Spiral ganglion neuron quantification in the guinea pig cochlea using Confocal Laser Scanning Microscopy compared to embedding methods

Wrzeszcz, Antonina; Reuter, G.; Nölte, I.; Lenarz, Thomas; Scheper, Verena

doi:10.1016/j.heares.2013.08.002

Cited by 22 publications

(20 citation statements)

References 42 publications

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“…Similar results were shown in the same animal model implanted with dexamethasone-eluting electrodes embedded with a range of drug from 1 to 10% (11) and in cat models, in which no relation between the degree of cochlear inflammation and the ganglion cell density was found (42). The neuronal density of NER and DER groups was similar to neuronal density observed in normal Guinea pigs by Wrzeszcz et al (43), supporting the hypothesis that soft surgery did not damage spiral ganglion neurons. Bas and colleagues demonstrated that electrode insertion trauma causes the loss of synapses and damages of nerve fibers (8), probably because they used a different and invasive surgery approach.…”

Section: Correlation Of Hearing Loss In Animal Studies With Histologisupporting

confidence: 86%

Immune Response After Cochlear Implantation

et al. 2020

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A cochlear implant (CI) is an electronic device that enables hearing recovery in patients with severe to profound hearing loss. Although CIs are a successful treatment for profound hearing impairment, their effectivity may be improved by reducing damages associated with insertion of electrodes in the cochlea, thus preserving residual hearing ability. Inner ear trauma leads to inflammatory reactions altering cochlear homeostasis and reducing post-operative audiological performances and electroacoustic stimulation. Strategies to preserve residual hearing ability led to the development of medicated devices to minimize CI-induced cochlear injury. Dexamethasone-eluting electrodes recently showed positive outcomes. In previous studies by our research group, intratympanic release of dexamethasone for 14 days was able to preserve residual hearing from CI insertion trauma in a Guinea pig model. Long-term effects of dexamethasone-eluting electrodes were therefore evaluated in the same animal model. Seven Guinea pigs were bilaterally implanted with medicated rods and four were implanted with non-eluting ones. Hearing threshold audiograms were acquired prior to implantation and up to 60 days by recording compound action potentials. For each sample, we examined the amount of bone and fibrous connective tissue grown within the scala tympani in the basal turn of the cochlea, the cochleostomy healing, the neuronal density, and the correlation between electrophysiological parameters and histological results. Detection of tumor necrosis factor alpha, interleukin-6, and foreign body giant cells showed that long-term electrode implantation was not associated with an ongoing inflammation. Growth of bone and fibrous connective tissue around rods induced by CI was reduced in the scala tympani by dexamethasone release. For cochleostomy sealing, dexamethasone-treated animals showed less bone tissue growth than negative. Dexamethasone did not affect cell density in the spiral ganglion. Overall, these results support the use of dexamethasone as anti-inflammatory additive for eluting electrodes able to protect the cochlea from CI insertion trauma.

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Section: Correlation Of Hearing Loss In Animal Studies With Histologisupporting

confidence: 86%

Immune Response After Cochlear Implantation

et al. 2020

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“…Whole‐specimen imaging has been used to make three‐dimensional reconstructions of rodent cochleas using digitized optical sections obtained from a variety of fluorescence‐based microscopical techniques, such as orthogonal‐plane fluorescence optical sectioning microscopy (Voie, ; Hofman et al, ), confocal laser scanning microscopy (MacDonald and Rubel, ; Kopecky et al, ; Wrzeszcz et al, ), thin‐sheet laser imaging microscopy (Santi, ) and, more recently, two‐photon excitation fluorescence microscopy which uses near‐infrared excitation wavelengths (Yuan et al, ; Yang et al, ). However, none of these approaches can be used in sedated animals as they require post‐mortem removal of the cochlea from the auditory bulla and rigorous preparatory steps, involving chemical fixation, decalcification, dehydration and clearing.…”

