Utilizing Single Cell RNA-Sequencing to Implicate Cell Types and Therapeutic Targets for SSNHL in the Adult Cochlea

Advance and Application of Single-cell Transcriptomics in Auditory Research

Hearing loss and deafness, as a worldwide disability disease, have been troubling human beings. However, the auditory organ of the inner ear is highly heterogeneous and has a very limited number of cells, which are largely uncharacterized in depth. Recently, with the development and utilization of single-cell RNA sequencing (scRNA-seq), researchers have been able to unveil the complex and sophisticated biological mechanisms of various types of cells in the auditory organ at the single-cell level and address the challenges of cellular heterogeneity that are not resolved through by conventional bulk RNA sequencing (bulk RNA-seq). Herein, we reviewed the application of scRNA-seq technology in auditory research, with the aim of providing a reference for the development of auditory organs, the pathogenesis of hearing loss, and regenerative therapy. Prospects about spatial transcriptomic scRNA-seq, single-cell based genome, and Live-seq technology will also be discussed.

Blood tests as biomarkers for the diagnosis and prognosis of sudden sensorineural hearing loss in adults: a systematic review

OBJECTIVE

Sudden sensorineural hearing loss is considered idiopathic in up to 90 per cent of cases. This study explored the role of blood tests as biomarkers for the diagnosis and prognosis of sudden sensorineural hearing loss.

METHOD

Two researchers filtered 34 papers into the final review. This review was pre-registered on the Prospero database and conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines.

RESULTS

Raised inflammatory markers are almost universal in sudden sensorineural hearing loss, suggesting an inflammatory or autoimmune process. The most useful biomarkers are neutrophil-lymphocyte ratio, platelet-lymphocyte ratio and fibrinogen level. Focused investigations should be deployed on a case-by-case basis to identify underlying metabolic, infective and autoimmune conditions.

CONCLUSION

A full blood count and coagulation screen (fibrinogen) is recommended in all cases of sudden sensorineural hearing loss. These are inexpensive, accessible and offer as much diagnostic and prognostic information as any other biomarker. There is emerging evidence regarding specific biomarkers for sudden sensorineural hearing loss prognosis, with heat shock protein-70, anti-endothelial cell antibody and prestin demonstrating potential; investigation of their validity through prospective, controlled research is recommended.

Prognostic changes after sudden deafness in patients with inner ear malformations characterized by LSCC: a retrospective study

Introduction

This study aimed to investigate the clinical features and prognosis of sudden sensorineural hearing loss in patients with lateral semicircular canal (LSCC) malformation.

Methods

This study enrolled patients with LSCC malformation and sudden sensorineural hearing loss (SSNHL) who were admitted to Shandong ENT Hospital between 2020 and 2022. We collected and analyzed data on examinations of audiology, vestibular function, and imaging records of patients and summarized the clinical characteristics and prognosis of these patients.

Results

Fourteen patients were enrolled. Patients with LSCC malformation was noted in 0.42% of all SSNHL cases during the same period. One patients had bilateral SSNHL and the rest had unilateral SSNHL. Of them, eight and six patients had unilateral and bilateral LSCC malformations, respectively. Flat hearing loss was noted in 12 ears (80.0%) and severe or profound hearing loss was noted in 10 ears (66.7%). After treatment, the total efficacy rate of SSNHL with LSCC malformation was 40.0%. Vestibular function was abnormal in all patients, but only five patients (35.7%) had dizziness. There were statistically significant differences in the vestibular functions between patients with LSCC malformation and matched patients without the malformation hospitalized during the same period (p < 0.05).

Conclusion

Patients with SSNHL and LSCC malformation had flat-type and severe hearing loss and worse disease prognosis compared to those with SSNHL without LSCC malformation. Vestibular function is more likely to be abnormal; however, there was no significant difference in vestibular symptoms between patients with and without LSCC malformation. LSCC is a risk factor for the prognosis of SSNHL.

In Silico Localization of Perilymph Proteins Enriched in Meńier̀e Disease Using Mammalian Cochlear Single-cell Transcriptomics

Hypothesis

Proteins enriched in the perilymph proteome of Meńier̀e disease (MD) patients may identify affected cell types. Utilizing single-cell transcriptome datasets from the mammalian cochlea, we hypothesize that these enriched perilymph proteins can be localized to specific cochlear cell types.

