The temporal bone microdissection of miniature pigs as a useful large animal model for otologic research

Investigation of inner ear drug delivery with a cochlear catheter in piglets as a representative model for human cochlear pharmacokinetics

Hearing impairment is the most common sensory disorder in humans, and yet hardly any medications are licensed for the treatment of inner ear pathologies. Intricate pharmacokinetic examinations to better understand drug distribution within this complex organ could facilitate the development of novel therapeutics. For such translational research projects, animal models are indispensable, but differences in inner ear dimensions and other anatomical features complicate the transfer of experimental results to the clinic. The gap between rodents and humans may be bridged using larger animal models such as non-human primates. However, their use is challenging and impeded by administrative, regulatory, and financial hurdles. Other large animal models with more human-like inner ear dimensions are scarce. In this study, we analyzed the inner ears of piglets as a potential representative model for the human inner ear and established a surgical approach for intracochlear drug application and subsequent apical sampling. Further, controlled intracochlear delivery of fluorescein isothiocyanate-dextran (FITC-d) was carried out after the insertion of a novel, clinically applicable CE-marked cochlear catheter through the round window membrane. Two, six, and 24 hours after a single injection with this device, the intracochlear FITC-d distribution was determined in sequential perilymph samples. The fluorometrically assessed concentrations two hours after injection were compared to the FITC-d content in control groups, which either had been injected with a simple needle puncture through the round window membrane or the cochlear catheter in combination with a stapes vent hole. Our findings demonstrate not only significantly increased apical FITC-d concentrations when using the cochlear catheter but also higher total concentrations in all perilymph samples. Additionally, the concentration decreased after six and 24 hours and showed a more homogenous distribution compared to shorter observation times.

A Window of Opportunity: Perilymph Sampling from the Round Window Membrane Can Advance Inner Ear Diagnostics and Therapeutics

In the clinical setting, the pathophysiology of sensorineural hearing loss is poorly defined and there are currently no diagnostic tests available to differentiate between subtypes. This often leaves patients with generalized treatment options such as steroids, hearing aids, or cochlear implantation. The gold standard for localizing disease is direct biopsy or imaging of the affected tissue; however, the inaccessibility and fragility of the cochlea make these techniques difficult. Thus, the establishment of an indirect biopsy, a sampling of inner fluids, is needed to advance inner ear diagnostics and allow for the development of novel therapeutics for inner ear disease. A promising source is perilymph, an inner ear liquid that bathes multiple structures critical to sound transduction. Intraoperative perilymph sampling via the round window membrane of the cochlea has been successfully used to profile the proteome, metabolome, and transcriptome of the inner ear and is a potential source of biomarker discovery. Despite its potential to provide insight into inner ear pathologies, human perilymph sampling continues to be controversial and is currently performed only in conjunction with a planned procedure where the inner ear is opened. Here, we review the safety of procedures in which the inner ear is opened, highlight studies where perilymph analysis has advanced our knowledge of inner ear diseases, and finally propose that perilymph sampling could be done as a stand-alone procedure, thereby advancing our ability to accurately classify sensorineural hearing loss.

Viewing the current situation of pig model application in China's medical field from the application and funding of NSFC

Background

The National Natural Science Foundation of China (NSFC) is an important part of China’s innovation system. In the last decade, the pig has become more and more widely used in the field of medical science, especially in otology research.

Objective

By analyzing and summarizing the funding information over recent years, we intend to identify the characteristics and trends of funding for research using pig models and provide references for future development.

Material and methods

This is a comprehensive analysis of features in funding for research projects involving pig models by the NSFC in the past 10 years, with a focus on projects in the field of otolaryngology/head and neck surgery.

Results

Both the number and amount of funding provided by the NSFC for research involving pig models are on the rise with each passing year. Researchers at the PLA General Hospital have completed a number of studies using miniature pigs in cochlear morphology, electrophysiology, cochlear implantation, cochlear transcription analysis, gene therapy, inner ear disease modeling and Eustachian tube pathology modeling.

Conclusion

Pigs as an ideal large mammal model are well suited in the current national basic research strategy in China, and can help further strengthen China’s leading position in basic research in the world.

Canalostomy is an ideal surgery route for inner ear gene delivery in big animal model

Background: Inner gene therapy offers great promises as a potential treatment for hearing loss. Aims/objectives: One of the critical determinants of the success of inner ear gene therapy is to find a delivery method which results in consistent transduction efficiency of targeted cell types while minimizing hearing loss. Material and methods: Surgery was performed only in the right ear of each Bama miniature pig, and the left ear served as a control. The gene delivery to inner ear via round window membrane (RWM) and posterior semicircular canal (PSC) approach was performed with the viral vector AAV1-CMV-GFP. Results: The gene delivery through RWM and the PSC (canalostomy) is able to perfuse the inner ear. Conclusions and significance: The easy anatomic identification of the PSC, as to RWM, as well as minimal manipulation of the temporal bone required, make this surgical approach an attractive option for inner ear gene delivery in big animal model.

A miR-511-binding site SNP in the 3'UTR of IGF-1 gene is associated with proliferation and apoptosis of PK-15 cells

Insulin-like growth factor-1 (IGF-1) is a functional candidate gene for pig growth and development due to its crucial role in the growth axis of growth hormone-IGF-1. Considering that the 3' untranslated region (3'UTR) of gene may affect its expression, we analyzed the effect of a single-nucleotide polymorphism (SNP) (rs34142920, c.674C > T) on gene expression, cell proliferation, and apoptosis and the possible related molecular mechanisms in PK-15 cells. The SNP was found in the 3'UTR of IGF-1 in Bama Xiang pig in previous investigations. Results showed that the SNP was located at the target site binding to microRNA (miR-511). The 3'UTR of IGF-1 gene with C allele significantly downregulated the expression of IGF-1 gene compared with that of the gene with T allele by luciferase assay. miR-511 was transfected into porcine kidney cell line (PK-15 cells) to reveal its effects on cells and whether or not it targets IGF-1. The expression levels of IGF-1 at mRNA and protein levels were remarkably downregulated. miR-511 significantly inhibited cell proliferation and promoted cell apoptosis by downregulating the phosphorylation level of AKT and ERK1/2. This finding confirmed that miR-511 inhibits proliferation and promotes apoptosis by downregulating the IGF-1 in PK-15 cells.

