Summary

Posterior Semicircular Canal Approach for Inner Ear Gene Delivery in Neonatal Mouse

Published: March 02, 2018
doi:

Summary

In this study, we describe the posterior semicircular canal approach as a reliable method for inner ear gene delivery in neonatal mice. We show that gene delivery through the posterior semicircular canal is able to perfuse the entire inner ear.

Abstract

Inner ear gene therapy offers great promise as a potential treatment for hearing loss and dizziness. 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. In this study, we describe the posterior semicircular canal approach as a viable method for inner ear gene delivery in neonatal mice. We show that gene delivery through the posterior semicircular canal is able to perfuse the entire inner ear. The easy anatomic identification of the posterior semicircular canal, as well as minimal manipulation of the temporal bone required, make this surgical approach an attractive option for inner ear gene delivery.

Introduction

Inner ear gene therapy is a rapidly developing field of investigation. It has been applied in various animals models to combat ototoxicity, noise trauma, and hereditary hearing loss1. Several recent studies have shown functional recovery of hearing and balance functions in mutant mice after inner ear gene therapy delivery2,3,4,5,6,7. One of the key factors in determining the success of inner ear gene therapy is the surgical approach used to access the inner ear. Ideally, the surgical approach would be easy to perform, the anatomic landmarks would be consistent and easy to identify, and the resulting transduction of targeted cell types would be high.

In a recent study, we showed that when viral gene therapy was injected through the posterior semicircular canal of the whirler mutant mouse (a model of hearing loss and vestibular dysfunction), efficient transduction of sensory hair cells was seen in the vestibular organs as well as in the cochlea5. The high efficiency of sensory hair cell transduction resulted in improvement of auditory and vestibular functions in these mutant mice.

In this article, we describe in detail the posterior semicircular canal approach to access the neonatal mouse inner ear.

Protocol

All animal procedures were approved by the Animal Care and Use Committee at the National Institute on Deafness and Other Communication Disorders (NIDCD ASP1378-15). 1. Procedure Setup and Preparation Sterilize all instruments by ethylene oxide in the beginning of the experiment. Between animals, clean instruments using bead sterilization. Load the solution containing viral gene therapy into a micropipette on the micro-injector. The viral vector used in this study was AAV2…

Representative Results

Injection of AAV8-whirlin gene therapy into neonatal whirler mice through the posterior semicircular canal resulted in whirlin expression (green) in utricular hair cells (Figure 2), with the overall infection efficiency of 53.1% (SD 38.1, n = 28)5. Transduced hair cells had elongated stereocilia (red) compared to hair cells from contralateral non-injected ears (5.35 ± 2.11 µm vs. 3.20 ± 0.34 µm, respectively)<sup cl…

Discussion

Several surgical approaches have been described to access rodent inner ears. Cochleostomy and round window approaches are most commonly used to access the cochlea, whereas the posterior semicircular canal and endolymphatic sac approaches are typically used to access the vestibular organs1. In a recent study, we showed that posterior semicircular canal injections of viral gene therapy resulted in high efficiency of hair cell transduction in both the vestibular organs and the cochlea<sup class="xref…

Disclosures

The authors have nothing to disclose.

Acknowledgements

This work was supported by funds from the NIDCD Division of Intramural Research /NIH (DC000082-02 to W.W.C., as well as DC000081 to advanced imaging core). We are grateful for the NIDCD animal facility staff for caring for our animals.

Materials

Operating microscope Zeiss OPMI Pico ENT microscope. Other dissection microscopes would also work.
Micro-forcepts Fine Science Tools 11251-10, 11295-51 #5 and #55 Dumont
Micro-scissors Fine Science Tools 15002-08
Nanoliter2000 microinjector World Precision Instruments
Heating pad Mastex Model 500/600
5-0 vicryl sutures Ethicon
AAV8-whirlin Vector Biolabs
Glass pipette Sutter Instruments B100-75-10 Borosilicate glass

References

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Cite This Article
Isgrig, K., Chien, W. W. Posterior Semicircular Canal Approach for Inner Ear Gene Delivery in Neonatal Mouse. J. Vis. Exp. (133), e56648, doi:10.3791/56648 (2018).

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