No Protective Effects of Hair Cells or Supporting Cells in Ototoxically Deafened Guinea Pigs upon Administration of BDNF

We investigated whether treatment with brain-derived neurotrophic factor (BDNF), which is known to protect spiral ganglion cells (SGCs), could also protect hair cells (HCs) and supporting cells (SCs) in the organ of Corti of a guinea pig model of sensorineural hearing loss. Hearing loss was induced by administration of kanamycin/furosemide and two BDNF treatments were performed: (1) by gelatin sponge (BDNF-GS) with acute cochlear implantation (CI), and (2) through a mini-osmotic pump (BDNF-OP) with chronic CI. Outer HCs (OHCs), inner HCs (IHCs), Border, Phalangeal, Pillar, Deiters’, and Hensen’s cells were counted. The BDNF-GS cochleas had significantly fewer OHCs compared to the untreated ones, while the IHC and SC numbers did not differ between treated and untreated cochleas. The BDNF-OP group showed similar cell numbers to the untreated group. SGC packing density was not correlated with the total number of SCs for either BDNF group. Our data suggest that: (1) BDNF does not prevent cell death in the organ of Corti, and that the protection of SGCs could result from a direct targeting by BDNF; (2) BDNF might induce a different function/activity of the remaining cells in the organ of Corti (independently from cell number).