Changes in hearing function and intracochlear morphology after electrode array insertion in minipigs.

BACKGROUND: In temporal bone specimens from long-term cochlear implant users, foreign body response within the cochlea has been demonstrated. However, how hearing changes after implantation and fibrosis progresses within the cochlea is unknown. OBJECTIVES: To investigate the short-term dynamic changes in hearing and cochlear histopathology in minipigs after electrode array insertion. MATERIAL AND METHODS: Twelve minipigs were selected for electrode array insertion (EAI) and the Control. Hearing tests were performed preoperatively and on 0, 7, 14, and 28 day(s) postoperatively, and cochlear histopathology was performed after the hearing tests on 7, 14, and 28 days after surgery. RESULTS: Electrode array insertion had a significant effect for the frequency range tested (1 kHz-20kHz). Exudation was evident one week after electrode array insertion; at four weeks postoperatively, a fibrous sheath formed around the electrode. At each time point, the endolymphatic hydrops was found; no significant changes in the morphology and packing density of the spiral ganglion neurons were observed. CONCLUSIONS AND SIGNIFICANCE: The effect of electrode array insertion on hearing and intracochlear fibrosis was significant. The process of fibrosis and endolymphatic hydrops seemed to not correlate with the degree of hearing loss, nor did it affect spiral ganglion neuron integrity in the 4-week postoperative period.

Genetically modified pigs: Emerging animal models for hereditary hearing loss.

Hereditary hearing loss (HHL), a genetic disorder that impairs auditory function, significantly affects quality of life and incurs substantial economic losses for society. To investigate the underlying causes of HHL and evaluate therapeutic outcomes, appropriate animal models are necessary. Pigs have been extensively used as valuable large animal models in biomedical research. In this review, we highlight the advantages of pig models in terms of ear anatomy, inner ear morphology, and electrophysiological characteristics, as well as recent advancements in the development of distinct genetically modified porcine models of hearing loss. Additionally, we discuss the prospects, challenges, and recommendations regarding the use pig models in HHL research. Overall, this review provides insights and perspectives for future studies on HHL using porcine models.

The Miniature Pig: A Large Animal Model for Cochlear Implant Research.

Cochlear implants (CI) are the most effective method to treat people with severe-to-profound sensorineural hearing loss. Although CIs are used worldwide, no standard model exists for investigating the electrophysiology and histopathology in patients or animal models with a CI or for evaluating new models of electrode arrays. A large animal model with cochlea characteristics similar to those of humans may provide a research and evaluation platform for advanced and modified arrays before their use in humans. To this end, we established standard CI methods with Bama mini-pigs, whose inner ear anatomy is highly similar to that of humans. Arrays designed for human use were implanted into the mini pig cochlea through a round window membrane, and a surgical approach followed that was similar to that used for human CI recipients. Array insertion was followed by evoked compound action potential (ECAP) measurements to evaluate the function of the auditory nerve. This study describes the preparation of the animal, surgical steps, array insertion, and intraoperative electrophysiological measurements. The results indicated that the same CI used for humans could be easily implanted in mini-pigs via a standardized surgical approach and yielded similar electrophysiological outcomes as measured in human CI recipients. Mini-pigs could be a valuable animal model to provide initial evidence of the safety and potential performance of novel electrode arrays and surgical approaches before applying them to human beings.

The Role of Genetic Variants in the Susceptibility of Noise-Induced Hearing Loss.

Noised-induced hearing loss (NIHL) is an acquired, progressive neurological damage caused by exposure to intense noise in various environments including industrial, military and entertaining settings. The prevalence of NIHL is much higher than other occupational injuries in industrialized countries. Recent studies have revealed that genetic factors, together with environmental conditions, also contribute to NIHL. A group of genes which are linked to the susceptibility of NIHL had been uncovered, involving the progression of oxidative stress, potassium ion cycling, cilia structure, heat shock protein 70 (HSP70), DNA damage repair, apoptosis, and some other genes. In this review, we briefly summarized the studies primary in population and some animal researches concerning the susceptible genes of NIHL, intending to give insights into the further exploration of NIHL prevention and individual treatment.

Sox10 Gene Is Required for the Survival of Saccular and Utricular Hair Cells in a Porcine Model.

