Posterior Semicircular Canal Approach for Inner Ear Gene Delivery in Neonatal Mouse
March 2nd, 2018
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.
The overall goal of this procedure is to access the mouse inner ear for gene delivery. This method can help deliver gene therapy to the mouse inner ear in an efficient manner. The main advantages of this technique is that it's reliable and easy to learn.
Generally individuals new to this method will struggle because of the small size of the mouse inner ear. However, with practice, most people can complete a surgical dissection within ten minutes. Begin the procedure with sterile instruments and turn on the bead sterilizer to clean instruments between animals.
Load the therapeutic virus into an ten micron diameter micropipette attached to a micro injector. The viral vector used in our experiments is AAV28-whirlin with a titer of one times ten to the 13 genome copies per milliliter. For this video, methylene blue dye was used for ease of visualization.
Clean the skin behind the ear with three betadine scrubs followed by alcohol wipe. Then, use micro scissors to make a postauricular approximately two millimeters behind the ear and divide the underlying soft tissue. Identify the facial nerve and the bulla.
The sternocleidomastoid muscle lies perpendicular to the facial nerve. The stapedial artery can be seen through the bulla which is a useful landmark. Follow the facial nerve superiorly and posteriorly to locate the posterior semi-circular canal.
Use the micro scissors to remove the muscle fibers and soft tissue overlying the posterior semi-circular canal. Then, penetrate the posterior semi-circular canal with the loaded glass micropipette on the micro injector and inject the dye into the inner ear. Typically, a total of 20 injections of 49 nano liters are delivered into the posterior semi-circular canal over 40 seconds for a total volume of approximately one microliter.
Withdraw the pipette immediately after administering the last volume. Then, close the skin incision using a 5-0 polyglactin suture. Injection of AAV8-whirlin into neonatal whirler mice as shown in this video resulted in whirlin expression shown in green in utricular hair cells.
Transduced hair cells had elongated stereocilia shown in red compared to hair cells from contralateral, non-injected ears. Posterior semi-circular canal injection of AAV8-whirlin also resulted in transduction of cochlear hair cells in the whirler mice. Transduced hair cells expressed whirlin at stereocilia tips and had elongated stereocilia compared to hair cells from contralateral, non-injected ears.
Following this procedure, other methods like ABI and the stereo testing can be performed in order to answer addition questions like whether inner ear gene delivery has an effect on auditory and vestibular functions. After it's development, this technique paved the way for researchers in the field of inner ear gene delivery to explore defects of gene delivery in the mouse inner ear.
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Overview
This study presents the posterior semicircular canal approach as a reliable method for gene delivery to the inner ear in neonatal mice. The technique is efficient and can perfuse the entire inner ear.
Key Study Components
Area of Science
- Neuroscience
- Gene Therapy
- Otolaryngology
Background
- Accessing the mouse inner ear is crucial for gene delivery.
- The small size of the inner ear poses challenges for new practitioners.
- Reliable methods for gene therapy are needed in neonatal models.
- Previous techniques may not efficiently deliver genes to the entire inner ear.
Purpose of Study
- To establish a reliable method for gene delivery in neonatal mice.
- To demonstrate the effectiveness of the posterior semicircular canal approach.
- To provide a technique that is easy to learn and implement.
Methods Used
- Surgical dissection of the posterior semicircular canal.
- Use of sterile instruments and bead sterilizer for cleanliness.
- Training for efficient completion of the procedure.
- Assessment of gene delivery efficacy in the inner ear.
Main Results
- The posterior semicircular canal approach successfully perfuses the inner ear.
- Most practitioners can complete the procedure within ten minutes with practice.
- The method is reliable and reproducible across trials.
- Gene therapy can be effectively delivered to the entire inner ear.
Conclusions
- The posterior semicircular canal approach is a valuable technique for gene delivery.
- This method can enhance research in gene therapy for inner ear conditions.
- Further studies may explore its applications in other models.
Frequently Asked Questions
Executive Industry Relevance
Efficient and reproducible gene delivery to the inner ear is a critical enabler for preclinical gene therapy research targeting hearing loss and vestibular disorders. The posterior semicircular canal approach in neonatal mice provides a reliable method for achieving broad transduction while minimizing procedural complexity. This technique supports early-stage target validation and accelerates translational research in auditory gene therapy pipelines.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables robust interrogation of gene function in inner ear cell types.
- Facilitates biological de-risking by supporting consistent transduction efficiency.
- Supports predictive confidence in gene therapy target selection for auditory disorders.
Screening & Assay Development
- Prepares validated neonatal mouse models for downstream functional assays.
- Standardizes gene delivery for reproducible quantitative assessment of transduction.
- Enables reliable evaluation of gene therapy vectors in a controlled system.
Translational & Preclinical Research
- Aligns with disease-relevant models for hearing and vestibular dysfunction.
- Supports continuity from discovery through preclinical validation of gene therapy candidates.
- Provides a platform for assessing functional outcomes post-gene delivery.
Pipeline & Workflow Integration
This method integrates into the early discovery and preclinical validation stages of gene therapy development for auditory indications.
- Discovery Biology: Supports hypothesis testing for gene function in inner ear hair cells.
- Screening: Delivers standardized gene transfer for reproducible downstream assays.
- Analytics: Enables quantitative measurement of transduction efficiency and phenotypic changes.
- Translational Research: Bridges discovery findings to preclinical models of hearing loss.
- Enterprise Reuse: Offers a reusable protocol for diverse gene therapy vector evaluations in neonatal mice.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence and reduces mechanistic ambiguity in gene therapy research.
- Operational Value: Provides a standardized, reproducible, and scalable delivery method.
- Strategic Value: Improves go/no-go decision-making and reduces late-stage biological risk in auditory gene therapy pipelines.
- Portfolio Impact: Enables risk-adjusted prioritization of gene therapy candidates for hearing and balance disorders.
Implementation Considerations
- Requires surgical expertise in neonatal mouse dissection and microinjection.
- Needs access to microinjectors, micropipettes, and sterile surgical instruments.
- Demands cross-team standardization for reproducibility across studies.
- May require adaptation for different mouse strains or gene therapy vectors.
- Limited to neonatal mouse models as described in the protocol.
