggestive associations, indicating that HI significantly increased the risk of cardiovascular and cerebrovascular events by 61-170%, bronchitis by 160%, and schizophrenia by 36%. In addition, VI significantly raised the risk of hyperglycemia or diabetes by 2-4% and the risk of lung function decline. Additionally, cohort studies confirmed that early DSI significantly raised the risk of multiple diseases, while MR identified genetic links between VI and hepatic failure, Parkinson's, and Alzheimer's disease, and between HI and hypertension, chronic kidney disease, and renal failure.

CONCLUSIONS

This study provides evidence from epidemiological or genetic perspectives demonstrates that early exposure to HI/VI/DSI increases the risk of developing chronic diseases. These findings underscore the need for continuous monitoring and timely intervention for SI to manage chronic disease risks in aging populations.

Molecular differences between young and mature stria vascularis from organotypic explants and transcriptomics

The stria vascularis (SV) is an essential component of the inner ear that regulates the ionic environment required for hearing. SV degeneration disrupts cochlear homeostasis, leading to irreversible hearing loss, yet a comprehensive understanding of the SV, and consequently therapeutic availability for SV degeneration, is lacking. We developed a whole-tissue explant model from neonatal and mature mice to create a platform for advancing SV research. We validated our model by demonstrating that the proliferative behavior of the SV in vitro mimics SV in vivo. We also provided evidence for pharmacological experimentation by investigating the role of Wnt/β-catenin signaling in SV proliferation. Finally, we performed single-cell RNA sequencing from in vivo neonatal and mature mouse SV and surrounding tissue and revealed key genes and pathways that may play a role in SV proliferation and maintenance. Together, our results contribute new insights into investigating biological solutions for SV-associated hearing loss.

LDHA-mediated glycolysis in stria vascularis endothelial cells regulates macrophages function through CX3CL1-CX3CR1 pathway in noise-induced oxidative stress

According to the World Health Organization, more than 12% of the world's population suffers from noise-induced hearing loss (NIHL). Oxidative stress-mediated damage to the stria vascularis (SV) is one of the pathogenic mechanisms of NIHL. Recent studies indicate that glycolysis plays a critical role in endothelial cells (ECs)-related diseases. However, the specific role of glycolysis in dysfunction of SV-ECs remain largely unknown. In this study, we investigated the effects of glycolysis on SV-ECs in vitro and on the SV in vivo. Our previous research identified the glycolysis pathway as a potential mechanism underlying the SV-ECs injuries induced by oxidative stress. We further examined the expression levels of glycolytic genes in SV-ECs under H2O2 stimulation and in noise-exposed mice. We found that the gene and protein expression levels of glycolytic-related enzyme LDHA significantly decreased at early phase after oxidative stress injury both in vitro and in vivo, and exhibited anti-inflammatory effects on macrophages (Mφ). Moreover, we analyzed the differential secretomes of SV-ECs with and without inhibition of LDHA using LC-MS/MS technology, identifying CX3CL1 as a candidate mediator for cellular communication between SV-ECs and Mφ. We found that CX3CL1 secretion from SV-ECs was decreased following LDHA inhibition and exhibited anti-inflammatory effects on Mφ via the CX3CR1 pathway. Similarly, the pro-inflammatory effect of LDHA-overexpressing SV-ECs was attenuated following inhibition of CX3CL1. In conclusion, our study revealed that glycolysis-related LDHA was reduced in oxidative stress-induced SV-ECs, and that LDHA inhibition in SV-ECs elicited anti-inflammatory effects on Mφ, at least partially through the CX3CL1-CX3CR1 pathway. These findings suggest that LDHA represent a novel therapeutic strategy for the treatment of NIHL.

A biomarker framework for auditory system aging: the Aging Biomarker Consortium consensus statement

Hearing is one of the most vital sensory functions in human beings and a crucial means of perceiving and acquiring information from the natural environment. The advancement of human society is closely linked to the development of language, with hearing serving as the foundation for verbal communication. As individuals age, the deterioration of the auditory system becomes a significant factor contributing to sensory impairments in the elderly. In addition to hearing loss, the aging of the auditory system is also associated with cognitive decline and psychosocial disorders, which severely impact the quality of life for older adults. Currently, there are no effective treatments or interventions available for addressing the aging of the auditory system. Therefore, identifying biomarkers of the auditory system aging is of great significance. The Aging Biomarker Consortium of China has conducted a comprehensive evaluation of aging biomarkers in the auditory system, focusing on three dimensions: morphological, functional, and humoral biomarkers. This initiative aims to establish a foundation for assessing the degree of aging in the auditory system and to promote the management of auditory health in an aging society, ultimately enhancing the auditory health of the elderly population both in China and globally.

