Acute Response of Neurons: An Early Event of Neuronal Cell Death After Facial Nerve Injury.

OBJECTIVE: To research the early acute response events of facial nerve injury.

METHODS: Sixty male Sprague-Dawley rats were randomly divided into 2 groups. Facial nerve anastomosis was performed for rats in study group. Rats in control group underwent the same surgical procedure, but without cutting off the facial nerve. Before nerve anastomosis and at days 1, 3, 7, 14, and 28 after nerve anastomosis, 5 rats of each group were selected and right side brainstem tissue samples containing the facial nerve nucleus were obtained. Hematoxylin and eosin (H&E) staining and TUNEL detection was performed to observe facial neurons changes. Facial neurons mortality and apoptosis were studied. Expression of caspase-3, LC3, and Beclin1 was detected with Western blot assay.

RESULTS: In study group on day 7 day after nerve anastomosis, Nissl body dissolution and apoptotic facial neurons were significantly increased, the typical polygonal shape and swollen cells disappeared, the number of facial neurons was significantly lower, and the number of apoptotic facial neurons was significantly higher (P < 0.01). In addition, facial neuron mortality rate was significantly increased at day 7, reaching the peak at day 14. Expression of caspase-3, LC3, and Beclin1 was also significantly up-regulated after nerve anastomosis.

CONCLUSION: Nissl body dissolution, typical polygonal shape disappearing, cell swelling, facial neuron mortality and apoptosis, and up-regulated expression of caspase-3, LC3, and Beclin1 are the early events of cell death after facial nerve injury, which are the important precursors to facial nerve injury.