Pathological changes of the cochlea and hearing loss have been well addressed in Waardenburg syndrome (WS). However, the vestibular organ malformation in WS is still largely unknown. In this study, the differentiation and development of vestibular sensory epithelium and vestibular function caused by SOX10 mutation, a critical gene induces WS, have been studied in minature pig model. Degeneration of vestibular hair cells was found in this Sox10 mutation porcine model. Inner ear phenotype of the SOX10+/R109W miniature pigs showed cochlear abnormalities as well as saccular hypofunction. In the mutant pigs, no prominent dissimilarity was shown in the bone structure of the semicircular canals. However, the saccular membrane was collapsed, and the infusion of stereocilia of the hair cells was observed. There were no dark cells in the utricles in the mutant pigs. The density of the utricular hair cells was also significantly lower in the mutant pigs compared to the wild type. Our study demonstrated that the SOX10 gene and melanocytes play important roles in the vestibular organ development. Sox10 mutation disrupts the KIT-DCT signaling pathway, affects the development of melanocytes, and leads to vestibule morphogenesis.

Involvement of Cholesterol Metabolic Pathways in Recovery from Noise-Induced Hearing Loss.

The objective of this study was to explore the molecular mechanisms of acute noise-induced hearing loss and recovery of steady-state noise-induced hearing loss using miniature pigs. We used miniature pigs exposed to white noise at 120 dB (A) as a model. Auditory brainstem response (ABR) measurements were made before noise exposure, 1 day and 7 days after noise exposure. Proteomic Isobaric Tags for Relative and Absolute Quantification (iTRAQ) was used to observe changes in proteins of the miniature pig inner ear following noise exposure. Western blot and immunofluorescence were performed for further quantitative and qualitative analysis of proteomic changes. The average ABR-click threshold of miniature pigs before noise exposure, 1 day and 7 days after noise exposure, were 39.4 dB SPL, 67.1 dB SPL, and 50.8 dB SPL, respectively. In total, 2,158 proteins were identified using iTRAQ. Both gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) database analyses showed that immune and metabolic pathways were prominently involved during the impairment stage of acute hearing loss. During the recovery stage of acute hearing loss, most differentially expressed proteins were related to cholesterol metabolism. Western blot and immunofluorescence showed accumulation of reactive oxygen species and nuclear translocation of NF-κB (p65) in the hair cells of miniature pig inner ears during the acute hearing loss stage after noise exposure. Nuclear translocation of NF-κB (p65) may be associated with overexpression of downstream inflammatory factors. Apolipoprotein (Apo) A1 and Apo E were significantly upregulated during the recovery stage of hearing loss and may be related to activation of cholesterol metabolic pathways. This is the first study to use proteomics analysis to analyze the molecular mechanisms of acute noise-induced hearing loss and its recovery in a large animal model (miniature pigs). Our results showed that activation of metabolic, inflammatory, and innate immunity pathways may be involved in acute noise-induced hearing loss, while cholesterol metabolic pathways may play an important role in recovery of hearing ability following noise-induced hearing loss.

The characteristics of monosyllable recognition in Mandarin-speaking patients with auditory neuropathy.

Background: A set of Chinese Mandarin monosyllable test lists has been widely used in clinical diagnosis, while the performance of the Mandarin-speaking patients with auditory neuropathy (AN) in the monosyllable tests was still unknown.Objectives: To analyze the characteristics of monosyllable recognition in Mandarin-speaking patients with AN.Materials and methods: Nineteen Mandarin-speaking patients diagnosed with AN were recruited to obtain the performance-intensity (P-I) functions. They were divided into two paired groups according to two conditions: (1) the rising-slope (RS) and the non-rising-slope pattern (NRS) group for the audiogram; or (2) the male and the female group for gender.Results: The performance at 20 and 30 dB SL showed negative correlation with the pure tone-averaged thresholds of 0.5, 1.0, 2.0 and 4.0 kHz (4FA). We found significant differences between the P-I functions of the RS and the NRS group, and surprisingly found that between the male and female as well although there was no difference in 4FA between the paired groups. A notable rollover phenomenon in P-I functions was detected in each group.Conclusions: The monosyllable recognition scores of Mandarin-speaking AN patients showed numerous particular characteristics reflected by P-I functions. Acquiring the complete P-I functions at multiple presentation levels and the rollover index may give us more information about the diagnosis and prognosis.

