大鼠脊髓挫伤后BDNF表达的实验性研究

目的探讨大鼠脊髓挫伤后脑源性神经营养因子(BDNF)在脊髓内的表达变化规律。方法建立大鼠脊髓挫伤模型,以正常脊髓组织为对照,采用RT-PCR和免疫组化SABC法对伤后即刻、1h、3h、6h、12h、1d、3d、5d、7d大鼠脊髓组织中的BDNF和BDNF mRNA进行检测,并对所得数据进行统计学分析。结果正常大鼠脊髓组织细胞内有低水平的BDNF mRNA表达和少量BDNF阳性染色细胞,BDNF mRNA和BDNF的积分光密度(IOD)值分别为45.83±3.545、20286.225±2094.955,BDNF阳性细胞数为16.50±3.391;伤后6~12h,BDNF mRNA和BDNF呈升高趋势,5d达高峰,二者的IOD值及阳性细胞数分别为795.83±112.55、54272.143±2704.239和158.17±12.287。伤后7d,BDNF mRNA和BDNF的IOD值及阳性细胞数分别为655.17±80.871、42249.928±809.391和100.17±5.529。各组之间比较,其差异具有统计学意义(P<0.05)。BDNF免疫阳性细胞在损伤早期主要是脊髓神经元和少量星形胶质细胞,后期则以小胶质细胞为主。结论大鼠脊髓挫伤后,脊髓组织细胞中的BDNF及其mRNA增多,并随伤后时间呈现一定规律性变化。

An experimental study on time-dependent expressions of BDNF and BDNF mRNA after spinal cord contusion in rats

Objective To explore the expression pattern and effects of brain-derived neurotrophic factor(BDNF) after spinal cord contusion in rats. Methods The spinal cord contusion model was established by modified Allen’s crush method in rats. Expressions of BDNF mRNA and its protein were detected using RT-PCR and immunohistochemical techniques. The results were analyzed by computerized image analysis system.Results In the control rats, low levels of BDNF and BDNF mRNA were detected in the spinal cord. The integrate optical density (IOD) value of BDNF mRNA and BDNF were 45.83±3.545, 20286.225±2094.955. The number of BDNF-positive cells was 16.50±3.391. Expressions of BDNF and BDNF mRNA up-regulated at 6～12h after injury and reached peak at 5d. IOD values were 795.83±112.55 and 54272.143±2704.239. The BDNF-positive cells number was 158.17±12.287, which were significiant statistically among groups(P<0.05). Thereafter, expressions of both BDNF and BDNF mRNA down-regulated in parallel, which were still highly expressed until 7d post-injury as compared with those of the control(P<0.05). In the early phase of injury, neurons and astrocytes accounted for the most part of BDNF-positive cells. But BDNF-positive cells were mainly microglias in the later phase of injury. Conclusion The results suggest that expressions of BDNF and BDNF mRNA are enhanced time-dependently after spinal cord contusion in rats.