坐骨神经损伤后不同年龄大鼠脊髓组织中bcl-xl基因的表达及变化

Expression and change of B-cell lymphoma/leukemia-xl gene in spinal cord tissues of rats at different ages after injury of sciatic nerve

目的:凋亡可能为大鼠坐骨神经损伤所致脊髓神经细胞损害的一种重要病理改变,而bcl-xl基因有抗细胞凋亡的作用,为此观察坐骨神经损伤后不同年龄大鼠脊髓组织中bcl-xl表达变化。方法:幼年、成年、老年Wistar大鼠各144只,各年龄组大鼠分别随机分为对照组(18只)和实验组(126只)。实验组切除2mm右侧坐骨神经,用硅胶管连接近、远侧神经残端,硅胶管内注入生理盐水15μL。实验组和对照组分为术后1,3d,1,2,4,8,12周组。利用免疫组织化学、West-ernblotting检测脊髓bcl-xl的分布与表达强度变化,流式细胞仪检测凋亡细胞百分率。结果:对照组脊髓凋亡细胞成年及老年<3%、幼年>3%,实验组伤侧脊髓老年及幼年组于伤后3d,成年组于伤后1周凋亡细胞百分率升高,幼年及成年组凋亡细胞百分率2周达高峰(P<0.05或0.01),8,12周凋亡细胞百分率逐渐下降,老年凋亡细胞百分率高水平持续至伤后12周。与同龄对照组及未伤侧比较,各年龄对照组损伤后3d,1,2周,伤侧bcl-xl表达减弱(P<0.05),伤后4周恢复正常,老年组8周,幼年及成年组8周,12周bcl-xl表达较未伤侧及对照组显著增高(P<0.05或0.01)。各年龄组未伤侧与对照组比较,bcl-xl、凋亡细胞百分率差异无显著性意义(P>0.05)。结论:坐骨神经损伤后早期各年龄组神经元bcl-xl表达减弱。

OBJECTIVE:Apoptosis may be an importantly pathologic change of spinal nerve cell injury induced by sciatic nerve injury in rats, and B-cell lymphoma/leukemia-xl gene(Bcl-xl) can resist apoptosis, thereby,to investigate the change of Bcl-xl in spinal cord of rats of different ages after sciatic nerve injury. METHODS:Totally 432 Wistar rats in the young, adult and old rats group with 144 Wistar rats in each group.Wistar rats in each group were randomly subdivided into control group(n=18) and experimental group(n =126).After transection of 2 mm right sciatic nerves,the two nerval ends were connected with collagen tubules in experimental groups, and 15 μL of saline was injected into the collagen tubules. The rats in the experimental group and the control group were subdivided into 1-day,3-day,1-week,two-week,four-week,eight-week and twelve-week groups separately.The distribution and expression of Bcl-xl were detected with immunohistochemistry and Western blotting.The percentage of apoptosis in spinal cord was detected with flow cytomehry. RESULTS:The percentage of apoptosis in the spinal cord in the control group was less than 3%in old and adult rats, and greater than 3%in young rats. The percentage of apoptosis in the injured spinal cord in the experimental groups increased at 3 days in the young and old groups, and at 1 week in the adult group, but reached their peaks at 2 weeks(P< 0.05 or 0.01) and began to decrease at 8 weeks,12 weeks in the adult and young groups respectively,and was still at high level until 12 weeks after injury in the old group. Compared with the same age control group and non-injured contralateral side, the expression of Bcl-xl in the injured spinal cord decreased at 3 days and 1,2weeks in different age groups(P< 0.05) and reached normal level at 4 weeks and it was significantly higher at 8 weeks in old group and at 8,12 weeks in young or adult groups(P< 0.05 or 0.01).There was no significant difference in the expression of Bcl-xl and the percentage of apoptosis between the control groups and contralateral non-injured sides(P >0.05). CONCLUSION:The expression of Bcl-xl in the spinal cord decreased in the early stage following sciatic nerve injury in different age rats.The percentage of apoptosis in the injured spinal cord decreased resulting from increasing the expression of Bcl-xl in the late stage. The change was great in the adult and young group,and weak in the old group.