Name: A Surgical Procedure for the Administration of Drugs to the Inner Ear in a Non-Human Primate Common Marmoset (Callithrix jacchus) (Video) | JoVE Journal
Uploaded: 2018-02-27T12:30:00.000+00:00
Duration: 6 min 55 s
Description: Learn a surgical method for safe inner ear drug administration in common marmosets (Callithrix jacchus). This technique enables hearing function studies without inducing hearing loss, advancing research toward potential human deafness therapies.

ai_agent_IP

ai_agent

maintenance

instantTrialDurationMinutes

isBiopharma

enableNewMyJoveSectionDesign

educationFeatures

seoMetaApi

ai_copilot_institution_blacklist

ai_chat_institution_blacklist

freeAccessWindow

ssoRoleCapture

scheduledMaintenanceBanner

joveLabsFeatures

disable_autoplay_for_bots

extended_trial_duration

5 minutes

The work is supported by grants to M.F. from the Japanese government MEXT KAKENHI (24592560, 15H04991, and 15K15624) and the Takeda Science Foundation to M.F. and the Jikei University Strategic Prioritizing Research Fund to H.J.O.

All experimental procedures were performed at the Jikei University, Tokyo Japan. Animal handling and experimental procedures were approved by The Institutional Animal Care and Use Committee of The Jikei University (Approval no: 26-060) and performed in accordance with the Institutional guidelines for use of laboratory animals at the Jikei University, which agree with the Guidelines for Proper Conduct of Animal Experiments by the Science Council of Japan (2006). Animal care was conducted in accordance with the recommendations of the Guide for the Care and Use of Laboratory Animals (Institute of Laboratory Animal Resources, 1996).
1. Preoperative Examination
<ol>
	<li>Take a cranial Computed Tomography (CT) scan of animals (common marmosets) in order to facilitate the identification of individual anatomical structures at least one month before surgery.</li>
	<li>Carry out an audiometric test at least one month before surgery. 
	NOTE: Here, we used the ABR to assess hearing status. Briefly, a positive electrode was subcutaneously placed at the vertex and a reference negative electrode at the dorsal base of the stimulated ear. The ground electrode was subcutaneously placed at the dorsal part of the neck.17,18 ABRs were evoked with tone burst (1.0 ms tone burst duration with 0.1 ms rise and fall time). The sound level was then reduced in 10 dB steps from its maximum amplitude. At each sound level, 512 responses were averaged (with stimulus polarity alternated). ABR threshold was defined as the lowest sound pressure level (SPL) at which any wave could be detected.</li>
</ol>
2. Anesthesia
<ol>
	<li>Fast animals from the night before surgery under general anesthesia.</li>
	<li>Administer 4% isoflurane and ambient air at 5 - 6 mL/min with mask-to-face ventilation or in an induction chamber for slow induction (Figure 1A). Confirm that the animal does not respond to painful stimuli, such as the toe pinch.</li>
	<li>Anesthestize common marmosets with intramuscular injection (into the femoral muscle) of a combination of medetomidine (0.04 mg/kg), midazolam (0.4 mg/kg), and butorphanol (0.4 mg/kg).</li>
	<li>Inject ampicillin (0.08 mg/g) subcutaneously 30 min or more&#160;prior to skin incision as a preoperative antibiotic.</li>
	<li>Place the marmoset in the supine position with its head toward the top, and extend the head and neck. Fix the maxilla to the table with a nylon thread, and pull up the tongue to obtain a good view, or use a laryngoscope to visualize the epiglottis and the entry of the larynx alternatively (Figure 1B).</li>
	<li>Insert an endotracheal tube along the laryngeal surface of the epiglottis. 
	NOTE: It is possible to use a 16-gauge intravenous catheter, or 6-French gauge feeding tube, as an endotracheal tube (Figure 1C).</li>
	<li>Check the EtCO2 from the endotracheal tube in order to confirm that it has been properly placed into the trachea. After the tube has been positioned and respiratory gas movement has been checked, fix the endotracheal tube to the marmoset&#39;s face with tape.</li>
	<li>Maintain anesthesia between 1-3% Isoflurane during the operation.</li>
