Abstract: Objective: To establish the rabbit facial nerve injury model by surgery and to explore the repair effect of dental pulp stem cells on the facial nerve injury in the rabbits,and to clarify its possible mechanism. Methods: The dental pulp stem cells were isolated,cultured and induced.A total of 45 rabbits were randomly divided into normal control group,model group and experiment group,and there were 15 rats in each group.Except for normal control group,the rabbits in the other groups were cut along the corner of mouth to the front of the ear to form a incision about 3 cm,the upper buccal branches were disconnected,and the facial nerve buccal injury models were established.After 1 week,0.1 mL dental pulp stem cell suspension (5×10⁶) was injected into the operative cavity of the rats in experiment group, and the rabbits in normal control group did not receive any treatment.The rabbits in model group were injected with the same amount of phosphate buffer (PBS).Two weeks after operation,the behavior and movement function scores of facial beard of the rabbits in various groups were evaluated;the pathomorphology of facial nerve tissue of the rabbits in various groups was observed by HE staining;immunohistochemical staining was used to detect the number of brain derived nerve growth factor (BDNF) and ciliary neurotrophic factor (CNTF) positive cells; the number of regenerated nerve fibers,the diameter of fiber and the thickness of myelin sheath were observed under transmission electron microscope. Results: The primary dental pulp stem cells of young rabbits were successfully separated and identified.Most of them were fibroblast like and long fusiform.The HE staining results showed that the nucleus of the third generation of the dental pulp stem cells showed a dark blue and oval shape,and the spindle shaped hyperchromatic cells were fibroblast like cells.Compared with normal control group,the movement function score of facial beard of the rabbits in model group was significantly decreased(P< 0.05);compared with model group,the movement function score of facial beard of the rabbits in experiment group was increased (P<0.05).Compared with model group,after treated for 10 weeks,there were more regenerated nerve fibers which were fascicular and tight.Compared with normal control group,the number of BDNF and CNTF positive cells in facial nerve tissue section of the rabbits in model group was decressed (P< 0.05);compared with model group,the number of BDNF and CNTF positive cells in facial nerve tissue section of the rabbits in experiment group was significantly increased (P<0.05). Compared with normal control group,the number of regenerated nerve fibers,the diameter of fiber and the thickness of myelin sheath of the rabbits in model group were significantly decreased(P<0.05);compared with model group,the number of regenerated nerve fibers,the diameter of fiber and the thickness of myelin sheath of the rabbits in experiment group were significantly increased (P<0.05). Conclusion: The dental pulp stem cells have a certain repair effect on the facial nerve injury,and the mechanism may be related to the up-regulation of the experessions of BDNF and CNTF.

Key words: dental pulp stem cells, transplantation, disconnection, facial nerve injury