Background

The limited understanding of human inner ear pathologies and their associated biomolecular variations hinder efforts to develop disease-specific diagnostics and therapeutics. Perilymph sampling and analysis is now enabling further characterization of the cochlear microenvironment. Recently, enriched inner ear protein expression has been demonstrated in patients with MD compared to patients with other inner ear diseases. Localizing expression of these proteins to cochlear cell types can further our knowledge of potential disease pathways and subsequent development of targeted therapeutics.

Methods

We compiled previously published data regarding differential perilymph proteome profiles amongst patients with MD, otosclerosis, enlarged vestibular aqueduct, sudden hearing loss, and hearing loss of undefined etiology (controls). Enriched proteins in MD were cross-referenced against published single-cell/single-nucleus RNA-sequencing datasets to localize gene expression to specific cochlear cell types.

Results

In silico analysis of single-cell transcriptomic datasets demonstrates enrichment of a unique group of perilymph proteins associated with MD in a variety of intracochlear cells, and some exogeneous hematologic and immune effector cells. This suggests that these cell types may play an important role in the pathology associated with late MD, suggesting potential future areas of investigation for MD pathophysiology and treatment.

Conclusions

Perilymph proteins enriched in MD are expressed by specific cochlear cell types based on in silico localization, potentially facilitating development of disease-specific diagnostic markers and therapeutics.

The role of the stria vascularis in neglected otologic disease

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

Bioinformatic Analysis of the Perilymph Proteome to Generate a Human Protein Atlas

The high complexity of the cellular architecture of the human inner ear and the inaccessibility for tissue biopsy hampers cellular and molecular analysis of inner ear disease. Sampling and analysis of perilymph may present an opportunity for improved diagnostics and understanding of human inner ear pathology. Analysis of the perilymph proteome from patients undergoing cochlear implantation was carried out revealing a multitude of proteins and patterns of protein composition that may enable characterisation of patients into subgroups. Based on existing data and databases, single proteins that are not present in the blood circulation were related to cells within the cochlea to allow prediction of which cells contribute to the individual perilymph proteome of the patients. Based on the results, we propose a human atlas of the cochlea. Finally, druggable targets within the perilymph proteome were identified. Understanding and modulating the human perilymph proteome will enable novel avenues to improve diagnosis and treatment of inner ear diseases.

In silico Single-Cell Analysis of Steroid-Responsive Gene Targets in the Mammalian Cochlea

Background

Treatment of many types of hearing instability in humans, including sudden sensorineural hearing loss, Meniere's disease, and autoimmune inner ear disease, rely heavily on the utilization of corticosteroids delivered both by oral and transtympanic routes. Despite this use, there is heterogeneity in the response to treatment with corticosteroids in humans with these diseases. The mechanisms by which corticosteroids exert their effect and the cell types in which they exert their effects in the inner ear remain poorly characterized. In this study, we localize steroid-responsive genes to cochlear cell types using previously published transcriptome datasets from the mammalian cochlea.

Methods

Steroid-responsive genes were localized to specific cochlear cell types using existing transcriptome datasets from wild-type mammalian cochlea exposed to systemic and transtympanic steroids, as well as previously published single-cell and single-nucleus RNA-sequencing datasets from the mammalian cochlea. Gene ontology (GO) analysis of differentially expressed genes (DEGs) was performed using PANTHER to investigate cellular processes implicated in transtympanic vs. systemic steroid action in the cochlea.

Results

Steroid-responsive genes were localized to specific cell types and regions in the cochlea including the stria vascularis, organ of Corti, and spiral ganglion neurons (SGN). Analyses demonstrate differential prevalence of steroid-responsive genes. GO analysis demonstrated steroid-responsive DEGs in the SGN to be associated with angiogenesis, apoptosis, and cytokine-mediated anti-inflammatory pathways.

Conclusions

Single-cell and single-nucleus transcriptome datasets localize steroid-responsive genes to specific regions in the cochlea. Further study of these regionally-specific steroid-responsive genes may provide insight into the mechanisms of and clinical response to corticosteroids in diseases of hearing instability.