	<li>Monitor the SpO2, EtCO2, body temperature and rectal temperature during operations. Perform all procedures on a heating mat to prevent a reduction in body temperature.</li>
</ol>
3. Preoperative Preparation
<ol>
	<li>Prepare the marmoset in a supine position, and incline the head to a 30 - 45 degree angle to the non-operative side (Figure 2A).</li>
	<li>Shave the post-auricular region of the operative side.</li>
	<li>Disinfect the surgical area with alcohol and povidone iodine, both in the post-auricular region and the external auditory canal.</li>
	<li>Place a surgical drape sheet with a round hole onto the marmoset (Figure 2B).</li>
</ol>
4. Surgical Procedures
<ol>
	<li>Inject 1% of lidocaine hydrochloride (with 1:100,000 epinephrine, 0.1-0.2 mL) subcutaneously into the skin incision site. Make an incision in the postauricular skin with a No.15 round-shaped blade.</li>
	<li>For hemostasis, apply pressure to the bleeding area using a gauze soaked in 1:5,000 diluted epinephrine. Bipolar cauterization is also effective (Figure 2C).</li>
	<li>Open up the soft tissue of the post-auricular region so that auricular cartilage (c) and post-auricular muscle (m) can be recognized. Expose the external auditory canal bone that should be visible deep in the cartilage (Figure 3A).</li>
	<li>To confirm the depth of the tympanic membrane, expose the bony part of the tympanic rim which can be recognized as the adhesion of skin and bone in the deepest part of the posterior ear canal. 
	NOTE: This step allows us to recognize how deep the lateral part of the middle ear cavity is (Figure 3A).</li>
	<li>Peel the post-auricular muscles (sternocleidomastoid muscle, splenius capitis muscle, and posterior belly of digastric muscle) toward the caudal aspect, separated from the temporal bone. Then expose the lateral surface of the temporal bone (asterisk in Figure 3B).</li>
	<li>Make a hole approximately 5 mm behind the external auditory canal with a 1.0 mm diamond bur. (Figure 3C). Use a drill speed of 1,000 - 8,000 rpm depending on the drilling site. 
	NOTE: A slow speed is adequate for delicate manipulation near the semicircular canal or the facial nerve.&#160;Drip the saline in drilling site properly to prevent the thermal injury.</li>
	<li>Enlarge the hole by drilling and confirm the position of the horizontal semicircular canal (HSC), which bulges toward the mastoid cavity (Figure 3D).</li>
	<li>Confirm the position of the facial nerve whose vertical part runs anterior of HSC. Drill and remove all the bone septa, if they exist, to obtain a clear view of the facial recess, which is located at the center of the triangular area between the facial nerve and the chorda tympani.</li>
	<li>Make a small hole by drilling in between the vertical part of the facial nerve and the tympanic rim (asterisk in Figure 4A) with a 0.6 mm diameter diamond bur at 1,000 rpm.</li>
	<li>Move the bur parallel to the posterior canal wall to prevent damage to the facial nerve, which can be seen as a pink line through the thinned bone. Stop the drilling immediately before the nerve is exposed as a white line structure (Figure 4B).</li>
	<li>Ensure the round window niche can be visualized through the hole (Figure 4C). Then, administrate drugs into the niche with a 25-gauge or thinner needle. In order to retain drugs in the round window niche, place a viscous solution on the niche (Figure 4D).</li>
	<li>After confirming that hemostasis is securely controlled, close the layers (epidermal layer and dermal layer) with simple interrupted suture using 6-0 absorbent threads.</li>
	<li>Fix gauze on the surgical wound and affix a bandage.</li>
</ol>
5. Postoperative Care
<ol>
	<li>Administrate atipamezole hydrochloride (0.15 mg/kg) intramuscularly into the femoral muscle to antagonize medetomidine.</li>
	<li>When spontaneous breathing starts, remove the endotracheal tube.</li>
	<li>Maintain the common marmoset in an intensive care unit at 30% O2, 29 &#8451; until anesthesia wears off to complete arousal.</li>
	<li>Confirm that there are no findings suggestive of vestibular dysfunction such as nystagmus, and return the animal to the breeding cage.</li>
</ol>

