gms | German Medical Science

Objective: Injury of the cochlear nerve during different surgeries in the cerebellopontine angle (CPA) is frequent. Granulocyte-colony stimulating factor (G-CSF) seems to have a neuroprotective activity by inhibition of apoptosis and of inflammation in various experimental models. The effect of G-CSF to the cochlear nerve and its nuclei has never been reported so far. The purpose of the present study is to investigate the role of G-CSF as a neuroprotective agent after lesion of the cochlear nerve of rats.

Method: A controlled lesion to the right cochlear nerve of adult male Spraque Dawley rats was conducted through a lateral suboccipital craniectomy using a waterjet dissector. Animals were randomly assigned to three groups. G-CSF was applied on day 1, 3 and 5 after surgery (G-CSF post group). In a second group, GCSF was additionally administrated one day before the operation (G-CSF pre&post). The control group (sham) received Sodium chloride. Brainstem auditory evoked potentials (BAEP) were measured on day 1, 3 and 7 after lesion. Histological sections of the cochlear nuclei were prepared and stained with Nissl (cresyl violet). Immunohistochemical studies using Bax and Bcl-2 were additionaly performed.

Results: The evaluation of the histological, immunohistochemical and electrophysiological results demonstrates an improved outcome of the choclear nerve by application of G-CSF. Application of G-CSF led to a significant preservation of neuronal cells in the cochlear nuclei (p=0,0086). Studies using Bax and Bcl-2 showed, in the same way, that GCSF influenced positively on the choclear nuclei (p<0,001). The electrophysiological results revealed a significant lower depression of the BAEP wave II after G-CSF application (p=0,040). Moreover, there was a trend of wave IV in favor of G-CSF (p=0,2676). A benefit through an additional preoperative application of G-CSF, compared to the application after surgery alone, was histologically and electrophysically not observed.

Conclusions: G-CSF improved the function of the eighth cranial nerve and protected cells and tissue on the cochlear nuclei after a controlled partial injury of the nerve in rats. Clinical research about the potential neuroprotective effect of GCSF on the choclear nerve and nuclei of humans could be of great importance. It could possibly improve the post-operative outcome in patients with lesions in the CPA.