High Resolution Computed Tomography Atlas of the Porcine Temporal Bone and Skull Base: Anatomical Correlates for Traumatic Brain Injury Research

Brain injuries are a significant cause of morbidity and mortality worldwide. Auditory and vestibular dysfunction may occur following trauma to the temporal bone (TB), including the lateral skull base. The porcine model is a commonly used large animal model for investigating brain injury. Reports detailing porcine TB anatomy based on high resolution computed tomography (HRCT) imaging, however, are limited. Herein, we employ HRCT to evaluate and describe the bony anatomy of the porcine TB and lateral skull base. High-resolution multi-detector and cone beam CT were used to image porcine TBs (n = 16). TBs were analyzed for major anatomical structures and compared to human species. Porcine temporal bone anatomy was readily identifiable by HRCT. Although some variability exists, the ossicular chain, vestibule, cochlea, course of the facial nerve, and skull base are similar to those of humans. Major differences included position of the external auditory canal and mastoid, as well as presence of the petrous carotid canal. Study findings may serve as an atlas to evaluate the porcine middle and inner ear, as well as lateral skull base injuries for future porcine brain injury models or other studies that require CT-based analysis.

Establishment of a Large Animal Model for Eustachian Tube Functional Study in Miniature Pigs

This study was performed to investigate whether miniature pigs are a suitable animal model for studies of the Eustachian tube (ET). Sixteen Chinese experimental miniature pigs were used in this investigation. Ten animals were used for anatomical and morphometric analyses to obtain qualitative and quantitative information regarding the ET. Three animals were used for histological analysis to determine the fine structure of ET cross-sections. Three animals were used to investigate the feasibility of balloon dilation of the Eustachian tube (BDET). The anatomical study indicated that the pharyngeal orifice and tympanic orifice of the miniature pig ET are located at the posterior end of the nasal lateral wall and anterior wall of the middle ear cavity, respectively. The cartilaginous tube was seen to pass through the whole length of the ET, the length of the cartilaginous part of the ET and the diameter of the isthmus were similar between humans and miniature pigs. The inclination of the ET in miniature pigs was larger than that in humans. The gross histology seemed to be slightly different between miniature pig and human, but the fine structures were essentially the same in both species. BDET experiments verified that the miniature pig model is suitable as a model for clinical operations. The miniature pig ET corresponds very well to that of humans. In addition, the miniature pig ET is suitable as a model for clinical operations. Therefore, the miniature pig is a valid animal model for ET study. Anat Rec, 302:1024-1038, 2019. © 2019 Wiley Periodicals, Inc.

The morphological and functional development of the stria vascularis in miniature pigs

The purpose of this study was to examine the morphological and functional development of the lateral wall of the scala media of the cochlea in miniature pigs; light and transmission electron microscopy and electrophysiology were used for this purpose. We showed that the lateral wall of the scala media of the cochlea appears at embryonic Day 21 (E21) when the cochlear duct begins to form. From E28 to E49, the lateral wall can be distinguished according to its position along the cochlea. At E56, cells in the lateral wall begin to differentiate into three different types. At E70, three cell types, marginal, intermediate and basal, can be clearly distinguished. At E91, the stria vascularis is adult-like and the organ of Corti is also morphologically mature. The average endocochlear potential measured from the second turn of the cochlea (at E98, postnatal Day 1 (P1), P13 and P30) was 71.4±2.5 (n=7), 78.8±1.5 (n=10), 77.3±2.3 (n=10) and 78.0±2.1 mV (n=10), respectively. Our results suggest that in miniature pigs the stria vascularis develops during the embryonic period, concurrent with maturation of the organ of Corti. The magnitude of the endocochlear potential reached its mature level when the stria vascularis was morphologically adult-like at E98. These findings provide a morphological and functional basis for future animal studies using the miniature pig model concerning the pathogenesis of various inner-ear diseases.

Transcription analysis of cochlear development in minipigs

CONCLUSIONS

The critical stage for cochlear gene regulation in the embryo is E49-E56. These data provide a valuable resource to help elucidate gene regulation in cochlear development and will benefit ear-related studies, especially those that focus on gene and stem cell therapies in hearing loss.

OBJECTIVES

To investigate gene regulation in cochlear development and provide reference information for ear-related research.

METHODS

Total RNA extraction from the Bama miniature pig cochlea was performed at five time points that covered most of the cochlea development process (E42, E49, E56, E91, P13). Transcriptome sequencing was performed by Illumina HiSeq 2500. Transcriptome data were mapped to the genome using TopHat2. Gene expression was quantified using the Cuffquant and Cuffnorm modules. GO and KEGG pathway-enrichment analysis were in progress about the differentially expressed genes (DEGs) by Perl programs.

RESULTS

Sequencing of 1778643560000 paired reads revealed 35.9 G of data, and 19,432 expression genes were detected. The ratio of these pairs to the Ensembl genome database was approximately 71% in all samples. The stages E49-E91 and, especially, E49-E56 included the most rapid changes in gene regulation and differentiation for the cochlea. The stem cell characteristics of neural stem cells decreased most rapidly during this period.

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.