Abstract: BACKGROUND: Previous studies had shown that hair follicle epidermal neural crest stem cells have the great potential in facilitating peripheral nerve rehabilitation, but the role in regulating inflammation after facial nerve injury had rarely been reported.  
OBJECTIVE: To investigate whether epidermal neural crest stem cells can modify the expression of pro-inflammatory factor tumor necrosis factor α and anti-inflammatory factor interleukin-4 during facial nerve regeneration to promote the functional and morphological recovery of the facial nerve.
METHODS: Epidermal neural crest stem cells were extracted from one 4-day-old SD rat, cultured and identified. Fifty-four adult SD rats were used to construct the bridge model of facial nerve trunk defect with the autologous venous catheter. Models were randomly and equally divided into the normal saline group, Dulbecco's modified eagle medium group and epidermal neural crest stem cell group. Tumor necrosis factor α and interleukin-4 expression levels were detected at postoperative 4 to 14 days using western blotting, immunohistochemistry, and immunofluorescence. The facial nerve function of rats was scored 12 weeks after the operation and the morphology of the facial nerve was observed by hematoxylin-eosin staining.  
RESULTS AND CONCLUSION: (1) Double positive expression of Nestin and p75NTR could be observed in epidermal neural crest stem cells and the cell purity was over 90%. (2) Compared with the other two groups, tumor necrosis factor α expression in the epidermal neural crest stem cell group turned weaker 7 days after surgery (P < 0.05), and interleukin-4 expression in the epidermal neural crest stem cell group was enhanced on postoperative 3, 7 and 14 days, respectively (P < 0.05). (3) The recovery score of facial nerve function in the epidermal neural crest stem cell group was significantly better than that in the other two groups (P < 0.05). (4) There were abundant nutrient vessels and regenerative axons in the graft segment. Compared with the other two groups, the arrangement of nerve fibers was more orderly and the wrapped myelin sheath was thicker in the graft and distal segment in the epidermal neural crest stem cell group. (5) The data inferred that epidermal neural crest stem cells regulate the local expression of tumor necrosis factor α and interleukin-4 at the early stage of facial nerve injury, inhibit the local inflammatory reaction, and improve facial nerve function and morphology of the regenerated nerve.

Key words: facial nerve, nerve regeneration, hair follicle, epidermal neural crest stem cell, inflammatory factor, tumor necrosis factor α, interleukin-4