电针与干细胞治疗大鼠急性周围神经损伤的磁共振扩散张量成像评估

Magnetic resonance diffusion tensor imaging evaluation of electroacupuncture and stem cell therapy for acute peripheral nerve injury in rats

目的运用磁共振扩散张量成像技术(diffusion tensor imaging,DTI)评估电针与干细胞移植在急性周围神经损伤疾病中的治疗效果。材料与方法将48只造模成功的成年SD大鼠随机平均分为电针组、干细胞组和对照组,每组16只。电针组大鼠接受环跳和足三里的电针治疗。干细胞组大鼠于损伤处神经外膜下微量注射3μL含有约5×105个骨髓间充质干细胞的生理盐水悬浊液。对照组显微注射同体积的生理盐水。使用多参数磁共振成像技术包括DTI和磁共振T2加权脂肪饱和序列(T2-weighted fat saturation,T2WI-FS)、组织学评估、免疫组化分析监测神经结构的变化(包括神经直径、髓鞘厚度及形态改变、轴突连续性的恢复)。运用坐骨神经功能指数(somatic functional index,SFI)和步行轨迹分析方法评估神经的运动功能。采用重复测量单因素方差分析不同实验组间大鼠磁共振横向弛豫时间(T2值)、DTI指标[各向异性分数(fractional anisotropy,FA)和径向扩散率(radial diffusivity,RD)]、SFI值的差异性。运用Bonferroni检验校正不同时间节点下多重检验的阈值结果。结果急性周围神经损伤后第1周,所有组大鼠的FA值显著下降,随后逐渐升高,直至第4周恢复至接近正常水平;而RD值在手术后1周内显著上升,随后逐渐下降,同样于第4周时恢复至接近正常水平。电针组和干细胞组大鼠在术后不同时间点(2~4周)的恢复均优于对照组,且电针组的恢复最为显著(P<0.001)。T2WI-FS显示在术后的1、2、4周,电针组及干细胞组大鼠与对照组大鼠相比在神经水肿消退速度方面具有显著差异(P<0.001);神经直径与T2值在手术后1周内显著升高,此后逐渐下降,在第4周时恢复至接近正常水平;甲苯胺蓝染色与SPRR1A轴突染色均指向电针组的神经纤维连续性恢复最快,其次是干细胞组。结论电针在急性周围神经损伤疾病中的治疗效果可与干细胞移植治疗相当,并在减轻水肿及炎性反应方面极具优势。DTI参数FA和RD值是髓鞘完整性的成像标志物。

Objective:To evaluate the therapeutic effect of electroacupuncture and stem cell transplantation on acute peripheral nerve injury by magnetic resonance diffusion tensor imaging(DTI).Materials and Methods:A total of 48 adult SD rats with successful modeling were randomly divided into an electroacupuncture(EA)group,a stem cell group and a control group,16 rats in each group.The rats in the EA group were treated with EA at Huantiao(GB 30)and Zusanli(ST 36).Rats in the stem cell group were microinjected with 3μL saline suspension containing about 5×105 bone marrow mesenchymal stem cells under the epineurium at the injury site.The control group was microinjected with the same volume of saline.Multi-parametric magnetic resonance imaging[DTI and T2-weighted fat saturation(T2WI-FS)],histological evaluation and immunohistochemical analysis were used to monitor the changes of nerve structure(including nerve diameter,myelin sheath thickness and morphological changes,axonal continuity recovery).Somatic functional index(SFI)and gait trajectory analysis were used to evaluate the motor function of sciatic nerve.The differences of T2 value,DTI parameters[fractional anisotropy(FA),radial diffusivity(RD)]and SFI values among different experimental groups were analyzed by repeated measures one-way ANOVA.Bonferroni test was used to correct the threshold results of multiple testing at different time points.Results:At the first week after acute peripheral nerve injury,the FA value of all groups decreased significantly,and then gradually increased,and returned to the normal level at the fourth week.The mean value of RD increased significantly within 1 week after surgery,then gradually decreased,and returned to the normal level at the 4th week.The recovery of rats in the EA group and the stem cell group was better than that in the control group at different time points(2-4 weeks)after operation,and the recovery in the EA group was the most significant(P<0.001).T2WI-FS showed that at 1,2,and 4 weeks after operation,the EA group and the stem cell group had significant differences in the speed of nerve edema regression compared with the control group(P<0.001).The nerve diameter and T2 value increased significantly in the first week after operation,then gradually decreased,and returned to the normal level in the fourth week.Toluidine blue staining and SPRR1A axonal staining indicated that the nerve fiber continuity in the EA group recovered most rapidly,followed by the stem cell group.Conclusions:The therapeutic effect of electroacupuncture on acute peripheral nerve injury is similar to that of stem cell transplantation,and it has great advantages in reducing edema and inflammatory response.DTI parameters FA and RD values are imaging markers of myelin integrity.