The peripheral processes of spiral ganglion cells after intracochlear application of brain-derived neurotrophic factor in deafened guinea pigs.

OBJECTIVE: To characterize the effects of deafening and subsequent treatment with brain-derived neurotrophic factor (BDNF) on the peripheral processes (PPs) of spiral ganglion cells (SGCs) in guinea pigs.

BACKGROUND: BDNF may prevent degeneration of neural structures after loss of hair cells with possible relevance for cochlear implant candidates.

METHODS: Guinea pigs were deafened with a combination of kanamycin and furosemide. Two weeks after deafening, intracochlear BDNF treatment was started with osmotic pumps for 4 weeks. Two weeks after cessation of BDNF treatment, the cochleae were analyzed. PPs were counted and morphologically characterized with respect to myelination, size, and shape.

RESULTS: Deafening reduced the number of PPs. We found that BDNF treatment, started 2 weeks after deafening, significantly reduced this degenerative effect. The remaining processes showed an altered morphology; compared with normal, the size was reduced in deafened untreated animals and increased in BDNF-treated animals. The myelin sheath seemed thinner in BDNF-treated animals.

CONCLUSION: We conclude that BDNF has potential as an agent that can improve the interface between cochlear implants and the auditory periphery.