3-Methyladenine improves the efficiency of sciatic nerve allograft in mice.

BACKGROUND: Recent studies have shown that the occurrence of Wallerian degeneration is closely related to autophagy in Schwann cells. The regulation of autophagy in Schwann cells can significantly affect the occurrence and development of Wallerian degeneration, subsequently altering axon regeneration and myelination. OBJECTIVE: To clarify whether sciatic nerve allograft can achieve higher efficiency when the cell autophagy is inhibited by 3-methyladenine. METHODS: We harvested 16 sciatic nerve segments from 8 female C57BL/6J mice that were purchased from Beijing Vital River Laboratory Animal Technology Co., Ltd. in China. All the segments were equally divided into experimental and control groups and cultured in 3-methyladenine culture medium and nonnal culture medium for 72 hours, respectively. Another 16 female C57BL/6J mice were taken to make animal models of left sciatic nerve defects. After modeling, the sciatic nerve segments were grafted to repair sciatic nerve defect through microsurgery: 3-methyladenine-treated nerve segments in the experimental group and normally treated nerve segments in the control group. Sciatic nerve index in each mouse was recorded at 2, 4, 6, and 8 weeks after modeling. At 8 weeks after modeling, the regenerated nerve segments were histologically analyzed using hematoxylin-eosin staining, immunofluorescent staining, toluidine blue staining, and transmission electron. The animal experiment was approved by the Animal Ethics Committee of Peking Union Medical College. RESULTS AND CONCLUSION: There were no differences in the sciatic nerve index between the two groups (P > 0.05) except at 8 weeks after modeling (P < 0.05). Hematoxylin-eosin staining revealed an intact nerve structure in the experimental group but a large area of voids in the control group. Immunofluorescent staining indicated that there were nerve tracts with more complete structures in the experimental group than the control group. Toluidine blue staining revealed some myelinated and unmyelinated nerve fibers regenerated in the experimental group and only a few of myelinated nerve fibers and unmyelinated axons newly formed in the control group. Under the transmission electron microscope, myelin sheath thickness and myelinated fiber diameter were significantly higher in the experimental group than the control group (P < 0.05). Therefore, 3-methyladenine-treated nerve allografts could inhibit autophagy in Schwann cells, maintain the myelin sheath structure of the allograft, and promote axonal regeneration and functional recovery. [ABSTRACT FROM AUTHOR]