<ol><li>Liberman, M. C., Kujawa, S. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Cochlear+synaptopathy+in+acquired+sensorineural+hearing+loss%3A+Manifestations+and+mechanisms%5BTitle%5D)+AND+%22Hear+Res%22%5BJournal%5D)">Cochlear synaptopathy in acquired sensorineural hearing loss: Manifestations and mechanisms.</a> Hear Res. 349, 138-147 (2017).</li>
<li>World Health Organization. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=%22Deafness+and+hearing+loss+%28Fact+sheet+N8300%29%22">Deafness and hearing loss (Fact sheet N8300)</a>. , Available from: 
 <a target="_blank" href="http://www.who.int/mediacentre/factsheets/fs300/en/">http://www.who.int/mediacentre/factsheets/fs300/en/</a> (2015).</li>
<li>Thompson, D. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Universal+newborn+hearing+screening%3A+summary+of+evidence%5BTitle%5D)+AND+%22JAMA%22%5BJournal%5D)">Universal newborn hearing screening: summary of evidence.</a> JAMA. 286 (16), 2000-2010 (2001).</li>
<li>Wang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Neural+coding+strategies+in+auditory+cortex%5BTitle%5D)+AND+%22Hear+Res%22%5BJournal%5D)">Neural coding strategies in auditory cortex.</a> Hear Res. 229 (1-2), 81-93 (2007).</li>
<li>Wang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((On+cortical+coding+of+vocal+communication+sounds+in+primates%5BTitle%5D)+AND+%22Proc+Natl+Acad+Sci+U+S+A%22%5BJournal%5D)">On cortical coding of vocal communication sounds in primates.</a> Proc Natl Acad Sci U S A. 97 (22), 11843-11849 (2000).</li>
<li>Bendor, D., Wang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+neuronal+representation+of+pitch+in+primate+auditory+cortex%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">The neuronal representation of pitch in primate auditory cortex.</a> Nature. 436 (7054), 1161-1165 (2005).</li>
<li>Bendor, D., Wang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Neural+coding+of+periodicity+in+marmoset+auditory+cortex%5BTitle%5D)+AND+%22J+Neurophysiol%22%5BJournal%5D)">Neural coding of periodicity in marmoset auditory cortex.</a> J Neurophysiol. 103 (4), 1809-1822 (2010).</li>
<li>Eliades, S. J., Wang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Sensory-motor+interaction+in+the+primate+auditory+cortex+during+self-initiated+vocalizations%5BTitle%5D)+AND+%22J+Neurophysiol%22%5BJournal%5D)">Sensory-motor interaction in the primate auditory cortex during self-initiated vocalizations.</a> J Neurophysiol. 89 (4), 2194-2207 (2003).</li>
<li>Eliades, S. J., Wang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Dynamics+of+auditory-vocal+interaction+in+monkey+auditory+cortex%5BTitle%5D)+AND+%22Cereb+Cortex%22%5BJournal%5D)">Dynamics of auditory-vocal interaction in monkey auditory cortex.</a> Cereb Cortex. 15 (10), 1510-1523 (2005).</li>
<li>Eliades, S. J., Wang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Neural+substrates+of+vocalization+feedback+monitoring+in+primate+auditory+cortex%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">Neural substrates of vocalization feedback monitoring in primate auditory cortex.</a> Nature. 453 (7198), 1102-1106 (2008).</li>
<li>Hosoya, M., Fujioka, M., Ogawa, K., Okano, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Distinct+Expression+Patterns+Of+Causative+Genes+Responsible+For+Hereditary+Progressive+Hearing+Loss+In+Non-Human+Primate+Cochlea%5BTitle%5D)+AND+%22Sci+Rep%22%5BJournal%5D)">Distinct Expression Patterns Of Causative Genes Responsible For Hereditary Progressive Hearing Loss In Non-Human Primate Cochlea.</a> Sci Rep. 6, 22250(2016).</li>
<li>Hosoya, M., Fujioka, M., Kobayashi, R., Okano, H., Ogawa, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Overlapping+expression+of+anion+exchangers+in+the+cochlea+of+a+non-human+primate+suggests+functional+compensation%5BTitle%5D)+AND+%22Neurosci+Res%22%5BJournal%5D)">Overlapping expression of anion exchangers in the cochlea of a non-human primate suggests functional compensation.</a> Neurosci Res. 110, 1-10 (2016).</li>
