胶质细胞源性神经营养因子体内转基因治疗对脊髓运动神经元的保护作用

Protective effect of liposome-mediated GDNF gene transfer in vivo on motor neur ons following spinal cord injury in rats

目的研究脂质体介导胶质细胞源性神经营养因子(GDNF)体内转基因对大鼠脊髓损伤(SCI)后脊髓前角运动神经元的保护作用.方法雄性SD大鼠50只随机均分为绿色荧光蛋白(GFP)组和GDNF组.采用改良Nystrom法制备大鼠脊髓急性压迫损伤模型,将脂质体DC-Chol和重组质粒pEGFP-GDNF cDNA混合后注入大鼠损伤脊髓.利用RT-PCR技术和荧光显微镜检测GDNF基因体内转染的表达;应用尼氏染色、酶组织化学染色方法观察SCI后伤区前角运动神经元存活的数目和胆碱酯酶(CHE)及酸性磷酸酶(ACP)的变化;采用斜板试验和BBB评分观察大鼠后肢运动功能恢复情况.结果SCI后1周和4周GDNF在损伤局部有转录和蛋白水平高表达.SCI后第1、2、4周,GDNF组前角运动神经元存活数目(20.4±3.2、21.7±3.6、22.5±3.4)明显多于GFP组(16.8±2.8、17.3±2.7、18.2±3.2)(P＜0.05).SCI后第1、2周,GDNF组前角运动神经元中CHE平均灰度值(74.2±25.8,98.7±31.6)低于GFP组(98.5±32.2,134.6±45.2)(P＜0.01),ACP平均灰度值(84.5±32.6,79.5±28.4)高于GFP组(61.2±24.9,52.6±19.9)(P＜0.01).大鼠SCI后1～4周,GDNF治疗组后肢运动功能评分明显高于GFP对照组,两组间差异有显著性意义(P＜0.05).结论GDNF体内转基因能保护脊髓不完全性损伤后引起的神经元坏死和退变,促进大鼠后肢运动功能的恢复,提示阳离子脂质体介导GDNF体内转基因治疗SCI的方法是可行的.

Objective To investigate the effect of liposome-m ediated GDNF in vivo gene transfer on spinal cord motor neurons after spinal c ord injury in adult rats.Methods Sixtymale Sprague-Dawley rats were divided eq ually into two groups:GDNF group and GFP group.The SCI model of acute spinal cord post-erior com pression was established according to the method of Nyst rm,and then The DC-Chol liposome and recom binant plasmid pEGFP-GDNF cD N A complexes were injected into the injured spinal cord.The expres-sion of GDN F cDNA after injection was detected by RT-PCR and fluorescence mi cro scope.T he remaining motor neurons in anterior horn and the changes of cholinesterase (CHE)and acid phosphatase(ACP)activity were observed by using Nissl and enzy me histo chemistry staining.The locomo tion function of hindlimbs of rats was evaluated using inclined plane test and BBB loco motor scale.Results RT-PCRan d fluorescence observa-tion confirmed the presence of ex pression of GDNF cDN A at1week and4weeks after injection.At 1,2,4weeks after SCI,the number of active motor neurons in anterior horn in GDNF group(20.4±3.2,2 1.7±3.6,22.5±3.4)was more than that in GFP group(16.8±2 .8,17.3±2.7,18.2±3.2)(P<0.05).At 1,2weeks after SCI,the mean gray value of the CHE stained spinal motoneurons in GDNF group( 74.2±25.8,98.7±31.6)was less than that in GFP group(98. 5±32.2,134.6±45.2)(P<0.01),the mean gray value of ACP in GDNF group(84.5±32.6,79.5±28.4)was more than that in G FP group(61.2±24.9,52.6±19.9)(P<0.01).The lo comoti ve functional scales of rats in GDNF group were high er than that in GFP group within1to4weeks after SCI (P<0.05).Conclusion GDNFin vivo gene transfe r could protect motoneu rons from death and degeneration in-duced by incomplete d spinal cord injury as well as en hance locomotive function al restora tion of hindlimbs.The results suggest that li po some-medi-ated delivery of GDNF cDNA might be a practical method to treat traumatic spinal cord in jury.