Section: Discussionmentioning

confidence: 99%

Imaging Bioluminescent Exogenous Stem Cells in the Intact Guinea Pig Cochlea

Schomann

Mezzanotte²,

Groot

et al. 2019

The Anatomical Record

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Stem‐cell‐based therapy may be used to replace damaged or lost neurons in the cochlear nerve of patients suffering from severe‐to‐profound sensorineural hearing loss. In order to achieve functional recovery in future clinical trials, knowledge about survival of grafted cells and their differentiation into functional neurons is a prerequisite. This calls for non‐invasive in vivo visualization of cells and long‐term monitoring of their survival and fate after cochlear transplantation. We have investigated if molecular optical imaging enables visualization of exogenous cells in the intact cochlea of guinea pig cadaver heads. Transduced (stem) cells, stably co‐expressing fluorescent (copGFP) and bioluminescent (Luc2) reporter molecules, were injected into the internal auditory meatus or directly into the cochlea through the round window. After injection of the cells into the internal auditory meatus, a bright bioluminescent signal was observed in the cavum conchae of the auricle, indicating that light generated by Luc2 is passing through the tympanic membrane and the external auditory meatus. Similar results were obtained after injection of the cells through the round window membrane, either directly into the scala tympani or in Rosenthal's canal within the modiolus of the basal cochlear turn. Imaging of the auditory bulla demonstrated that the bioluminescent signal passes through the tympanic membrane and crevices in the bony wall of the bulla. After opening the auditory bulla, the bioluminescent signal was emanating from the round window. This is the first study demonstrating that bioluminescence imaging enables visualization of luciferase‐expressing cells injected into the intact guinea pig cochlea. Anat Rec, 303:427–440, 2020. © 2019 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.

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“…SGN density is reported as the average density across the three mid-modiolar sections. Due to the respective sectioning plane, the fourth middle and apical turns (see Wrzeszcz et al, for nomenclature) could not always be analyzed separately and were therefore excluded from the statistical analysis [ 24 ].…”

Section: Methodsmentioning

confidence: 99%

Noise trauma and systemic application of the selective glucocorticoid receptor modulator compound A

Landegger

Honeder

Zhu

et al. 2016

J Negat Results BioMed

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BackgroundSelective glucocorticoid receptor modulators (SEGRMs) comprise a novel class of drugs promising both reduced side effects and similar pharmacological potency relative to glucocorticoids, which presently serve as the only clinical treatment for many otologic disorders. In the first otologic SEGRM experiment in an animal model of noise trauma, we compare the effects of Compound A (a SEGRM) and dexamethasone (potent glucocorticoid).MethodsForty adult guinea pigs received experimental treatment once daily for ten days. The animals were divided into four cohorts based on the treatment received: Compound A (1 mg/kg or 3 mg/kg), dexamethasone (1 mg/kg) as gold standard, or water as negative control. After five applications, animals were exposed to broadband noise (8–16 kHz) at 115 dB for three hours. Hearing thresholds were determined by recording auditory brainstem responses to clicks and noise bursts (1–32 kHz) and were assessed a week prior to and immediately after exposure, as well as on days 1, 3, 7, 14, 21, and 28. Cochleae were prepared as whole-mounts or embedded and sectioned for histological analysis.ResultsRelative to the control treatments, Compound A failed to preserve auditory thresholds post-noise exposure with statistical significance. Histological analyses confirm the physiological result.ConclusionThe present findings suggest that Compound A does not have substantial otoprotective capacities in a noise trauma model.

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Spiral ganglion neuron quantification in the guinea pig cochlea using Confocal Laser Scanning Microscopy compared to embedding methods

Cited by 22 publications

References 42 publications

Immune Response After Cochlear Implantation

Immune Response After Cochlear Implantation

Imaging Bioluminescent Exogenous Stem Cells in the Intact Guinea Pig Cochlea

Noise trauma and systemic application of the selective glucocorticoid receptor modulator compound A

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