<li>Sasaki, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Generation+of+transgenic+non-human+primates+with+germline+transmission%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">Generation of transgenic non-human primates with germline transmission.</a> Nature. 459 (7246), 523-527 (2009).</li>
<li>Sato, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Generation+of+a+Nonhuman+Primate+Model+of+Severe+Combined+Immunodeficiency+Using+Highly+Efficient+Genome+Editing%5BTitle%5D)+AND+%22Cell+Stem+Cell%22%5BJournal%5D)">Generation of a Nonhuman Primate Model of Severe Combined Immunodeficiency Using Highly Efficient Genome Editing.</a> Cell Stem Cell. 19 (1), 127-138 (2016).</li>
<li>Sasaki, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Establishment+of+novel+embryonic+stem+cell+lines+derived+from+the+common+marmoset+%28Callithrix+jacchus%29%5BTitle%5D)+AND+%22Stem+Cells%22%5BJournal%5D)">Establishment of novel embryonic stem cell lines derived from the common marmoset (Callithrix jacchus).</a> Stem Cells. 23 (9), 1304-1313 (2005).</li>
<li>Tomioka, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Generating+induced+pluripotent+stem+cells+from+common+marmoset+%28Callithrix+jacchus%29+fetal+liver+cells+using+defined+factors%2C+including+Lin28%5BTitle%5D)+AND+%22Genes+Cells%22%5BJournal%5D)">Generating induced pluripotent stem cells from common marmoset (Callithrix jacchus) fetal liver cells using defined factors, including Lin28.</a> Genes Cells. 15 (9), 959-969 (2010).</li>
<li>Harada, T., Tokuriki, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effects+of+click+intensity+and+frequency+on+the+brain-stem+auditory+evoked+potentials+in+the+common+marmoset+%28Callithrix+jacchus%29%5BTitle%5D)+AND+%22J+Vet+Med+Sci%22%5BJournal%5D)">Effects of click intensity and frequency on the brain-stem auditory evoked potentials in the common marmoset (Callithrix jacchus).</a> J Vet Med Sci. 59 (7), 561-567 (1997).</li>
<li>Harada, T., Tokuriki, M., Tanioka, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Age-related+changes+in+the+brainstem+auditory+evoked+potentials+of+the+marmoset%5BTitle%5D)+AND+%22Hear+Res%22%5BJournal%5D)">Age-related changes in the brainstem auditory evoked potentials of the marmoset.</a> Hear Res. 128 (1-2), 119-124 (1999).</li>
<li>Juhn, S. K., Hunter, B. A., Odland, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Blood-labyrinth+barrier+and+fluid+dynamics+of+the+inner+ear%5BTitle%5D)+AND+%22Int+Tinnitus+J%22%5BJournal%5D)">Blood-labyrinth barrier and fluid dynamics of the inner ear.</a> Int Tinnitus J. 7 (2), 72-83 (2001).</li>
<li>Nakashima, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Disorders+of+cochlear+blood+flow%5BTitle%5D)+AND+%22Brain+Res+Brain+Res+Rev%22%5BJournal%5D)">Disorders of cochlear blood flow.</a> Brain Res Brain Res Rev. 43 (1), 17-28 (2003).</li>
<li>Akil, O., Rouse, S. L., Chan, D. K., Lustig, L. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Surgical+method+for+virally+mediated+gene+delivery+to+the+mouse+inner+ear+through+the+round+window+membrane%5BTitle%5D)+AND+%22J+Vis+Exp%22%5BJournal%5D)">Surgical method for virally mediated gene delivery to the mouse inner ear through the round window membrane.</a> J Vis Exp. (97), (2015).</li>
<li>Jero, J., Tseng, C. J., Mhatre, A. N., Lalwani, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+surgical+approach+appropriate+for+targeted+cochlear+gene+therapy+in+the+mouse%5BTitle%5D)+AND+%22Hear+Res%22%5BJournal%5D)">A surgical approach appropriate for targeted cochlear gene therapy in the mouse.</a> Hear Res. 151 (1-2), 106-114 (2001).</li>