Gene therapy for hereditary hearing loss

Gene therapy is a technique by which exogenous genetic material is introduced into target cells to treat or prevent diseases caused by genetic mutations. Hearing loss is the most common sensory disorder. Genetic factors contribute to approximately 50 % of all cases of profound hearing loss, and more than 150 independent genes have been reported as associated with hearing loss. Recent advances in CRISPR/Cas based gene-editing tools have facilitated the development of gene therapies for hereditary hearing loss (HHL). Viral delivery vectors, and especially adeno-associated virus (AAV) vectors, have been demonstrated as safe and efficient carriers for the delivery of transgenes into inner ear cells in animal models. More importantly, AAV-mediated gene therapy can restore hearing in some children with hereditary deafness. However, there are many different types of HHL that need to be identified and evaluated to determine appropriate gene therapy options. In the present review, we summarize recent animal model-based advances in gene therapy for HHL, as well as gene therapy strategies, gene-editing tools, delivery vectors, and administration routes. We also discuss the strengths and limitations of different gene therapy methods and describe future challenges for the eventual clinical application of gene therapy for HHL.

Pesticide metabolite 3, 5, 6-trichloro-2-pyridinol causes massive damage to the cochlea resulting in hearing loss in adult mice

Pesticides are a group of extensively used man-made chemicals with high toxicity and strong residues, which are closely related to hearing health. Pesticide metabolite 3, 5, 6-Trichloro-2-pyridinol (TCP) exposure leads to neurotoxicity and auditory cell toxicity. However, whether TCP causes damage to hearing in adult mice is not clear. In this study, adult male C57BL/6 mice continuously exposed to TCP for 21 days showed a dose-dependent elevation of hearing threshold. Outer hair cells and spiral neuron cells were lost in a dose-dependent manner. Type I and V of spiral ligament were severely shrunk and stria vascularis were thinned in mice after 50 and 150 mg/kg TCP exposure. Similarly, ROS levels in the cochlea were significantly increased whereas the activities of anti-oxidation enzymes were decreased after TCP exposure. The expression level of Na+/K+ ATPase was decreased, resulting in cochlear potential disruption. Levels of inflammatory factors (TNF-α and IL-1β), γ-H2AX, and pro-apoptotic-related factors (Bax and cleaved-Caspase 3) were elevated, respectively. These results suggest that TCP can cause oxidative stress, inflammation, and imbalance of cochlear potential in the cochlea, induce cochlear DNA damage and apoptosis, and cause cochlear morphological changes, eventually leading to impaired hearing function.

The Role of Pericytes in Inner Ear Disorders: A Comprehensive Review

Inner ear disorders, including sensorineural hearing loss, Meniere's disease, and vestibular neuritis, are prevalent conditions that significantly impact the quality of life. Despite their high incidence, the underlying pathophysiology of these disorders remains elusive, and current treatment options are often inadequate. Emerging evidence suggests that pericytes, a type of vascular mural cell specialized to maintain the integrity and function of the microvasculature, may play a crucial role in the development and progression of inner ear disorders. The pericytes are present in the microvasculature of both the cochlea and the vestibular system, where they regulate blood flow, maintain the blood-labyrinth barrier, facilitate angiogenesis, and provide trophic support to neurons. Understanding their role in inner ear disorders may provide valuable insights into the pathophysiology of these conditions and lead to the development of novel diagnostic and therapeutic strategies, improving the standard of living. This comprehensive review aims to provide a detailed overview of the role of pericytes in inner ear disorders, highlighting the anatomy and physiology in the microvasculature, and analyzing the mechanisms that contribute to the development of the disorders. Furthermore, we explore the potential pericyte-targeted therapies, including antioxidant, anti-inflammatory, and angiogenic approaches, as well as gene therapy strategies.

Ezetimibe protects against Gentamycin-induced ototoxicity in rats by antioxidants, anti-inflammatory mechanisms, and BDNF upregulation

OBJECTIVE

The threat of hearing loss has become a universal reality. Gentamycin (GM) can lead to ototoxicity and may result in permanent hearing loss. This study aimed to elucidate whether the hypolipidemic drug Ezetimibe (EZE) has a possible underlying mechanism for protecting rats from GM-induced ototoxicity.

