whole-neonatal-cochlear-explants-as-an-in-vitro-model

Whole Neonatal Cochlear Explants as an <em>In vitro</em> Model

Untreated hearing loss imposes significant costs on the global healthcare system and impairs individuals' quality of life. Sensorineural hearing loss is ...

University of Basel Hospital

Event-related potentials (ERPs) to task-irrelevant novel sounds have been shown to increase in amplitude with increasing task difficulty and might therefore reflect listening effort. Here we investigated whether this effect is similar in two groups of younger and older listeners with normal hearing.

Effects of age and task difficulty on ERP responses to novel sounds presented during a speech-perception-in-noise test.

Among patients with head and neck cancer comorbid alcohol use disorder is frequent which contributes to higher risk of developing perioperative alcohol withdrawal syndrome/delirium or delirium due to medical conditions. Although guidelines emphasize prevention and treatment of alcohol withdrawal in hospitalized patients, a validated systematic approach for management of these patients is still lacking. Our aim was to formatively evaluate our newly developed systematic approach in view of nurses' adherence to screening patients for regular alcohol consumption and managing their withdrawal symptoms using the Clinical Institute Withdrawal Assessment of Alcohol Scale, Revised.

A systematic nurse-led approach to withdrawal risk screening, prevention and treatment among inpatients with an alcohol use disorder in an ear, nose, throat and jaw surgery department-A formative evaluation.

The process of gentamicin-induced hair cell damage includes the activation of oxidative stress processes. Sestrins, as stress-responsive proteins, protect cells against oxidative stress. Sestrins, particularly Sestrin-2, suppress excessive reactive oxygen species (ROS) accumulation and inhibit mammalian target of rapamycin complex 1 (mTORC1). Thus, we addressed the role of Sestrin-2 in the regulation of sensory hair cell survival after gentamicin exposure. Here, we show that Sestrins were expressed in the inner ear tissues, and Sestrin-2 immunolocalized in sensory hair cells and spiral ganglion (SG). The expression of Sestrin-2 was unchanged, and later downregulated, in gentamicin-treated explants from wild-type mice . Compared with wild-type mice, Sestrin-2 knockout mice exhibited significantly greater hair cell loss in gentamicin-treated cochlear explants. Significant downregulation of phosphorylation of AMP-activated protein kinase alpha (AMPKα) and upregulation of the 70-kDa ribosomal protein S6 kinase (p70S6K) were measured in wild-type cochlear explants exposed to gentamicin compared with their untreated controls. Such regulatory effect was not observed between explants from untreated and gentamicin-treated knockout mice. The gentamicin effect on mTOR signaling was rapamycin-sensitive. Thus, our data provide evidence that Sestrin-2 plays an important role in the protection of hair cells against gentamicin, and the mTOR signaling pathway appears to be modulated by gentamicin during hair cell death.

Sesn2 gene ablation enhances susceptibility to gentamicin-induced hair cell death via modulation of AMPK/mTOR signaling.

Acute sensorineural hearing loss is a dramatic event for the patient. Different pathologies might result in acute sensorineural hearing loss, such as sudden hearing loss, exposure to medications/drugs or loud sound. Current therapeutic approaches include steroids and hyperbaric oxygen in addition to other methods. Research activities of the past have shed light on the molecular mechanisms involved in damage to hair cells, the synapses at the hair cell spiral ganglion junction and the stria vascularis. Molecular events and signaling pathways which underlie damage to these structures have been discovered. Areas covered: This paper summarizes current research efforts involved in investigating the molecular mechanisms involved in acute sensorineural hearing loss. Expert opinion: While progress has been made in unraveling basic mechanisms involved in acute sensorineural hearing loss, it is difficult to translate basic concepts to the clinic. There are often conflicting data in animal and human studies on the effect of a given intervention. There is also a lack of high quality clinical trials (double blind, placebo controlled and high powered). However, this author is confident that research efforts will pay out and that some of these efforts will translate into new therapeutic options for patients with acute hearing loss.

An update on drug design strategies to prevent acquired sensorineural hearing loss.

