This work was supported in part by the NIDCD Grants No. 1K08DC020780 and 5T32DC000027-33, and the Rubenstein Hearing Research Fund.

All animal procedures were approved by the Institutional Animal Care and Use Committee (GP18M226). Hartley albino guinea pigs (both male and female, weighing 500-700 g) were used in the present study.
1. Procedure setup and preparation
<ol>
	<li>Sterilize all instruments with ethylene oxide before beginning the experiment.</li>
	<li>Euthanize the animals following the institutionally approved protocol. 
	NOTE: In the current study, a non-precharged chamber was employed ...

Guinea Pig Round Window Membrane Explantation

<ol>
	<li>Duan, M. I., Zhi-qiang, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Permeability+of+round+window+membrane+and+its+role+for+drug+delivery:+our+own+findings+and+literature+review.">Permeability of round window membrane and its role for drug delivery: our own findings and literature review.</a> J Otol. 4 (1), 34-43 (2009).</li><li>Kelso, C. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microperforations+significantly+enhance+diffusion+across+round+window+membrane.">Microperforations significantly enhance diffusion across round window membrane.</a> Otol Neurotol. 36 (4), 694-700 (2015).</li><li>Salt, A. N., Plontke, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pharmacokinetic+principles+in+the+inner+ear:+Influence+of+drug+properties+on+intratympanic+applications.">Pharmacokinetic principles in the inner ear: Influence of drug properties on intratympanic applications.</a> Hear Res. 368, 28-40 (2018).</li><li>Szeto, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inner+ear+delivery:+Challenges+and+opportunities.">Inner ear delivery: Challenges and opportunities.</a> Laryngoscope Investig Otolaryngol. 5 (1), 122-131 (2020).</li><li>Carpenter, A. M., Muchow, D., Goycoolea, M. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrastructural+studies+of+the+human+round+window+membrane.">Ultrastructural studies of the human round window membrane.</a> Arch Otolaryngol Head Neck Surg. 115 (5), 585-590 (1989).</li><li>Forouzandeh, F., Borkholder, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microtechnologies+for+inner+ear+drug+delivery.">Microtechnologies for inner ear drug delivery.</a> Curr Opin Otolaryngol Head Neck Surg. 28 (5), 323-328 (2020).</li><li>Leong, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microneedles+facilitate+small-volume+intracochlear+delivery+without+physiologic+injury+in+guinea+pigs.">Microneedles facilitate small-volume intracochlear delivery without physiologic injury in guinea pigs.</a> Otol Neurotol. 44 (5), 513-519 (2023).</li><li>Singh, R., Birru, B., Veit, J. G. S., Arrigali, E. M., Serban, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+characterization+of+an+in+vitro+round+window+membrane+model+for+drug+permeability+evaluations.">Development and characterization of an in vitro round window membrane model for drug permeability evaluations.</a> Pharmaceuticals (Basel). 15 (9), 1105 (2022).</li><li>Du, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetic+targeted+delivery+of+dexamethasone+acetate+across+the+round+window+membrane+in+guinea+pigs.">Magnetic targeted delivery of dexamethasone acetate across the round window membrane in guinea pigs.</a> Otol Neurotol. 34 (1), 41-47 (2013).</li><li>Kopke, R. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetic+nanoparticles:+inner+ear+targeted+molecule+delivery+and+middle+ear+implant.">Magnetic nanoparticles: inner ear targeted molecule delivery and middle ear implant.</a> Audiol Neurootol. 11 (2), 123-133 (2006).</li><li>AVMA. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=AVMA+Guidelines+for+the+Euthanasia+of+Animals:+2020+Edition.">AVMA Guidelines for the Euthanasia of Animals: 2020 Edition.</a> AVMA. , (2020).</li><li>Goksu, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anatomy+of+the+guinea+pig+temporal+bone.">Anatomy of the guinea pig temporal bone.</a> Ann Otolaryngol. 101 (8), 699-704 (1992).</li><li>Wysocki, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Topographical+anatomy+of+the+guinea+pig+temporal+bone.">Topographical anatomy of the guinea pig temporal bone.</a> Hear Res. 199 (1), 103-110 (2005).</li><li>Veit, J. G. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+evaluation+of+the+drug+permeability+properties+of+human+cadaveric+in+situ+tympanic+and+round+window+membranes.">An evaluation of the drug permeability properties of human cadaveric in situ tympanic and round window membranes.</a> Pharmaceuticals (Basel). 15 (9), 1037 (2022).</li><li>Kansara, V., Mitra, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+an+ex+vivo+model+implication+for+carrier-mediated+retinal+drug+delivery).">Evaluation of an ex vivo model implication for carrier-mediated retinal drug delivery).</a> Curr Eye Res. 31 (5), 415-426 (2006).</li><li>Lundman, L., Bagger-Sj&#246;b&#228;ck, D., Holmquist, L., Juhn, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Round+window+membrane+permeability.+An+in+vitro+model.">Round window membrane permeability. An in vitro model.</a> Acta Otolaryngol Suppl. 457, 73-77 (1989).</li><li>Moatti, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+drug+permeability+through+an+ex+vivo+porcine+round+window+membrane+model.">Assessment of drug permeability through an ex vivo porcine round window membrane model.</a> iScience. 26 (6), 106789 (2023).</li><li>Lin, Y. 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In local drug delivery to the ear, the RWM is the primary route of passage for therapeutics to reach the inner ear. An accurate and reliable benchtop model is needed to better understand transport mechanisms and permeability across novel delivery vehicles and for drug development. In this study, we demonstrate that guinea pig RWM explantation is a feasible and dependable procedure to allow for systematic investigations of drug-membrane interactions. Lundman et al. and Kelso et al. previously described utilizing a similar...

