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

Guinea Pig Round Window Membrane Explantation

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.

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.

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

Research

JoVE Journal

Biology

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 ...