METHODS AND RESULTS

30 male Wister albino rats were separated into three groups, ten in each group: control, GM, and GM + EZE. At the end of the experiment, rats underwent hearing threshold evaluation via auditory brainstem response (ABR), carotid artery blood flow velocity (CBV), and resistance (CVR) measurement, in addition to a biochemical assessment of serum malondialdehyde (MDA), nitric oxide (NO), catalase (CAT), hemeOxygenase-1 (HO-1), and tumor necrosis factor-α (TNF-α). Also, real-time PCR was employed to quantify the levels of brain-derived neurotrophic factor (BDNF). Cochlea was also studied via histological and immunohistochemical methods. GM revealed a significant increase in CVR, MDA, NO, and TNF-α and a significant decrease in ABR, CBV, CAT, HO-1, and cochlear BDNF expression. EZE supplementation revealed a significant rise in ARB in addition to CBV and a decline in CVR and protected cochlear tissues via antioxidant, anti-inflammatory, and antiapoptotic mechanisms via downregulating Caspase-3 immunoreaction, upregulating proliferating cellular nuclear antigen (PCNA) immunoreaction, and upregulating of the cochlear BDNF expression. Correlations were significantly negative between BDNF and MDA, NO, TNF-α, COX 2, and caspase-3 immunoreaction and significantly positive with CAT, HO-1, and PCNA immunoreaction.

DISCUSSION

EZE can safeguard inner ear tissues from GM via antioxidant, anti-inflammatory, and antiapoptotic mechanisms, as well as upregulation of BDNF mechanisms.

Relationship between Age-Related Hearing Loss and Age-Related Macular Degeneration

BACKGROUND

With the aging of the population, the deterioration of visual and auditory functions amongst the elderly has attracted much attention. Age-related hearing loss (ARHL) and age-related macular degeneration (AMD) are common eye and ear diseases that seriously affect the quality of life of elderly population.

METHODS

This study utilised a whole cohort sampling method, with a total of 713 participants aged 50 years and older in the community from June 2022 to October 2023, resulting in the inclusion of 620 participants. Demographic information was collected from these participants, and eye and hearing examinations were conducted at Ningde Municipal Hospital affiliated of Fujian Medical University. Spearman's correlation analysis was utilised to investigate the association between ARHL and AMD in patients. Multivariate logistic regression analysis was employed to identify the factors influencing ARHL to provide insights for preventing and treating ARHL and AMD in older individuals.

RESULTS

Correlation analysis indicated a significantly positive relationship between ARHL and AMD (P < 0.001). The results showed that age, medical history, AMD and chronic noise exposure were risk factors for ARHL.

CONCLUSIONS

There were 196 cases of AMD in ARHL patients (82.35%). Spearman's correlation analysis revealed that ARHL was associated with AMD; logistic regression analysis revealed that age, medical history, macular degeneration and history of prolonged noise exposure were risk factors for ARHL. Among them, age, medical history (hypertension, hyperlipidaemia and diabetes mellitus), noise and AMD influence the development of ARHL in the elderly population. Therefore, attention should be paid to controlling risk factors in this population to prevent or reduce the development of ARHL.

Pathophysiological processes underlying hidden hearing loss revealed in Kcnt1/2 double knockout mice

Presbycusis is a prevalent condition in older adults characterized by the progressive loss of hearing due to age-related changes in the cochlea, the auditory portion of the inner ear. Many adults also struggle with understanding speech in noise despite having normal auditory thresholds, a condition termed "hidden" hearing loss because it evades standard audiological assessments. Examination of animal models and postmortem human tissue suggests that hidden hearing loss is also associated with age-related changes in the cochlea and may, therefore, precede overt age-related hearing loss. Nevertheless, the pathological mechanisms underlying hidden hearing loss are not understood, which hinders the development of diagnostic biomarkers and effective treatments for age-related hearing loss. To fill these gaps in knowledge, we leveraged a combination of tools, including transcriptomic profiling and morphological and functional assessments, to identify these processes and examine the transition from hidden to overt hearing loss. As a novel approach, we took advantage of a recently characterized model of hidden hearing loss: Kcnt1/2 double knockout mice. Using this model, we find that even before observable morphological pathology, hidden hearing loss is associated with significant alteration in several processes, notably proteostasis, in the cochlear sensorineural structures, and increased susceptibility to overt hearing loss in response to noise exposure and aging. Our findings provide the first insight into the pathophysiology associated with the earliest and, therefore, most treatable stages of hearing loss and provide critical insight directing future investigation of pharmaceutical strategies to slow and possibly prevent overt age-related hearing loss.