Novel classes of therapeutics have emerged for the treatment of sensorineural hearing loss. The translation of these therapeutics to clinical populations is limited by safe and efficacious routes of transport into the inner ear. Current methods of in vivo delivery in animal studies rely on either fenestration into the inner ear or diffusion through the round window membrane (RWM), a non-osseous barrier that separates the middle ear space from the cochlea1.
Surgical fenestration and microinjection into the inner ear are both invasive and can pose risks to residual inner ear function2. Therefore, the RWM is an important route for local drug delivery, and guinea pigs are the primary preclinical animal model used to study local drug pharmacokinetics across the RWM and in the inner ear for pharmaceutical development3,4. Although thinner than the human RWM, the guinea pig RWM shares an identical three-layered structure. It is approximately 1 mm in diameter, 15-25 &#181;m thick, and comprised of two epithelial cell layers sandwiching a connective tissue layer5. The epithelial layer facing the middle ear is densely packed and connected via tight junctions, while the layer facing the inner ear and scala tympani has looser architecture and does not have significant intercellular adhesions.
Current pre-clinical studies investigating drug permeability in the guinea pig RWM rely on in vivo middle ear injections followed by the sampling of the perilymph fluid within the inner ear, which does not allow for the specific study of RWM transport6,7. Fragments of RWM explants have been used in preclinical studies, but due to their fragility and small size, they are not suitable for systematic, microfluidic investigations of drug and vehicle transport requiring a watertight seal across the RWM2. Other groups have employed in vitro models with cultured human epithelial cells to approximate the RWM8,9,10. However, the majority of these constructs focus solely on the outer epithelial layer and do not capture the complexity of native tissue architecture. For a more detailed understanding of transport mechanisms across the RWM, targeted, ex vivo studies are required.
In this study, we demonstrate the explantation of a guinea pig RWM with surrounding bony support to preserve membrane integrity and illustrate their use in an experimental paradigm designed for the specific study of the RWM transport of drug delivery vehicles.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1 mm Diamond Ball Drill Bit</td>
			<td>Anspach</td>
			<td>1SD-G1</td>
			<td></td>
		</tr>
		<tr>
			<td>2 mm Diamond Ball Drill Bit</td>
			<td>Anspach</td>
			<td>2SD-G1</td>
			<td></td>
		</tr>
		<tr>
			<td>6 mm Diamond Ball Drill Bit</td>
			<td>Anspach</td>
			<td>6D-G1</td>
			<td></td>
		</tr>
		<tr>
			<td>ANSPACH EMAX 2 Plus System</td>
			<td>Anspach</td>
			<td>EMAX2PLUS</td>
			<td>Any bone cutting drilling system will work</td>
		</tr>
		<tr>
			<td>BD Eclipse Needle 27 G x 1/2 in. with detachable 1 mL BD Luer-Lok Syringe</td>
			<td>Becton, Dickinson, and Co.&#160;</td>
			<td>382903057894</td>
			<td>Any 27-28 G needle</td>
		</tr>
		<tr>
			<td>Gorilla Epoxy</td>
			<td>Gorilla</td>
			<td>4200101</td>
			<td></td>
		</tr>
		<tr>
			<td>Kwik-CAST</td>
			<td>World Precision Instruments</td>
			<td>KWIK-CAST</td>
			<td></td>
		</tr>
	</tbody>
</table>