Brimonidine, an alpha-2 adrenergic receptor (α2-AR) agonist, has neuroprotective effects in the visual system and in spiral ganglion neurons. Auditory hair cells (HCs) express all 3 α2-AR subtypes, but their roles in HCs remain unknown. This study investigated the effects of brimonidine on auditory HCs that were also exposed to gentamicin, which is toxic to HCs. Organ of Corti explants were exposed to gentamicin in the presence or absence of brimonidine, and the α2-AR protein expression levels and Erk1/2 and Akt phosphorylation levels were determined. Brimonidine had a protective effect on auditory HCs against gentamicin-induced toxicity that was blocked by yohimbine. This suggested that the protective effect of brimonidine on HCs was mediated by the α2-AR. None of the treatments altered α2-AR protein expression levels, and brimonidine did not significantly change the activation levels of the Erk1/2 and Akt proteins. These observations indicated that brimonidine, acting directly via α2-AR, protects HCs from gentamicin-induced toxicity. Therefore, brimonidine shows potential for preventing or treating sensorineural hearing loss.

Brimonidine Protects Auditory Hair Cells from in vitro-Induced Toxicity of Gentamicin.

Sesn2/AMPK/mTOR signaling mediates balance between survival and apoptosis in sensory hair cells under stress.

Autophagy is a highly evolutionary conserved quality control defense mechanism within cells, which has also been implicated in cell death processes. In the mammalian inner ear, autophagy has been shown to play a role during early morphogenesis as well as in adult cochlear hair cells exposed to ototoxic insults. Mitophagy, a selective autophagic cell process targeting mitochondria, hasn't been studied in the inner ear so far. On this work, we searched for molecular indicators of mitophagy within House Ear Institute-Organ of Corti-1 (HEI-OC1) cells as well as in the organ of Corti (OC). We first tested for the expression of Pink1/Park2 mRNA in 5-day-old C57BL/6 mice's cochleae using RT-PCR. We focused on the induction of mitophagy in HEI-OC1 cells as well as in the OC and investigated a possible mitophagic potential of the aminoglycoside agent gentamicin. The induction of mitophagy in HEI-OC1 cells was detected by objectivizing the translocation of fluorescence-tagged LC3 to mitochondria using confocal microscopy after a 6-h incubation with a well-described mitochondrial uncoupler and mitophagy-inducing agent: carbonyl cyanide m-chlorophenyl hydrazone (CCCP). Incubation with gentamicin generated no mitochondrial translocation of LC3. Protein levels of COXIV, Atg5/12 and LC3 were evaluated by an immunoblot analysis after a 24-h CCCP treatment as well as gentamicin. We demonstrated mitophagy after CCCP exposure in HEI-OC1 cells by showing a downregulation of COXIV. A downregulation of COXIV could also be visualized in the OC after CCCP. A significant oxygen consumption rate (OCR) changed in cells treated with CCCP as well as significant morphological changes of mitochondria by electron microscopy (EM) strengthen this assumption. Gentamicin exposure generated no impact on OCR or mitochondrial morphological changes by EM. Finally, we demonstrated changes in the expression of Atg12 and LC3 proteins in both the OC and HEI-OC1 cells after CCCP exposure but not after gentamicin. Our data indicate that gentamicin had no impact in the activation of mitophagy-neither in the HEI-OC1 cell line nor in the OC. Therefore, we speculate that mitophagic-independent mechanisms may underly aminoglycoside ototoxicity.

Induction of mitophagy in the HEI-OC1 auditory cell line and activation of the Atg12/LC3 pathway in the organ of Corti.

After cochlear implant (CI) surgery, some patients experience vertigo, dizziness and/or deficits in vestibulo-ocular reflexes. However, little is known about the effect of CI surgery on balance control. Therefore, we examined differences in stance and gait balance control before versus after CI surgery.

Balance Control during Stance and Gait after Cochlear Implant Surgery.

Evaluation of foreign language acquisition at school in cochlear implant patients.

Multicenter Study Investigating Foreign Language Acquisition at School in Children, Adolescents, and Young Adults With Uni- or Bilateral Cochlear Implants in the Swiss German Population.

Telmisartan is an angiotensin II receptor blocker that has pleiotropic effects and protective properties in different cell types. Moreover, telmisartan has also shown partial agonism on the peroxisome proliferator-activated receptor γ (PPAR-γ). Auditory hair cells (HCs) express PPAR-γ, and the protective role of PPAR-γ agonists on HCs has been shown.