SVPath: A Deep Learning Tool for Analysis of Stria Vascularis from Histology Slides

INTRODUCTION

The stria vascularis (SV) may have a significant role in various otologic pathologies. Currently, researchers manually segment and analyze the stria vascularis to measure structural atrophy. Our group developed a tool, SVPath, that uses deep learning to extract and analyze the stria vascularis and its associated capillary bed from whole temporal bone histopathology slides (TBS).

METHODS

This study used an internal dataset of 203 digitized hematoxylin and eosin-stained sections from a normal macaque ear and a separate external validation set of 10 sections from another normal macaque ear. SVPath employed deep learning methods YOLOv8 and nnUnet to detect and segment the SV features from TBS, respectively. The results from this process were analyzed with the SV Analysis Tool (SVAT) to measure SV capillaries and features related to SV morphology, including width, area, and cell count. Once the model was developed, both YOLOv8 and nnUnet were validated on external and internal datasets.

RESULTS

YOLOv8 implementation achieved over 90% accuracy for cochlea and SV detection. nnUnet SV segmentation achieved a DICE score of 0.84-0.95; the capillary bed DICE score was 0.75-0.88. SVAT was applied to compare both the ears used in the study. There was no statistical difference in SV width, SV area, and average area of capillary between the two ears. There was a statistical difference between the two ears for the cell count per SV.

CONCLUSION

The proposed method accurately and efficiently analyzes the SV from temporal histopathology bone slides, creating a platform for researchers to understand the function of the SV further.

Physiological Roles of Eumelanin- and Melanogenesis-Associated Diseases: A Look at the Potentialities of Engineered and Microbial Eumelanin in Clinical Practice

This paper aims to highlight the physiological actions exerted by eumelanin present in several organs/tissues of the human body and to rationalise the often conflicting functional roles played by this biopolymer on the basis of its peculiar properties. Besides pigmentary disorders, a growing number of organ injuries and degenerative pathologies are presently ascribed to the modification of physiological eumelanin levels in terms of alterations in its chemical/structural features, and of a partial loss or uneven distribution of the pigment. The present review analyses the more recent research dedicated to the physiological and pathological actions of eumelanin and provides an insight into some melanogenesis-associated diseases of the skin, eye, ear, and brain, including the most significant neurodegenerative disorders. Also described are the potentialities of therapies based on the localised supply of exogeneous EU and the opportunities that EU produced via synthetic biology offers in order to redesign therapeutical and diagnostic applications.

The Stria Vascularis: Renewed Attention on a Key Player in Age-Related Hearing Loss

Age-related hearing loss (HL), or presbycusis, is a complex and heterogeneous condition, affecting a significant portion of older adults and involving various interacting mechanisms. Metabolic presbycusis, a type of age-related HL, is characterized by the dysfunction of the stria vascularis, which is crucial for maintaining the endocochlear potential necessary for hearing. Although attention on metabolic presbycusis has waned in recent years, research continues to identify strial pathology as a key factor in age-related HL. This narrative review integrates past and recent research, bridging findings from animal models and human studies, to examine the contributions of the stria vascularis to age-related HL. It provides a brief overview of the structure and function of the stria vascularis and then examines mechanisms contributing to age-related strial dysfunction, including altered ion transport, changes in pigmentation, inflammatory responses, and vascular atrophy. Importantly, this review outlines the contribution of metabolic mechanisms to age-related HL, highlighting areas for future research. It emphasizes the complex interdependence of metabolic and sensorineural mechanisms in the pathology of age-related HL and highlights the importance of animal models in understanding the underlying mechanisms. The comprehensive and mechanistic investigation of all factors contributing to age-related HL, including cochlear metabolic dysfunction, remains crucial to identifying the underlying mechanisms and developing personalized, protective, and restorative treatments.

