Regeneration of the mammalian vestibular sensory epithelium following gentamicin-induced damage.
OBJECTIVE
The aims of this study are (1) to investigate if significant long-term recovery of mature hair bundle (MHB) numbers takes place following gentamicin-induced damage to the mammalian vestibular sensory epithelium and (2) to assess if the different MHB types in the vestibular sensory epithelium have a different susceptibility to ototoxic damage.


METHODS
Gentamicin (8 mg in 0.1-mL sterile water) was injected transtympanically into one ear of guinea pigs, the contralateral ear acting as a control. The animals were killed at 4 days, 4 weeks, and 3 and 10 months post-treatment and the utricles (n = 38) were extracted from both ears. Mature hair bundle and immature-looking hair bundle (IHB) densities on the surface of the utricle were determined using scanning electron microscopy.


RESULTS
The MHB density showed a significant decline between 4 days and 4 weeks post-treatment. There was greater loss of type I MHBs (tallest stereocilia comparable in height to the kinocilium) than type II MHBs (kinocilium taller than the tallest stereocilia). A significant increase in IHB density was seen at 4 weeks post-treatment, after which it declined rapidly. A significant but incomplete recovery in MHB density (to 66% of control value) was seen in the striolar region at 10 months post-treatment, and these were composed mainly of type II MHBs.


CONCLUSIONS
It would appear that the mature mammalian vestibular sensory epithelium does have the capacity for long-term recovery of MHB numbers following gentamicin-induced damage, but this is limited and does not result in complete restoration of the epithelium. Type I MHBs are more susceptible to ototoxic damage than type II MHBs. Sommaire
Walsh
R M
RM
Department of Otolaryngology-Head and Neck Surgery, Beaumont Hospital, Dublin, Ireland.
Hackney
C M
CM
Furness
D N
DN
D000818:Animals; D000900:Anti-Bacterial Agents / Q000009:adverse effects*; D002452:Cell Count; D005260:Female; D017950:Ganglia, Sensory / Q000187:drug effects* / Q000502:physiology* / Q000648:ultrastructure; D005839:Gentamicins / Q000009:adverse effects*; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D008297:Male; D012038:Regeneration / Q000502:physiology*; D013997:Time Factors; D014722:Vestibule, Labyrinth / Q000187:drug effects* / Q000502:physiology* / Q000648:ultrastructure
D000900:Anti-Bacterial Agents; D005839:Gentamicins