<li>Iizuka, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Noninvasive+in+vivo+delivery+of+transgene+via+adeno-associated+virus+into+supporting+cells+of+the+neonatal+mouse+cochlea%5BTitle%5D)+AND+%22Hum+Gene+Ther%22%5BJournal%5D)">Noninvasive in vivo delivery of transgene via adeno-associated virus into supporting cells of the neonatal mouse cochlea.</a> Hum Gene Ther. 19 (4), 384-390 (2008).</li>
<li>Kilpatrick, L. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Adeno-associated+virus-mediated+gene+delivery+into+the+scala+media+of+the+normal+and+deafened+adult+mouse+ear%5BTitle%5D)+AND+%22Gene+Ther%22%5BJournal%5D)">Adeno-associated virus-mediated gene delivery into the scala media of the normal and deafened adult mouse ear.</a> Gene Ther. 18 (6), 569-578 (2011).</li>
<li>Yamasoba, T., Yagi, M., Roessler, B. J., Miller, J. M., Raphael, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Inner+ear+transgene+expression+after+adenoviral+vector+inoculation+in+the+endolymphatic+sac%5BTitle%5D)+AND+%22Hum+Gene+Ther%22%5BJournal%5D)">Inner ear transgene expression after adenoviral vector inoculation in the endolymphatic sac.</a> Hum Gene Ther. 10 (5), 769-774 (1999).</li>
<li>Kawamoto, K., Oh, S. H., Kanzaki, S., Brown, N., Raphael, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+functional+and+structural+outcome+of+inner+ear+gene+transfer+via+the+vestibular+and+cochlear+fluids+in+mice%5BTitle%5D)+AND+%22Mol+Ther%22%5BJournal%5D)">The functional and structural outcome of inner ear gene transfer via the vestibular and cochlear fluids in mice.</a> Mol Ther. 4 (6), 575-585 (2001).</li>
<li>Praetorius, M., Baker, K., Weich, C. M., Plinkert, P. K., Staecker, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Hearing+preservation+after+inner+ear+gene+therapy%3A+the+effect+of+vector+and+surgical+approach%5BTitle%5D)+AND+%22ORL+J+Otorhinolaryngol+Relat+Spec%22%5BJournal%5D)">Hearing preservation after inner ear gene therapy: the effect of vector and surgical approach.</a> ORL J Otorhinolaryngol Relat Spec. 65 (4), 211-214 (2003).</li>
<li>Nakagawa, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Topical+insulin-like+growth+factor+1+treatment+using+gelatin+hydrogels+for+glucocorticoid-resistant+sudden+sensorineural+hearing+loss%3A+a+prospective+clinical+trial%5BTitle%5D)+AND+%22BMC+Med%22%5BJournal%5D)">Topical insulin-like growth factor 1 treatment using gelatin hydrogels for glucocorticoid-resistant sudden sensorineural hearing loss: a prospective clinical trial.</a> BMC Med. 8, 76(2010).</li>
<li>Piu, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((OTO-104%3A+a+sustained-release+dexamethasone+hydrogel+for+the+treatment+of+otic+disorders%5BTitle%5D)+AND+%22Otol+Neurotol%22%5BJournal%5D)">OTO-104: a sustained-release dexamethasone hydrogel for the treatment of otic disorders.</a> Otol Neurotol. 32 (1), 171-179 (2011).</li>
<li>Plontke, S. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((double+blind%2C+placebo+controlled+trial+on+the+safety+and+efficacy+of+continuous+intratympanic+dexamethasone+delivered+via+a+round+window+catheter+for+severe+to+profound+sudden+idiopathic+sensorineural+hearing+loss+after+failure+of+systemic+therapy%5BTitle%5D)+AND+%22Laryngoscope%22%5BJournal%5D)">double blind, placebo controlled trial on the safety and efficacy of continuous intratympanic dexamethasone delivered via a round window catheter for severe to profound sudden idiopathic sensorineural hearing loss after failure of systemic therapy.</a> Laryngoscope. 119 (2), 359-369 (2009).</li>
<li>Wenzel, G. I., Warnecke, A., Stover, T., Lenarz, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effects+of+extracochlear+gacyclidine+perfusion+on+tinnitus+in+humans%3A+a+case+series%5BTitle%5D)+AND+%22Eur+Arch+Otorhinolaryngol%22%5BJournal%5D)">Effects of extracochlear gacyclidine perfusion on tinnitus in humans: a case series.</a> Eur Arch Otorhinolaryngol. 267 (5), 691-699 (2010).</li>
</ol>