A critical evaluation of "leakage" at the cochlear blood-stria-barrier and its functional significance

The blood-labyrinth-barrier (BLB) is a semipermeable boundary between the vasculature and three separate fluid spaces of the inner ear, the perilymph, the endolymph and the intrastrial space. An important component of the BLB is the blood-stria-barrier, which shepherds the passage of ions and metabolites from strial capillaries into the intrastrial space. Some investigators have reported increased "leakage" from these capillaries following certain experimental interventions, or in the presence of inflammation or genetic variants. This leakage is generally thought to be harmful to cochlear function, principally by lowering the endocochlear potential (EP). Here, we examine evidence for this dogma. We find that strial capillaries are not exclusive, and that the asserted detrimental influence of strial capillary leakage is often confounded by hair cell damage or intrinsic dysfunction of the stria. The vast majority of previous reports speculate about the influence of strial vascular barrier function on the EP without directly measuring the EP. We argue that strial capillary leakage is common across conditions and species, and does not significantly impact the EP or hearing thresholds, either on evidentiary or theoretical grounds. Instead, strial capillary endothelial cells and pericytes are dynamic and allow permeability of varying degrees in response to specific conditions. We present observations from mice and demonstrate that the mechanisms of strial capillary transport are heterogeneous and inconsistent among inbred strains.

Neuroinflammatory disorders of the brain and inner ear: a systematic review of auditory function in patients with migraine, multiple sclerosis, and neurodegeneration to support the idea of an innovative 'window of discovery'

Background

Hearing can be impaired in many neurological conditions and can even represent a forme fruste of specific disorders. Auditory function can be measured by either subjective or objective tests. Objective tests are more useful in identifying which auditory pathway (superior or inferior) is most affected by disease. The inner ear's perilymphatic fluid communicates with the cerebrospinal fluid (CSF) via the cochlear aqueduct representing a window from which pathological changes in the contents of the CSF due to brain inflammation could, therefore, spread to and cause inflammation in the inner ear, damaging inner hair cells and leading to hearing impairment identifiable on tests of auditory function.

Methods

A systematic review of the literature was performed, searching for papers with case-control studies that analyzed the hearing and migraine function in patients with neuro-inflammatory, neurodegenerative disorders. With data extracted from these papers, the risk of patients with neurological distortion product otoacoustic emission (DPOAE) was then calculated.

Results

Patients with neurological disorders (headache, Parkinson's disease, and multiple sclerosis) had a higher risk of having peripheral auditory deficits when compared to healthy individuals.

Conclusion

Existing data lend credence to the hypothesis that inflammatory mediators transmitted via fluid exchange across this communication window, thereby represents a key pathobiological mechanism capable of culminating in hearing disturbances associated with neuroimmunological and neuroinflammatory disorders of the nervous system.

Case report: Cochlear implantation was effective for progressive bilateral severe hearing loss associated with Kawasaki disease

Sensorineural hearing loss associated with Kawasaki disease has been increasingly reported, but its etiology remains unclear. Most reported cases of sensorineural hearing loss associated with Kawasaki disease have been mild and reversible during acute or subacute phases. However, bilateral severe hearing loss as a complication of Kawasaki disease can cause delays in cognitive and speech development. A 4-year-old Japanese boy treated for Kawasaki disease had right-side moderate and left-side profound sensorineural hearing loss on the 141st day after onset of Kawasaki disease. Despite systemic steroid pulse treatment, hearing loss remained in both sides. After the recurrence of Kawasaki disease, hearing on the right side progressively worsened, meaning there was now severe hearing loss on both sides. Left cochlear implantation performed on the 1065th day after the onset of Kawasaki disease improved the patient's hearing and his ability to communicate. Sensorineural hearing loss associated with Kawasaki disease may progress over a long period and cause bilateral severe hearing loss, although past reports showed occurrence during acute or subacute phases. The clinical course of our patient suggests that intense inflammation caused by Kawasaki disease could be related to prolonged hearing loss. Cochlear implantation seems to be effective for sensorineural hearing loss associated with Kawasaki disease.

Vascular Factors in Patients with Midlife Sensorineural Hearing Loss and the Progression to Mild Cognitive Impairment

