脑卒中模型小鼠神经纤维束的磁共振成像分析

Application of magnetic resonance imaging in nerve fiber tract analysis in a mouse model of stroke

目的采用11.7 Tesla(11.7 T)磁共振成像(magnetic resonance imaging,MRI)技术评价小鼠大脑中动脉阻塞(middle cerebral artery occlusion,MCAO)再灌注模型后脑梗死体积及神经发生相关脑区间的神经纤维连接情况。方法成年雄性SPF级C57BL/6小鼠,采用线栓法建立MCAO模型,并分别在造模前3 d和造模后1 d进行磁共振扫描。勾画梗死区域并计算梗死体积,对特定脑区进行神经纤维追踪,并分析各向异性分数(fractional anisotropy,FA)、平均扩散系数(mean diffusivity,MD)、轴向扩散系数(axial diffusivity,AD)、径向扩散系数(radial diffusivity,RD)等数据。采用SPSS 26.0进行统计分析,造模前后数据比较采用配对t检验。结果(1)与造模前相比,MCAO造模后,小鼠梗死体积达到[(35.11±17.57)mm3],梗死区域的FA值减少(t=4.73,P<0.01)。(2)对前囟(anterior posterior,AP):+1.2 mm切面进行纤维追踪,发现与造模前相比,造模后从侧脑室背侧角投射到皮层的纤维束数量由(92584.20±14751.00)个减少为(59815.60±6752.46)个(t=4.87,P<0.01),投射到梗死区域的纤维束数量由(107671.40±10497.57)个减少为(61658.60±10178.21)个(t=6.43,P<0.01)。FA、AD、MD、RD值均有不同程度的减少(t=3.38~6.43,均P<0.05)。(3)对AP:-3.8 mm切面进行纤维追踪,发现从侧脑室背侧角投射到皮层的纤维束数量造模后由(96944.00±18331.09)个减少为(58767.80±16445.25)个(t=2.99,P<0.05),FA、AD、MD、RD值均降低(t=7.30,5.05,6.74,4.13,均P<0.05)。结论11.7 T超高场强磁共振成像技术精准检测到小鼠缺血再灌注1 d后从侧脑室背侧角投射到皮层和梗死区的神经纤维束数量和扩散张量参数均显著下降。

Objective To evaluate the cerebral infarct volume and the nerve fiber connectivity between cortical and neurogenesis-related regions in the mouse model of reperfusion after middle cerebral artery occlusion(MCAO)by 11.7 Tesla(11.7 T)magnetic resonance imaging(MRI).Methods MCAO models were established in SPF grade adult male C57BL/6 mice using the suture-occluded method.MRI scans were performed at 3 days before and 1 day after modeling.Infarct volumes were calculated,and nerve fiber tracking was performed on specific brain regions to analyze the nerve fiber number and the parameters of fractional anisotropy(FA),mean diffusivity(MD),axial diffusivity(AD)and radial diffusivity(RD).SPSS 26.0 was used for statistical analysis,and paired t test was used to compare the data before and after modeling.Results(1)After MCAO-induced ischemia,the infarct volume was up to(35.11±17.57)mm3,and the FA value of the infarct area was significantly reduced compared with that of before modeling(t=4.73,P<0.01).(2)At the anterior-posterior(AP):+1.2 mm section,the results of fiber tracking showed that compared with before modeling,the number of fiber bundles originating from the dorsal horn of the lateral sub-ventricle zone(SVZ)to the cortex reduced((92584.20±14751.00)vs(59815.60±6752.46),t=4.87,P<0.01),and the number of fiber bundles projected to the infarcted area reduced((107671.40±10497.57)vs(61658.60±10178.21),t=6.43,P<0.01).FA,AD,MD,and RD values were all decreased in different degrees(t=3.38-6.43,all P<0.05).(3)At the AP:-3.8 mm section,the number of fiber bundles originating from the dorsal horn of the SVZ to the cortex decreased(after modeling(96944.00±18331.09),before modeling(58767.80±16445.25),t=2.99,P<0.05),and the values of FA,AD,MD and RD decreased after ischemia(t=7.30,5.05,6.74,4.13,all P<0.05).Conclusion The ultra-high field strength of 11.7 T MRI can accurately detect the following results that the number of nerve fiber bundles from the SVZ to the cortex or infarct area are both significantly reduced,and diffusion tensor parameters are consistently changed in mice after 1 day of ischemia-reperfusion.