The authors have nothing to disclose.

The volume of cochlear blood flow is extremely small, estimated to be in the order of 1/1,000,000 of the total cardiac output in humans, and access is limited by the presence of the blood-cochlea barrier which separates the inner ear from the general circulation19,20. For these reasons, drug or viral vector administration into the inner ear is favorable, not via systemic administration but rather by direct administration. In mouse and guinea pig experiments, vari...

Sensorineural hearing loss (SNHL) arises predominantly from damage or deficiency in the cochlea. Common causes of SNHL include aging (e.g. presbycusis), genetic defects, exposure to loud noise, infection, and ototoxic drugs1. The World Health Organization (WHO) estimated that over 360 million people, representing 5.3% of the world&#39;s population, suffer from hearing loss2. It is also estimated that 1 in 900 to 1 in 2,500 newborns have moderate, severe, and profound congenital permanent hearing loss, and around one in three adults older than 65 years have some degree of hearing loss3. However, there is no effective clinical treatment of hearing loss for these patients.
Hearing research has long been performed using rodent or guinea pig models, and many approaches, such as gene therapy and regenerative therapy, have been suggested as a new treatment for hearing loss. However, there is a large difference between humans and rodents in terms of the auditory system, and it is very difficult to translate animal models to human applications. The common marmoset (C. jacchus), a New World monkey originating from the Amazon, has become an attractive non-human primate model for various basic research studies for several reasons. First, its anatomy and physiology are more similar to those of the humans rather than rodents. Second, the basic biological information about this species, including diseases, neural networks, behavior, and the genome, is well characterized. Auditory and vocal processing, the cortical coding of periodicity, the representation of pitch, and the auditory-vocal interactions of common marmosets have also been reported4,5,6,7,8,9,10. In recent histological studies, researchers identified distinctive expression patterns of 20 deafness genes and anion exchangers in the cochlea of the common marmoset and found that five genes that are causative of progressive deafness, and three anion exchangers, had different expression patterns from those of rodents11,12. These profiles lead us to believe that the common marmoset is a powerful tool for hearing research.
The most marked attributes of the common marmoset as an experimental animal are as follows:
<ul>
	<li>Easy handling with a small body size compared to some species of Old World monkeys: Adult marmosets weigh 300 - 400 g and are approximately 60 cm in height, which is similar to rats.</li>
	<li>Highly reproductive primate: Marmosets attain sexual maturity at an age of 18 months and are able to bear twice a year and produce 4 to 6 offspring annually.</li>
	<li>Genetic modifications are available: Sasaki E et al. succeeded in creating transgenic13 and knock-out14 primates using marmosets by genetic modifications implicated in neurological disorders (e.g., Parkinson&#39;s disease and Alzheimer&#39;s disease).</li>
	<li>Both embryonic stem (ES) cells and induced pluripotent stem (iPS) cells have been established15,16. Though it is rather difficult to keep the same number of marmosets compared to rodents, the availability of stem cells or iPS cells provides in vitro assays which will reduce the number of in vivo assays required.</li>
</ul>
To facilitate better translational research in the field of deafness and its potential therapy, we established an imaging study protocol using CT and MRI, general anesthesia and hearing tests using auditory brain stem responses (ABRs). These experimental systems may provide us with better opportunities to obtain pre-clinical proof of concept studies which are essential for bridging the gaps between rodent studies and clinical trials. Here, we report a surgical method to administrate drugs to the inner ear of the common marmoset through the round window membrane. To obtain a clear view around the round window, without manipulating the tympanic membrane which might cause a conductive hearing loss, it is useful to approach from the mastoid cavity. Clinically, this approach, referred to as &#34;posterior tympanotomy&#34; is well established and usually used for cochlear implantation and cholesteatoma surgery. We believe that posterior tympanotomy allows us to perform the accurate administration of drugs without inducing hearing loss.