guinea pig round window membrane explantation for ex vivo studies

Efficient and minimally invasive drug delivery to the inner ear is a significant challenge. The round window membrane (RWM), being one of the few entry points to the inner ear, has become a vital focus of investigation. However, due to the complexities of isolating the RWM, our understanding of its pharmacokinetics remains limited. The RWM comprises three distinct layers: the outer epithelium, the middle connective tissue layer, and the inner epithelial layer, each potentially possessing unique delivery properties.
Current models for investigating transport across the RWM utilize in vivo animal models or ex vivo RWM models which rely on cell cultures or membrane fragments. Guinea pigs serve as a validated preclinical model for the investigation of drug pharmacokinetics within the inner ear and are an important animal model for the translational development of delivery vehicles to the cochlea. In this study, we describe an approach for explantation of a guinea pig RWM with surrounding cochlear bone for benchtop drug delivery experiments. This method allows for preservation of native RWM architecture and may provide a more realistic representation of barriers to transport than current benchtop models.

Author Spotlight: Extraction of Guinea Pig Round Window Membrane to Facilitate Inner Ear Drug Delivery Research

Guinea Pig Round Window Membrane Explantation for Ex Vivo Studies

Our group is investigating drugs and drug delivery vehicles for the treatment of inner ear diseases such as hearing loss. The round window membrane is the critical barrier that prevents locally applied drugs from getting into the cochlea and we're currently working to understand how nanoparticle delivery vehicles can be engineered to pass through this barrier. Understanding how the round window membrane works in terms of drug transport is crucial in developing effective drug delivery strategies to the ear.Guinea pig is an important preclinical animal model for studying drug delivery to the ear. However, isolating this fragile membrane, which is only 17 microns thick, for drug transport studies remains a significant challenge. Here, we describe a method for extracting the guinea pig round window membrane that allows for efficient bench top drug transport studies.Current investigations of drug delivery to the inner year rely primarily on in vivo experimental models followed by perilymph sampling which do not allow for a specific and targeted study of round window membrane transport mechanisms. In this study, we demonstrate the extraction of the guinea pig round window membrane with surrounding bony support. This method preserves native tissue architecture integrity and allows for precise and targeted studies of drug delivery across the round window membrane.

As demonstrated in Figure 3A, this method allows for the explantation of the intact guinea pig round window membrane with a surrounding ring of rigid bone. The RWM should be fully connected to the bony annulus circumferentially. No fractures of the cochlear bone should be appreciated. In comparison with human round window specimens, guinea pig RWM does not have an overlying pseudomembrane. Additionally, unlike humans, there is a bony bridge between the crura of the guinea pig stapes, which r...

Watch this Scientific Journal Video about Author Spotlight: Extraction of Guinea Pig Round Window Membrane to Facilitate Inner Ear Drug Delivery Research at JoVE.com

This protocol outlines a method for the explantation of the round window membrane from guinea pig temporal bones, providing a valuable resource for ex vivo studies.

Efficient and minimally invasive drug delivery to the inner ear is a significant challenge. The round window membrane (RWM), being one of the few entry ...

guinea-pig-round-window-membrane-explantation-for-ex-vivo-studies

Research

JoVE Journal

Biology

473 ビュー.  Johns Hopkins School of Medicine. 当グループでは、難聴などの内耳疾患の治療のための薬剤や薬物送達担体の研究を行っています。丸い窓の膜は、局所的に塗布された薬剤が蝸牛に入るのを防ぐ重要な障壁であり、私たちは現在、この障壁を通過するようにナノ粒子送達車をどのように設計できるかを理解しようとしています。丸窓膜が薬物輸送の観点からどのように機能するかを理解することは、耳?...

ビデオ: 著者スポットライト:内耳薬物送達研究を促進するためのモルモット丸窓膜の抽出

This protocol outlines a method for the explantation of the round window membrane from guinea pig temporal bones, providing a valuable resource for ex vivo...

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surgical method for virally mediated gene delivery to the mouse inner ear through the round window membrane

Surgical Method for Virally Mediated Gene Delivery to the Mouse Inner Ear through the Round Window Membrane

The described post-auricular surgical approach allows rapid and direct delivery into the mouse cochlear scala tympani while minimizing blood loss and animal mortality. This method can be used for cochlear therapy using molecular, pharmacologic and viral delivery to postnatal mice through the round window membrane.

surgical procedure for explantation of round window membrane from guinea pig temporal bones

Surgical Procedure for Explantation of Round Window Membrane from Guinea Pig Temporal Bones

a comparative study of drug delivery methods targeted to the mouse inner ear: bullostomy versus transtympanic injection

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

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...

