# Mouse Vocal Fold Permeability In Vivo: Effects of Novel Low‐Tech Injury and Instillation Methods

## TL;DR

This study shows that simple, low-tech methods can injure and deliver substances to mouse vocal folds, revealing their natural high permeability.

## Contribution

The paper introduces low-tech methods for mouse vocal fold injury and instillation, demonstrating their inherent permeability.

## Key findings

- High-dose naphthalene reliably injures mouse vocal folds.
- Oropharyngeal aspiration effectively delivers substances to mouse vocal folds.
- Mouse vocal fold epithelium is naturally highly permeable to low molecular weight dyes.

## Abstract

Vocal fold (VF) injury and instillation are emerging techniques to study laryngeal pathologies in mouse models. Most approaches require high‐tech visualization and lengthy anesthesia. Intraperitoneal (IP) naphthalene (NAPH) and topical polidocanol (PDOC) are two chemical methods of injuring murine lower airways. Oropharyngeal aspiration (OA) is used for murine lung instillation. We assessed whether these simple low‐tech methods could injure and instill mouse VFs, and whether injury increased in vivo VF epithelial permeability.

Mouse VFs were injured using IP NAPH at 200, 250, 300, or 350 mg/kg, or OA of PDOC at 0.5% or 2% w/v. Twenty‐four hours later, mice received Evans blue (EB) dye OA instillation, then were sacrificed after 30 min. Coronal larynx sections were assessed for VF injury. Permeability was measured by imaging EB autofluorescence and quantifying percent positive area and signal intensity. VFs were immunostained for basal cells (p63), tight junctions (ZO‐1), and basement membrane (laminin).

VF injury was 100% with 350 mg/kg NAPH or high‐volume 2% PDOC and 0%–40% with other treatments. EB bound VF lamina propria in up to 100% of mice in a volume‐dependent manner. Permeability did not differ by injury. Basal cells and tight junctions were decreased in injured VFs. Basement membrane was largely intact.

High‐dose NAPH consistently injures mouse VFs. OA reliably instills mouse VFs. Uninjured murine VF epithelium is highly permeable to low molecular weight dye in vivo. Inherent permeability of mouse VFs may facilitate targeted genetic engineering approaches and studies of environmental hazards and drug treatments.

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Improving experimental mouse vocal fold injury and instillation approaches is necessary to advance preclinical models of laryngeal disease. We have successfully repurposed low‐tech, quick, and reliable injury and instillation methods established in respiratory research. Using these methods, we show that murine vocal fold epithelium is inherently highly permeable, and that permeability does not increase with injury.