The Peripheral Processes of Spiral Ganglion Cells After Intracochlear Application of Brain-Derived Neurotrophic Factor in Deafened Guinea Pigs

Abstract

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. BDNF may prevent degeneration of neural structures after loss of hair cells with possible relevance for cochlear implant candidates. 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. 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. We conclude that BDNF has potential as an agent that can improve the interface between cochlear implants and the auditory periphery.