Canalostomy As a Surgical Approach to Local Drug Delivery into the Inner Ears of Adult and Neonatal Mice

Summary

Here we describe canalostomy procedure which allows local drug delivery into the inner ears of adult and neonatal mice through the semicircular canal with minimum damage to hearing and vestibular function. This method can be used to inoculate viral vectors, pharmaceuticals, and small molecules into the mouse inner ear.

Abstract

Local delivery of therapeutic drugs into the inner ear is a promising therapy for inner ear diseases. Injection through semicircular canals (canalostomy) has been shown to be a useful approach to local drug delivery into the inner ear. The goal of this article is to describe, in detail, the surgical techniques involved in canalostomy in both adult and neonatal mice. As indicated by fast-green dye and adeno-associated virus serotype 8 with the green fluorescent protein gene, the canalostomy facilitated broad distribution of injected reagents in the cochlea and vestibular end-organs with minimal damage to hearing and vestibular function. The surgery was successfully implemented in both adult and neonatal mice; indeed, multiple surgeries could be performed if required. In conclusion, canalostomy is an effective and safe approach to drug delivery into the inner ears of adult and neonatal mice and may be used to treat human inner ear diseases in the future.

Introduction

Sensorineural hearing loss and vestibular dysfunction affect a substantial number of patients and are closely associated with inner ear disorders. Delivery of therapeutic drugs into the inner ear shows promise for the treatment of inner ear disorders. A systemic or local approach can be used to deliver drugs into the inner ear. Some inner ear diseases are successfully treated with systemic drug administration, such as idiopathic sudden hearing loss, which is commonly treated with systemic steroid¹. In addition, Lentz et al. showed that systemic administration of antisense oligonucleotide was able to improve hearing and balance function....

Protocol

All procedures and animal surgeries were conducted according to the guidelines of the Animal Care and Use Committee of the Capital Medical University of China.

1. Device Preparations

1. To make the injection cannula (Figure 1A), connect polyimide tubing (inner diameter 114.3 µm, outer diameter 139.7 µm, length ~3 cm) to polyethylene tubing (inner diameter 280 µm, outer diameter 640 µm, length ~40 cm). Using superglue, seal the connection with at least three applications. Sterilize the injection cannula with ethylene oxide.
   NOTE: When sealing the tubing, prevent the superglue ....

Results

Fast-green dye was injected into the PSC of adult and neonatal mice to evaluate its immediate distribution in the inner ear. The dye was detected throughout the cochlea, vestibule, and semicircular canals immediately after surgery (Figure 4).

To evaluate the safety and efficiency of canalostomy for inner ear gene delivery, AAV8-GFP was injected into the inner ear of adult and neonatal mice. All anim.......

Discussion

In this study, we showed that drug delivery by canalostomy resulted in widespread distribution of the reagent throughout the cochlea and vestibular end-organs. As an inner ear gene delivery method, canalostomy resulted in GFP expression in the inner ears of adult and neonatal mice with minimum damage to hearing and vestibular function. Furthermore, multiple injections can be easily performed in the same animal.

One of the greatest strengths of canalostomy is that it causes minimal damage to in.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Polymide Tubing	A-M Systems	823400
Polyethylene Tubing	Scientific Commodities Inc.	BB31695-PE/1
10μl Microsyringe	Hamilton Company	80001
Xylazine HCL	Sigma-Aldrich Co. Llc.	X-1251
Operating Miroscope	Carl Zeiss Optical LLC.	Pico
Micro Forceps	Dumont Dumostar	10576
Fast-green Dye	Sigma-Aldrich Co. Llc.	F7252
AAV8-GFP	BioMiao Biological Technology Co. Ltd (Beijing, China)	20161101	Titer: 2×10e12 vg/mL
Streptomycin Sulfate	Sigma-Aldrich Co. Llc.	S9137
Microinjection Pump	Stoelting Co.	789100S
Electric Pad	Pet Fun	11072931136
1 cc Syringe	Mishawa Medical Industries Ltd. (Shanghai, China)	2011-3151258
Ketamine HCL	Gutian Pharmaceutical Co., Ltd. (Fujian, China)	H35020148
Electric Animal Clipper	Codos Electrical Appliances Co., Ltd. (Guangdong, China)	CP-8000
Cotton Pellet	Yatai Healthcare Ltd. (Henan, China)	Yu-2008-1640081
Suture	Shanghai Pudong Jinhuan Medical Products Co., Ltd. (Shanghai, China)	Hu-2013-2650207
Eye Ointment	Beijing Shuangji Pharmaceutical Ltd. (Beijng China)	H11021270