Transplantation and Tracking of the Human Umbilical Cord Mesenchymal Stem Cell Labeled with Superparamagnetic Iron Oxide in Deaf Pigs.

The purpose of this study was to establish a safe and effective approach to label the human umbilical cord mesenchymal stem cells (UC-MSCs) derived from the Wharton's Jelly with superparamagnetic iron oxide (SPIO) nanoparticles as a cell tracer. The cytotoxicity of the SPIO was screened in vitro by cytochemical experiments. The results showed the new infection protocol of SPIO-Lip2000 mixture had high efficiency and the optimal labeling concentration was a 50 µg/ml SPIO suspension. Transmission electron microscope (TEM) confirmed the distribution of the intracellular SPIO. We transplanted the labeled UC-MSCs into the sensorineural hearing loss (SNHL) minipigs at 1 week after noise exposure. Auditory brainstem response results demonstrated the transplantation of UC-MSCs was an efficient therapy for SNHL. The positive sediments in cochlear blood vessels, the bony wall of scala tympani, and spiral ganglion nerve fibers were found in the stem cell recipients' cochlea. We did not detect iron elements in the inner/outer hair cells' stereocilia, cuticular plate, or pillar cells from the basal to apex turns of the stem cell recipients' cochlea. In addition, TEM found SPIO in the medulla oblongata and the cerebrum in the SNHL minipigs after stem cell transplantation. In conclusion, we established a safe and effective approach to labeled human UC-MSCs derived from Wharton's Jelly by using SPIO nanoparticles as a cell tracer in vitro and in vivo. This protocol showed a wide promising application in stem cell therapy and tracing in vivo for experiments with large mammals. Anat Rec, 303:494-505, 2020. © 2019 American Association for Anatomy.

Degeneration of saccular hair cells caused by MITF gene mutation.

BACKGROUND: Waardenburg syndrome (WS) is the consequence of an inherited autosomal dominant mutation which causes the early degeneration of intermediate cells of cochlear stria vascularis (SV) and profound hearing loss. Patients with WS may also experience primary vestibular symptoms. Most of the current WS studies did not discuss the relationship between WS and abnormal vestibular function. Our study found that a spontaneous mutant pig showed profound hearing loss and depigmentation. MITF-M, a common gene mutation causes type WS which affect the development of the intermediate cell of SV, was then identified for animal modeling. RESULTS: In this study, the degeneration of vestibular hair cells was found in pigs with MITF-M. The morphology of hair cells in vestibular organs of pigs was examined using electron microscopy from embryonic day E70 to postnatal two weeks. Significant hair cell loss in the mutant saccule was found in this study through E95 to P14. Conversely, there was no hair cell loss in either utricle or semi-circular canals. CONCLUSIONS: Our study suggested that MITF-M gene mutation only affects hair cells of the saccule, but has no effect on other vestibular organs. The study also indicated that the survival of cochlear and saccular hair cells was dependent on the potassium release from the cochlear SV, but hair cells of the utricle and semi-circular canals were independent on SV.

Rapid analysis of neomycin in cochlear perilymph of guinea pigs using disposable SPE cartridges and high performance liquid chromatography-tandem mass spectrometry.

Irreversible hearing loss induced by aminoglycoside in human through local or systemic administration route negatively impacts quality of life. The aim of this work was to develop and validate an analytical method suitable for the detection and quantification of neomycin in cochlear perilymph of guinea pig after local application. The SupelMIP SPE column was used for the pre-treatment of matrix. Chromatographic separation was conducted by a reversed phase ODS column (100 × 2.1 mm, 3 µm) at 40 °C in gradient mode with 0.2‰ (v/v) HFBA in water and 0.2‰ (v/v) HFBA in acetonitrile as mobile phase, at a flow rate of 0.30 mL/min, with retention time of 3.50 and 3.62 min for internal standard tobramycin and analyte neomycin, respectively. The MS was performed with positive ionization mode, with data acquisition in Multi Reaction Monitor (MRM) mode. This method was proved to be specific, accurate (97.1-115% of nominal values) and precise (CV% < 15%). Calibration curves for matrix matched standard of neomycin ranged from 1.25 to 200 µg/mL, with LOD and LLOQ of 0.625 and 1.25 µg/mL in blank matrix. The matrix effect was corrected to (-0.1) - 1.33 by adding internal standard. The relative SPE recovery values were ≥98.9% in low, medium and high QC samples. Neomycin in matrix proved to be stable under room temperature - and -20 °C, or under three freeze-thawing cycles, or under processing as well. Finally, the proposed method was successfully applied to a toxicokinetics study of neomycin in perilymph after round window membrane (RWM) administration, which was in accordance with threshold shift of auditory brainstem response (ABR) test related to hearing loss.