Background and Objectives: Midlife hearing loss (HL) has been considered as a major modifiable risk factor for a later-life progression to dementia. Our aim was to detect a link between precocious sensorineural hearing loss (SNHL) and mild cognitive impairment (MCI) and their association to putative risk factors for a common pathology. Materials and methods: In this study, a retrospective case-control study was carried out. A total of 112 patients were enrolled as following: 81 patients with bilateral SNHL and 31 subjects with normal hearing, whose ages ranged from 50 to 65 years. Both groups performed pure tone audiometry, a tinnitus handicap inventory (THI), Mini-Mental State examination (MMSE), and the Montreal Cognitive Assessment (MoCA), Hospital Anxiety and Depression Scale (HADS-A and HADS-D). Results: The mean age was 58 ± 5.2 in SNHL patients and 53.2 ± 4.8 in the control group. The mean pure tone average in the SNHL group was 40.2 ± 18.7 dB HL on the right side and 41.2 ± 17.2 dB HL on the left side, while in the control group it was 12.5 ± 2.8 dB HL on right side and 12.4 ± 3.1 dB HL on left side. About 64% of patients with SNHL exhibited comorbidities, and the most common condition was hypertension. Altered MoCA test scores were significantly related to the pure tone averages in patients with SNHL compared to the control group (p = 0.0004), while the differences in the HADS-A and HADS-D were not significant. Furthermore, a significant correlation was observed in SNHL patients between an altered MoCA test and hypercholesterolemia (p = 0.043). Conclusions: Hearing impairment and screening tests to detect MCI should be considered in the midlife in order to carry out strategies to prevent the progression to dementia. Hypertension and hypercholesterolemia are two risk factors in the development of endothelial dysfunction, oxidative stress, and vascular inflammation, and may represent the common pathology linking the inner ear and brain damage.

Development of a Serum-Free Culture Method for Endothelial Cells of the Stria Vascularis and Their Pro-Inflammatory Secretome Changes Induced by Oxidative Stress

OBJECTIVES

Reactive oxygen species in the stria vascularis (SV) of the cochlea may be involved in the pathogenesis of sensorineural hearing loss. However, the effects of oxidative stress on SV endothelial cells (SV-ECs) remain largely unknown, and no feasible in vitro cell culture model exists for the functional study of SV-ECs.

METHODS

We isolated primary SV-ECs from the SV of neonatal mice. The apoptosis-reducing effects of fibronectin in SV-ECs cultured with serum-free medium were determined using β-galactosidase staining and flow cytometry. SV-ECs incubated in serum-free medium were treated with various H2O2 concentrations to evaluate the effects of H2O2 on their viability. The secretome of SV-ECs treated with or without H2O2 (100 μM or 500 μM) was analyzed using high-resolution mass spectrometry. The function of the SV-EC secretome was evaluated by a macrophage assay.

RESULTS

We successfully isolated and characterized the SV-ECs. Treatment with H2O2 at concentrations up to 500 μM for 2 hours and further incubation with serum-free medium in plates precoated with fibronectin showed no significant effect on apoptosis. Compared to the control SV-ECs, the amount of differential proteins in the secretome of SV-ECs stimulated with 500 μM H2O2 was much higher than in those treated with 100 μM H2O2. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology analyses suggested that the proteins differentially expressed in SV-ECs treated with 500 μM H2O2 were involved in the regulation of multiple signaling pathways and cellular processes. The secretome of H2O2-stimulated SV-ECs exhibited significant pro-inflammatory effects on macrophages.

CONCLUSION

We successfully established an in vitro serum-free culture method, identified the differential proteins released by oxidative stress-induced ECs and their functions, and revealed the pro-inflammatory effects of the secretome of H2O2-stimulated SV-ECs. Therefore, SV-ECs might elicit immunoregulatory effects on bystander cells in the microenvironment of oxidative stress-induced cochlea, especially cochlear macrophages.

Pericytes of Stria Vascularis Are Targets of Cisplatin-Induced Ototoxicity: New Insights into the Molecular Mechanisms Involved in Blood-Labyrinth Barrier Breakdown

The stria vascularis (SV) contributes to cochlear homeostasis and consists of three layers, one of which contains the blood-labyrinthic barrier (BLB), with a large number of bovine cochlear pericytes (BCPs). Cisplatin is a chemotherapeutic drug that can damage the SV and cause hearing loss. In this study, cell viability, proliferation rate, cytotoxicity and reactive oxygen species production were evaluated. The protein content of phospho-extracellular signal-regulated kinases (ERK) 1/2, total ERK 1/2, phospho-cytosolic phospholipase A₂ (cPLA₂), total cPLA₂ and cyclooxygenase 2 (COX-2) and the release of prostaglandin E2 (PGE2) and vascular endothelial growth factor (VEGF) from BCPs were analyzed. Finally, the protective effect of platelet-derived growth factor (PDGF-BB) on BCPs treated with cisplatin was investigated. Cisplatin reduced viability and proliferation, activated ERK 1/2, cPLA₂ and COX-2 expression and increased PGE2 and VEGF release; these effects were reversed by Dexamethasone. The presence of PDGF-BB during the treatment with cisplatin significantly increased the proliferation rate. No studies on cell regeneration in ear tissue evaluated the effect of the PDGF/Dex combination. The aim of this study was to investigate the effects of cisplatin on cochlear pericytes and propose new otoprotective agents aimed at preventing the reduction of their vitality and thus maintaining the BLB structure.

