# Effect of Intracochlear Brain-Derived Neurotrophic Factor on Guinea Pig Sensorineural Hearing Loss

## TL;DR

This study tested brain-derived neurotrophic factor (BDNF) in guinea pigs with hearing loss but found no improvement in hearing, though blood could be used as a proxy for measuring REDOX potential in the inner ear.

## Contribution

The study introduces the use of blood as a proxy for perilymph REDOX potential in hearing research.

## Key findings

- Two intracochlear BDNF applications did not improve hearing thresholds in guinea pigs with cisplatin-induced hearing loss.
- REDOX potential in blood, cerebrospinal fluid, and perilymph correlates within the same animal, suggesting blood can be used as a proxy for perilymph REDOX measurements.

## Abstract

This study investigates the potential of brain-derived neurotrophic factor (BDNF) as treatment for sensorineural hearing loss (SNHL) in a guinea pig model to potentially advance hearing restoration strategies. The correlation between oxidation-reduction (REDOX) potential in blood and perilymph is evaluated to confirm using blood as a proxy for perilymph in further study.

To evaluate hearing following 2 intracochlear applications of BDNF as a therapy for hearing loss. To evaluate for correlation in REDOX potential of perilymph and auditory brainstem response (ABR).

Positive-control animal preclinical study.

Translational laboratory science.

Animal model (guinea pigs).

SNHL was created in 15 guinea pigs using intraperitoneal cisplatin (CDDP). SNHL was confirmed via ABR testing. Left ears received 2 intracochlear applications of BDNF in varying doses, 30 days apart. Right ears received saline as controls.

Hearing threshold was determined using ABR testing. Animals underwent terminal surgery to measure the REDOX potential in cerebrospinal fluid (CSF) and blood. Analysis of variance for repeated measures using the SPSS v27 software was employed.

Variable, subtotal hearing loss was established utilizing CDDP. Animal ABR thresholds after CDDP, prior to first BDNF application, were worse than baseline. There was no improvement in hearing thresholds when treated and nontreated ears were compared. Varying doses of BDNF did not produce differences in hearing thresholds. The REDOX potential of perilymph, blood, and CSF correlate in the same animal; however, the values themselves were significantly different.

There is no improvement in guinea pig hearing with 2 intracochlear applications of BDNF when applied as described in this paper. Previous work suggested possible subclinical gain with 1 application; however, with 2 applications we found no improvement. The REDOX potential of blood and CSF correlates within an animal, suggesting blood may be used as a proxy for REDOX measures in perilymph.

Graphical Abstract