Telmisartan Protects Auditory Hair Cells from Gentamicin-Induced Toxicity in vitro.

Hearing loss affects many people worldwide and occurs often as a result of age, ototoxic drugs and/or excessive noise exposure. With a growing number of elderly people, the number of people suffering from hearing loss will also increase in the future. Despite the high number of affected people, for most patients there is no curative therapy for hearing loss and hearing aids or cochlea implants remain the only option. Important treatment approaches for hearing loss include the development of regenerative therapies or the inhibition of cell death/promotion of cell survival pathways. The mammalian target of rapamycin (mTOR) pathway is a central regulator of cell growth, is involved in cell survival, and has been shown to be implicated in many age-related diseases. In the inner ear, mTOR signaling has also started to gain attention recently. In this review, we will emphasize recent discoveries of mTOR signaling in the inner ear and discuss implications for possible treatments for hearing restoration.

mTOR Signaling in the Inner Ear as Potential Target to Treat Hearing Loss.

Hearing loss affects millions of people worldwide. Yet, there are still no curative therapies for sensorineural hearing loss. Frequent causes of sensorineural hearing loss are due to damage or loss of the sensory hair cells, the spiral ganglion neurons, or the synapses between them. Culturing the organ of Corti allows the study of all these structures in an experimental model, which is easy to manipulate. Therefore, the in vitro culture of the neonatal mammalian organ of Corti remains a frequently used experimental system, in which hair cell survival is routinely assessed. However, the analysis of the surviving hair cells is commonly performed via manual counting, which is a time-consuming process and the inter-rater reliability can be an issue. Here, we describe a deep learning approach to quantify hair cell survival in the murine organ of Corti explants. We used StarDist, a publicly available platform and plugin for Fiji (Fiji is just ImageJ), to train and apply our own custom deep learning model. We successfully validated our model in untreated, cisplatin, and gentamicin treated organ of Corti explants. Therefore, deep learning is a valuable approach for quantifying hair cell survival in organ of Corti explants. Moreover, we also demonstrate how the publicly available Fiji plugin StarDist can be efficiently used for this purpose.

Article	Year
Effects of age and task difficulty on ERP responses to novel sounds presented during a speech-perception-in-noise test. Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology\| PubMed ID: 25840528	2016
A systematic nurse-led approach to withdrawal risk screening, prevention and treatment among inpatients with an alcohol use disorder in an ear, nose, throat and jaw surgery department-A form... Applied nursing research : ANR\| PubMed ID: 28096011	2017
Sesn2 gene ablation enhances susceptibility to gentamicin-induced hair cell death via modulation of AMPK/mTOR signaling. Cell death discovery\| PubMed ID: 28580173	2017
An update on drug design strategies to prevent acquired sensorineural hearing loss. Expert opinion on drug discovery\| PubMed ID: 28838250	2017
Brimonidine Protects Auditory Hair Cells from in vitro-Induced Toxicity of Gentamicin. Audiology & neuro-otology\| PubMed ID: 28889125	2017
Sesn2/AMPK/mTOR signaling mediates balance between survival and apoptosis in sensory hair cells under stress. Cell death & disease\| PubMed ID: 28981119	2017
Induction of mitophagy in the HEI-OC1 auditory cell line and activation of the Atg12/LC3 pathway in the organ of Corti. Hearing research\| PubMed ID: 29352609	2018
Balance Control during Stance and Gait after Cochlear Implant Surgery. Audiology & neuro-otology\| PubMed ID: 30300878	2018
Multicenter Study Investigating Foreign Language Acquisition at School in Children, Adolescents, and Young Adults With Uni- or Bilateral Cochlear Implants in the Swiss German Population. Otology & neurotology : official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology\| PubMed ID: 32221106	2020
Telmisartan Protects Auditory Hair Cells from Gentamicin-Induced Toxicity in vitro. Audiology & neuro-otology\| PubMed ID: 32369826	2020
mTOR Signaling in the Inner Ear as Potential Target to Treat Hearing Loss. International journal of molecular sciences\| PubMed ID: 34198685	2021
A deep learning approach to quantify auditory hair cells. Hearing research\| PubMed ID: 34343849	2021

Daniel Bodmer

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