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Permeability of the round window membrane to horseradish peroxidase in experimental otitis media
1Department of Otolaryngology, College of Medicine, Seoul National University, Korea.
Abstract:
The permeability of the round window membrane (RWM) was studied by using horseradish peroxidase (HRP) in the different stages of otitis media developed in guinea pigs, and it was compared with normal RWM under transmission electron microscopic examination. The experimental model of otitis media was developed by inoculation of a Pseudomonas aeruginosa suspension. When HRP could penetrate into the inner layer of a normal RWM, the duration of HRP instillation into the round window niche was 10 minutes. The permeability of the RWM in otitis media was as follows: 3-day animals showed penetration of HRP into the middle layer. In 1-week animals, HRP had penetrated into the inner layer in all 10 ears. In 2-week animals, HRP had penetrated into the inner layer in 6 of 11 ears. In 4-week animals, however, HRP was not seen in 6 of 7 ears. HRP had penetrated through the damaged focus of the epithelial cells by inflammation. These results suggest that any derangement of the epithelial linings could increase the penetration of HRP and also ototoxic materials into the inner ear through the RWM.
Insights
Otitis media damages the round window membrane (RWM) barrier, increasing inner ear exposure. Inflammation disrupts RWM integrity, allowing horseradish peroxidase (HRP) and ototoxic substances to penetrate.
Area of Science:
- Otolaryngology
- Pathology
- Microscopy
Background:
- The round window membrane (RWM) is a critical barrier protecting the inner ear.
- Otitis media, an middle ear infection, can compromise this barrier.
- Understanding RWM permeability during otitis media is vital for preventing inner ear damage.
Purpose of the Study:
- To investigate the permeability changes of the RWM during experimental otitis media.
- To compare the permeability of normal RWM with RWM affected by otitis media using horseradish peroxidase (HRP).
Main Methods:
- An experimental otitis media model was created in guinea pigs by inoculating Pseudomonas aeruginosa.
- Horseradish peroxidase (HRP) was instilled into the round window niche for 10 minutes.
- RWM permeability was assessed using transmission electron microscopy at different stages of otitis media (3 days, 1 week, 2 weeks, 4 weeks).
Main Results:
- In normal RWM, HRP penetrated the inner layer within 10 minutes.
- During otitis media, HRP penetration increased, reaching the inner layer by 1 week.
- HRP passage occurred through damaged epithelial cells, suggesting inflammation-induced breaches.
Conclusions:
- Inflammation associated with otitis media significantly increases RWM permeability.
- Damage to the RWM's epithelial lining facilitates the entry of HRP and potentially ototoxic substances into the inner ear.
- Maintaining RWM integrity is crucial for preventing inner ear complications in otitis media.
