Background: The efficacy of cochlear implant performance depends, among many other factors, on the number of excitable spiral ganglion cells (SGCs) and the nerve-electrode interface. In earlier animal studies it has been demonstrated that neurotrophic factors are effective to improve SGC survival after experimentally induced deafness. With regard to their anti-inflammatoric and anti-proliferative effects, glucocorticoids (e. g. dexamethasone) are potentially interesting therapeutic agents to reduce connective tissue formation around the inserted electrode. The biological effects of a combined intervention of neurotrophic factors with steroids on SGCs are unknown. Therefore the objective of the study was to investigate possible trophic or even toxic effects of brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF) and dexamethasone on neurite outgrowth of cultivated SGCs.
Methods: By using dissociated postnatal spiral ganglion cells (p3-5) for cultivation in the present study, the influence of the mentioned factors in various concentrations and combinations on neurite outgrowth of SGCs was analysed.
Results: Our results indicate significant trophic effects for BDNF (50 ng/ml) and a combination of BDNF with dexamethasone (100 ng/ml) on SGC neurite outgrowth. In contrast, single application of GDNF or dexamethasone in different concentrations caused no significant changes on neurite outgrowth when compared to the control condition.
Conclusions: Neurite outgrowth induced by neurotrophic factors could not be observed to be reduced when dexamethasone is given at the same time. Therefore the demonstrated results provide a basis for further animal studies in this field of research.