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Sensory hair fusion and glycocalyx changes after gentamicin exposure in the guinea pig
M Takumida1, J Wersäll, D Bagger-Sjöbäck
1Department of Otolaryngology, Karolinska Institutet, Karolinska Sjukhuset, Stockholm, Sweden.
Abstract:
This study demonstrates the mechanism of sensory hair fusion and its relationship to glycocalyx on the inner ear sensory cells of gentamicin-treated guinea pigs, using the ruthenium red staining technique. 0.5 ml containing 5 mg gentamicin sulfate solution was injected in a single dose into the middle ear. After 7 days, various stages of sensory hair degeneration could be observed. The glycocalyx was clearly visualized by ruthenium red. The degeneration starts with a decrease in or even complete loss of glycocalyx in the sensory hairs, with subsequent local adhesion of the plasma membrane in neighbouring hairs. These findings suggest that the glycocalyx of the sensory cell may play an important role in separating the cilia, yet keeping them in a bundle.
Insights
Gentamicin treatment causes inner ear sensory hair fusion by damaging the glycocalyx. This protective layer normally separates cilia, but its loss leads to adhesion and degeneration, impacting hearing.
Area of Science:
- Ototolaryngology
- Cell Biology
- Neuroscience
Background:
- Inner ear sensory cells possess specialized hair bundles crucial for hearing and balance.
- Gentamicin is a known ototoxic antibiotic that can damage these sensory cells.
- The glycocalyx, a carbohydrate-rich layer, coats cell surfaces and its role in hair bundle integrity is not fully understood.
Purpose of the Study:
- To elucidate the mechanism of sensory hair fusion in the inner ear following gentamicin exposure.
- To investigate the relationship between the glycocalyx and sensory hair degeneration.
- To understand the role of the glycocalyx in maintaining sensory hair bundle structure.
Main Methods:
- Guinea pigs were treated with a single dose of gentamicin sulfate via middle ear injection.
- Sensory hair degeneration was assessed after 7 days.
- Ruthenium red staining was employed to visualize the glycocalyx on inner ear sensory cells.
Main Results:
- Gentamicin treatment induced various stages of sensory hair degeneration.
- Ruthenium red staining clearly visualized the glycocalyx.
- Degeneration initiated with a reduction or complete loss of glycocalyx on sensory hairs.
- Loss of glycocalyx was followed by local adhesion of adjacent hair cell membranes.
Conclusions:
- The glycocalyx plays a critical role in maintaining the separation of sensory cilia within a bundle.
- Damage to the glycocalyx is a key mechanism in gentamicin-induced sensory hair fusion and degeneration.
- Understanding this mechanism may inform strategies to protect against ototoxicity.