Hearing loss in mice with disruption of auditory epithelial patterning in the cochlea

In the cochlear auditory epithelia, sensory hair and supporting cells are arranged in a checkerboard-like mosaic pattern, which is conserved across a wide range of species. The cell adhesion molecules nectin-1 and nectin-3 are required for this pattern formation. The checkerboard-like pattern is thought to be necessary for auditory function, but has never been examined. Here, we showed the significance of checkerboard-like cellular pattern in the survival and function of sensory hair cells in the cochlear auditory epithelia of nectin-3 knockout (KO) mice. Nectin-3 KO mice showed progressive hearing loss associated with degeneration of aberrantly attached hair cells via apoptosis. Apoptotic hair cell death was due to the disorganization of tight junctions between the hair cells. Our study revealed that the checkerboard-like cellular pattern in the auditory epithelium provides a structural basis for ensuring the survival of cochlear hair cells and hearing function.

[Multifactorial analysis of the degree of hearing loss and outcome in patients with sudden hearing loss]

Objective:To investigate the relationship between the severity and curative effect of hearing loss and clinical indicators in patients with sudden hearing loss （SHL）. Methods:The Spearman correlation coefficient was used to analyze the correlation between the efficacy of SHL and clinical indicators.A total of two hundred and seventy-three patients with SHL were selected and divided into three quantile groups according to the average hearing threshold of the the involved ear frequency of the first pure tone audiometry at admission. Univariate and multivariate ordered logistic regression were used to evaluate the relationship between initial hearing level and clinical indicators of SHL patients. The Spearman correlation coefficient was used to analyze the correlation between efficacy of SHL and clinical indicators. Results:Compared with patients with lower hearing loss （≤50 dB HL），patients with higher hearing loss （>50 dB HL） had higher Neutrophil, Monocyte, Triglycerides, Hemoglobin, Fibrinogen, Glucose, Neutrophil/high-density lipoprotein cholesterol ratio （NHR）, Monocyte/high-density lipoprotein cholesterol ratio, Monocyte/lymphocyte cell ratio, age, dizziness, and lower Platelet/ lymphocyte cell ratio and High-density lipoprotein cholesterol, and poor final hearing threshold.Multivariate logistic regression showed that NHR and age were independent risk factors for initial hearing loss in SHL patients.And the NHR, Neutrophil/lymphocyte cell ratio （NLR）, course of disease, type of hearing curve, and final hearing threshold were significantly negatively correlated with curative effect. Conclusion:SHL patients with higher NHR and NLR values, the longer time from onset to visit, and the more severe hearing loss had worse efficacy.However, SHL patients with higher NHR and age values had greater initial hearing loss,the degree of hearing loss and curative effect are different in SHL patients with different types of hearing threshold curve and age.

Kir5.1 channels: potential role in epilepsy and seizure disorders

Inwardly rectifying potassium (Kir) channels are broadly expressed in many mammalian organ systems, where they contribute to critical physiological functions. However, the importance and function of the Kir5.1 channel (encoded by the KCNJ16 gene) have not been fully recognized. This review focuses on the recent advances in understanding the expression patterns and functional roles of Kir5.1 channels in fundamental physiological systems vital to potassium homeostasis and neurological disorders. Recent studies have described the role of Kir5.1-forming Kir channels in mouse and rat lines with mutations in the Kcnj16 gene. The animal research reveals distinct renal and neurological phenotypes, including pH and electrolyte imbalances, blunted ventilatory responses to hypercapnia/hypoxia, and seizure disorders. Furthermore, it was confirmed that these phenotypes are reminiscent of those in patient cohorts in which mutations in the KCNJ16 gene have also been identified, further suggesting a critical role for Kir5.1 channels in homeostatic/neural systems health and disease. Future studies that focus on the many functional roles of these channels, expanded genetic screening in human patients, and the development of selective small-molecule inhibitors for Kir5.1 channels, will continue to increase our understanding of this unique Kir channel family member.