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

canalostomy for local drug delivery into the inner ear of an adult mouse

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&#39;s inner...

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

cochlear implantation in the guinea pig

Cochlear Implantation in the Guinea Pig

The goal of this protocol is to provide an animal model of cochlear implantation, which can be used to address a multitude of research questions. Potential applications include the evaluation of pharmaceutical interventions or electrical stimulation for beneficial effects on hearing thresholds or electrode...

Next place, the animal in the right lateral position to facilitate surgery on the left ear. Make a one to 1.5-centimeter postauricular incision, three millimeters from the left retroauricular groove. Note, when the root of the pinna is defined as the origin, and the plane parallel to the calvarium as 3 to 9 o&#39;clock, the posterior semicircular canal and the lateral semicircular canal are typically located about three millimeters from the root of the pinna between 2 and 3...

use of micropipette-guided drug administration as an alternative method to oral gavage in rodent models

Author Spotlight: Advancing Animal Research with Less Invasive Drug Administration

Here, we describe micropipette-guided drug administration (MDA) as an alternative method to oral gavage that incentivizes the research animal to ingest treatments readily with minimal stress and discomfort.

Reducing Research Animal Stress with Micropipette-Guided Drug Administration

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mouse inner ear extraction and stria vascularis dissection

Mouse Inner Ear Extraction and Stria Vascularis Dissection  

posterior semicircular canal approach for inner ear gene delivery in neonatal mouse

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

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...

the mouse round-window approach for ototoxic agent delivery: a rapid and reliable technique for inducing cochlear cell degeneration

The Mouse Round-window Approach for Ototoxic Agent Delivery: A Rapid and Reliable Technique for Inducing Cochlear Cell Degeneration

Various methods exist for introducing ototoxic agents to the cochleae of animal models. Presented is a surgical protocol for delivery of ototoxic agents to the round window niche. The procedure is reliable, creates targeted intra-cochlear lesions, and avoids mechanical damage to the microarchitecture. Examination of cochlear self-repair/regeneration is possible.

a revised surgical approach to induce endolymphatic hydrops in the guinea pig

A Revised Surgical Approach to Induce Endolymphatic Hydrops in the Guinea Pig

This article demonstrates an extradural approach to obliterate the guinea pig endolymphatic sac and injure the endolymphatic duct with a fine pick in order to induce experimental endolymphatic...

canalostomy as a surgical approach to local drug delivery into the inner ears of adult and neonatal mice

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

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...

gene transfer to the developing mouse inner ear by in vivo electroporation

Gene Transfer to the Developing Mouse Inner Ear by In Vivo Electroporation

The mouse inner ear is a placode-derived sensory organ whose developmental program is elaborated during gestation. We define an in utero gene transfer technique consisting of three steps: mouse ventral laparotomy, transuterine microinjection, and in vivo electroporation. We use digital video microscopy to demonstrate the critical experimental embryological...

Gene Transfer to the Developing Mouse Inner Ear by In Vivo Electroporation

isolation of retinal pigment epithelial cells from guinea pig eyes

Isolation of Retinal Pigment Epithelial Cells from Guinea Pig Eyes

We describe a simple and efficient method for isolating cells of the retinal pigment epithelium (RPE) cells from the eyes of young pigmented guinea pigs. This procedure allows for follow-up molecular biology studies on the isolated RPE, including gene expression...

direct delivery of mif morpholinos into the zebrafish otocyst by injection and electroporation affects inner ear development

Direct Delivery of MIF Morpholinos Into the Zebrafish Otocyst by Injection and Electroporation Affects Inner Ear Development

A method to deliver morpholinos directly into the zebrafish otocyst at 24hpf has been developed.   Using microinjection of morpholinos into the lumen of otic vesicle and electroporation to effect penetration, we were able to bypass the effect of morpholinos on the brain and obtain effects specific to the inner...

optimized interferon-gamma elispot assay to measure t cell responses in the guinea pig model after vaccination

Optimized Interferon-gamma ELISpot Assay to Measure T Cell Responses in the Guinea Pig Model after Vaccination

The development of the interferon-gamma ELISpot assay for guinea pig PBMCs allows the characterization of T-cell responses in this highly relevant model for studying infectious diseases. We have applied the assay to measure T cell responses associated with intradermal delivery of DNA...

in ovo and ex ovo methods to study avian inner ear development

In Ovo and Ex Ovo Methods to Study Avian Inner Ear Development

The chick is a cost-effective, accessible, and widely available model organism for a variety of studies. Here, a series of protocols is detailed to understand the molecular mechanisms underlying avian inner ear development and regeneration.