Gentamicin ototoxicity: histological and ultrastructural alterations after transtympanic administration

Area of Science:

• Ototoxicology
• Inner Ear Histology
• Vestibular System Research

Background:

• Gentamicin is an aminoglycoside antibiotic with known ototoxic potential.
• Understanding the specific cellular effects of gentamicin on the inner ear is crucial for managing side effects.

Purpose of the Study:

• To investigate the histological and ultrastructural effects of transtympanic gentamicin administration on the guinea pig inner ear vestibulum.
• To identify cellular damage in vestibular sensory and non-sensory components.

Main Methods:

• Guinea pigs received a single transtympanic dose of 4% gentamicin sulphate in the right ear.
• Vestibula from treated and control (left ear) inner ears were examined using light microscopy and transmission electron microscopy (TEM).
• Histological and ultrastructural changes were documented 7 days post-administration.

Main Results:

• Light microscopy showed variable damage, including disepithelialization of cristae ampullares in some cases.
• Transmission electron microscopy revealed significant damage to vestibular non-sensory cells, characterized by severe vacuolation.
• Sensory vestibular cells exhibited heterochromatic thickenings and cytoplasmic wrinkling; nerve fibers and tunica fibrosa also showed alterations.

Conclusions:

• Transtympanic gentamicin causes ultrastructural damage to the inner ear vestibular system in guinea pigs.
• Non-sensory vestibular cells are particularly susceptible to gentamicin-induced damage.
• TEM is essential for detecting subtle gentamicin-induced ototoxicity not apparent under light microscopy.