B Malgrange

In Vitro Ototoxicity of Aminoglycosides and Platin Derivatives. A Semi-automatic Assay for Sensory Hair Cell Damage in Explanted Rat Organ of Corti

The ototoxic damage that drugs such as neomycin, kanamycin, colistin, cisplatin, transplatin and carboplatin cause on outer and inner hair cells in postnatal day 3 rat cochlear explants was investigated. Phalloidin-fluorescein conjugate-stained stereocilia bundles of sensory hair cells were quantified by video image analysis as a measurement of ototoxic effect. The video image quantification system established dose-response curves for ototoxic drugs (e.g. calculation of an IC(50)) and allowed comparisons between several ototoxins from the same family. This methodology provided the means to assess the efficacy of otoprotectant agents in preventing ototoxicity. Poly-l-aspartate (10(-5)m) and poly-l-glutamate (10(-5)m) protected auditory hair cells from neomycin (10(-3)m) toxicity while reduced glutathione (10(-3)m) provided protection against cisplatin (10(-4)m)-induced hair cell damage.

Herpes Simplex Viral Vector Gene-Based Therapy to Prevent Loss of Auditory Sensory Cells from Stress-Induced Apoptosis

Apoptosis (programmed cell death) plays an important role in both the normal development of the inner ear as well as the response of mature inner sensory cells to damage by toxins, radiation and/or loss of trophic factor support. In the present studies, two Herpes simplex viral vectors (i.e. HSVbdnflac and HSVbc1-2) were used to prevent stress-induced apoptosis of auditory neurons and hair cells, respectively. The first vector HSVbdnflac, expresses genes for both a growth factor (brain derived growth factor) and a cell expression marker (bacterial galactosidase). In vitro studies have shown that this BDNF gene therapy vector can elicit a biological response (i.e. neuritogenesis) from postnatal rat spiral ganglion explants. In an in vivo study, transduction with the HSVbdnflac vector prevented the loss of spiral ganglion neurons from adult mice in which all of the auditory hair cells were destroyed by a scala tympani injection of neomycin. Double label for neurons and viral vector marker protein showed a high level of expression ofHSVbnnflacin the auditory neurons of the spiral ganglion at 1 month post-transduction. At 1 monthpost-transduction, we also observed stable, functional production of BDNF that supported the survival of nearly all (i.e. 94.7% ) of the spiral ganglion neurons and prevented their loss from trophic factor deprivation-induced apoptosis (i.e. 64.3% loss).