Development of histological sectioning techniques for the cochlear implanted inner ear in miniature swine

Background

Cochlear pathological sectioning is essential for studying inner ear structural changes. Traditional methods like paraffin embedding, frozen sectioning, and collodion embedding are limited to decalcified tissues. For cochlear specimens with rigid implants (e.g., cochlear implants), the implant must be separated before decalcification and sectioning. This process often damages the delicate cochlear architecture, compromising pathological integrity. Thus, there is a need for a precise and efficient method for examining cochlear tissues with implants.

New method

We introduce a novel pathological method. First, the cochlea is sectioned and dissected. Then, micro-computed tomography (Micro CT) is used for three-dimensional imaging. Both normal and implant-bearing tissues undergo dehydration, embedding, and staining for histological analysis.

Results

This method produces high-quality sections with uniform thickness, preserves cochlear architecture, and maintains fine structural details. It also enables precise implant localization within the cochlea.

Comparison with existing methods

Our approach allows for dynamic pathological change investigation, three-dimensional mapping of the implant-tissue interface, and micro-damage assessment in implant-bearing cochleae.

Conclusions

This histopathological sectioning method for cochlear-implanted porcine inner ears overcomes previous limitations. It provides a robust method for electrode positioning verification and a standardized framework for evaluating the mechanical-biocompatibility of new electrode designs.

Summary

Cochlear pathological sectioning serves as a critical technique for investigating structural alterations within the inner ear, with conventional methodologies including paraffin embedding, frozen sectioning, and collodion embedding. These techniques, however, are exclusively applicable to decalcified cochlear tissues. The preparation of histopathological sections from cochlear specimens containing rigid implants, such as cochlear implants, necessitates the preliminary separation of the implant from the cochlear tissue, followed by decalcification and subsequent sectioning. This separation process often results in mechanical disruption of the delicate cochlear architecture, thereby compromising the integrity of the inner ear's pathological structure. Consequently, there is a pressing need to develop a precise and efficient methodology for the pathological examination of cochlear tissues with implants. Given that traditional approaches involve prolonged decalcification, existing techniques are inadequate for addressing the challenges associated with implant-bearing cochlear specimens. To address this limitation, we propose a novel, rapid, and efficient pathological method. Initially, the cochlea is sectioned and dissected, followed by three-dimensional imaging using micro-computed tomography (Micro CT). Subsequently, both normal and implant-bearing cochlear tissues undergo dehydration, embedding, and staining for histological analysis. Our findings demonstrate that this method yields high-quality sections with uniform thickness, preserves the cochlear architecture intact, and maintains the fine structural details of the inner ear. Furthermore, it enables precise localization of the implant within the cochlea. This approach facilitates the investigation of dynamic pathological changes in implant-bearing cochleae, three-dimensional mapping of the implant-tissue interface, and assessment of micro-damage. It offers an efficient and non-destructive technical solution for optimizing the compatibility of rigid implants and advancing the pathological study of the inner ear.