Establishing the standard method of cochlear implant in Rongchang pig.

CONCLUSIONS: In this investigation, a large mammal, Rongchang pigs were used to successfully establish a research platform for cochlear implant study on the routine use of it in clinic. OBJECTIVE: The aim of this study was to establish a standard method of cochlear implant in a large mammal-pig. METHODS: Rongchang pigs were selected, then divided into two groups: normal-hearing group (Mitf +/+) and mutation group with hearing loss (Mitf -/-). Cochlear implants were used and ABR and EABR were recorded. The implanted electrodes were observed by X-ray and HE stains. RESULTS: The success with cochlear implant and the best electrode position could be defined in all animals, the coiling of the cochlea reached 1.5-1.75 turns. Immediately after the operation of cochlear implants, the ABR threshold of the operated ear (right) could not be derived for each frequency at 120 dB SPL. Moreover, 7 days after surgery, the low-frequency ABR threshold of the operated ear (right) could be derived partly at 100 dB SPL, but the high-frequency ABR threshold could not be derived at 120 dB SPL. Immediately or 1 week after cochlear implants, the EABR threshold was 90 CL in the Mitf +/+ group. This was obviously lower than the 190 CL in the Mitf -/- group.

Transplantation of human umbilical cord mesenchymal stem cells in cochlea to repair sensorineural hearing.

To examine if transplantation of human umbilical cord mesenchymal stem cells (UMSC) into cochlea can be used to repair sensorineural hearing. Here we transplanted the fifth and sixth generations of UMSCs through the subarachnoid cavity of congenital deaf albino pigs. Auditory brainstem responses (ABR) were measured before and after UMSC transplantation. Cochlear samples were collected at 2 hrs, 3 days, 1, 2, 3, 4 and 8 weeks after transplantation. Immunohistochemistry was used to detect the proliferated cell nuclear antigen (PCNA). The UMSCs were found in different regions of the cochlea, including the stria vascularis, the basal membrane and the spiral ganglions, 3 days to 4 weeks after the transplantation. UMSCs and their DNA were found also in the areas of the brain, the heart, the liver, the kidney and the lung. ABR tests displayed a new waveform in the congenital deaf albino pigs after the UMSCs transplantation. We conclude that human UMSCs injected into the subarachnoid space can migrate into the inner ear, the central nervous system and the periphery organs. The presence of UMSCs in the cochlea maybe associated with changes of ABR waveforms in the congenital deaf albino pigs.

[Study on delivery efficiency and cytotoxicity of Hela cells with mPEG-PLGA-BSA-FITC-NPs nanocarrier].

OBJECTIVE: To construct and obtain ideal protein delivery vectors by researching the delivery efficiency and cytotoxicity to Hela cells using mPEG-PLGA-BSA-FITC-NPs. METHOD: The mPEG-PLGA nanoparticle was obtained through surface modification of PLGA with PEG, and deliver BSA-FITC into Hela cells in vitro. The positive cells were counted by Laser scanning confocal microscopy and the survival rate of Hela cells was calculated by MTT assay at different time points. RESULT: mPEG-PLGA-BSA-FITC-NPs shows the classic nanometer size, and the encapsulation efficiency reached 51. 2%. At the same time, the nanoparticles possess characteristics of slow release. By optimizing the delivery conditions, the highest efficiency of mPEG-PLGA-BSA-FITC-NPs was above 65.2%, and the cellular viability was about 85.7%. CONCLUSION: mPEG-PLGA-BSA-FITC-NPs nanoparticles can successfully carry the target protein into cells as safe and effective as novel delivery materials of protein in vitro, and has shown slow release characteristics. The mPEG-PLGA-BSA-FITC-NPs provide ideal delivery vector for future application in clinical treatment of disease using nano-materials.