<table><tbody><tr><td>common marmoset</td><td>CLEA Japan</td><td>EDM:C.Marmoset(Jic)</td><td></td></tr><tr><td>isoflurane</td><td>Phizer</td><td></td><td></td></tr><tr><td>medetomidine</td><td>ZENOAQ</td><td></td><td></td></tr><tr><td>midazolam</td><td>astellas</td><td></td><td></td></tr><tr><td>butorphanol</td><td>Meiji Seika</td><td></td><td></td></tr><tr><td>ampicillin</td><td>Meiji Seika</td><td></td><td></td></tr><tr><td>lidocaine hydrochloride</td><td>AstraZeneca</td><td></td><td></td></tr><tr><td>&amp;nbsp;6-0 absorbent thread</td><td>ETHICON</td><td>RD-1</td><td></td></tr><tr><td>atipamezole hydrochloride</td><td>ZENOAQ</td><td></td><td></td></tr><tr><td>phosphate buffered saline</td><td>Wako</td><td>045-29795</td><td></td></tr><tr><td>Surge Wave</td><td>Morita</td><td>TR-900-OR</td><td></td></tr><tr><td>Diamond Bar 006</td><td>Morita</td><td>14070057</td><td></td></tr><tr><td>Diamond Bar 010</td><td>Morita</td><td>14070081</td><td></td></tr><tr><td>intensive care unit</td><td>Menix</td><td>P-100</td><td></td></tr></tbody></table>

a surgical procedure for the administration of drugs to the inner ear in a non-human primate common marmoset (callithrix jacchus)

A Surgical Procedure for the Administration of Drugs to the Inner Ear in a Non-Human Primate Common Marmoset (Callithrix jacchus)

Hearing research has long been facilitated by rodent models, although in some diseases, human symptoms cannot be recapitulated. The common marmoset (Callithrix jacchus) is a small, easy-to-handle New World monkey which has a similar anatomy of the temporal bone, including the middle ear ossicular chains and inner ear to humans, than in comparison with that of rodents. Here, we report a reproducible, safe, and rational surgical approach to the cochlear round window niche for the drug delivery to the inner ear of the common marmoset. We adopted posterior tympanotomy, a procedure used clinically in human surgery, to avoid manipulation of the tympanic membrane that may cause conductive hearing loss. This surgical procedure did not lead to any significant hearing loss. This approach was possible due to the large bulla structure of the common marmoset, although the lateral semicircular canal and vertical portion of the facial nerve should be carefully considered. This surgical method allows us to perform the safe and accurate administration of drugs without hearing loss, which is of great importance in obtaining pre-clinical proof of concept for translational research.

Posterior tympanotomy was performed without any complication such as surgical site infection, bleeding with vascular injury, or vestibular dysfunction, which sometimes occurs with middle ear manipulation. We performed posterior tympanotomy on the right ear of 7-year-old common marmoset and administered 1 µL of phosphate buffered saline to the round window niche. ABRs were measured before and two months after surgery (Figure 5A-B). Waveforms a...

We report a surgical method to administrate drugs to the inner ear of a non-human primate, the common marmoset (Callithrix jacchus), via the round window membrane.

Hearing research has long been facilitated by rodent models, although in some diseases, human symptoms cannot be recapitulated. The common marmoset ...

a-surgical-procedure-for-administration-drugs-to-inner-ear-non-human

Research

JoVE Journal

Medicine

This video showcases canalostomy, a procedure that allows local drug delivery into the inner ear of a mouse through the semicircular canal with minimal damage to hearing and vestibular function. This method enables the inoculation of viral vectors, pharmaceuticals, and small molecules into the mouse's inner ear.

Canalostomy for Local Drug Delivery into the Inner Ear of an Adult Mouse

Two microsurgery approaches for local drug delivery to the inner ear are described here and compared in terms of impact on hearing parameters, cochlear cytoarchitecture and expression of inflammatory markers.

A Comparative Study of Drug Delivery Methods Targeted to the Mouse Inner Ear: Bullostomy Versus Transtympanic Injection

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.

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

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.

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

Animal models of cochlear implants can advance knowledge of the technological bases of treating permanent sensorineural hearing loss with electrical stimulation. This study presents a surgical protocol for acute deafening and cochlear implantation of an electrode array in mice as well as the functional assessment with auditory brainstem response.

Cochlear Implant Surgery and Electrically-evoked Auditory Brainstem Response Recordings in C57BL/6 Mice

We have developed a whole-cortical electrocorticographic array for the common marmoset that continuously covers almost the entire lateral surface of cortex, from the occipital pole to the temporal and frontal poles. This protocol describes a chronic implantation procedure of the array in the epidural space of the marmoset brain.

Chronic Implantation of Whole-cortical Electrocorticographic Array in the Common Marmoset

Here, we demonstrate magnetic resonance (MR)-guided convection enhanced delivery (CED) of viral vectors into the cortex as an efficient and simplified approach for achieving optogenetic expression across large cortical areas in the macaque brain.

Convection Enhanced Delivery of Optogenetic Adeno-associated Viral Vector to the Cortex of Rhesus Macaque Under Guidance of Online MRI Images

This work presents a protocol to perform a stereotaxic, neurosurgical implantation of microelectrode arrays in the common marmoset. This method specifically enables electrophysiological recordings in freely behaving animals but can be easily adapted to any other similar neurosurgical intervention in this species (e.g., cannula for drug administration or electrodes for brain stimulation).

Stereotaxic Surgery for Implantation of Microelectrode Arrays in the Common Marmoset (Callithrix jacchus)

Custom-built micro-drives enable the sub-millimeter targeting of cortical recording sites with linear silicon arrays.

Electrophysiology of Laminar Cortical Activity in the Common Marmoset

To study the evolution of language, comparing brain mechanisms in humans with those in nonhuman primates is important. We developed a method to noninvasively measure the electroencephalography (EEG) of awake animals. It allows us to directly compare EEG data between humans and animals for the long term without harming them.

Electroencephalography Measurements in Awake Marmosets Listening to Conspecific Vocalizations

Learn a surgical method for safe inner ear drug administration in common marmosets (Callithrix jacchus). This technique enables hearing function studies without inducing hearing loss, advancing research toward potential human deafness therapies.

A Surgical Procedure for the Administration of Drugs to the Inner Ear in a Non-Human Primate Common Marmoset (Callithrix jacchus) (Video) | JoVE Journal

A Surgical Procedure for the Administration of Drugs to the Inner Ear in a Non-Human Primate Common Marmoset (Callithrix jacchus)

Explore More Videos