【摘要】 目的 探讨MRI对比剂Gd-DTDAS在多发性硬化（multiple sclerosis, MS）大鼠髓鞘损伤模型中的应用价值。材料与方法细胞实验中，将少突胶质细胞前体细胞（oligodendrocyte precursor cells, OLN-93）随机分为对照组2(n=3)和溶血磷脂酰胆碱（lysophosphatidylcholine, LPC）组（n=3）,LPC组细胞置于无菌共聚焦培养皿中与1 mL 800μM LPC溶液共孵育30 min。通过噻唑蓝比色法（methyl thiazolyl tetrazolium, MTT）评价细胞毒性，计算OLN-93与Gd-DTDAS共孵育24 h后的吸光度和存活率；细胞摄取实验中，对照组2和LPC组对比，定量两组细胞对Gd-DTDAS的摄取值以及相应荧光强度的变化。动物实验中，将6～8周龄SD大鼠随机分为对照组（n=12）与实验组（n=18），实验组大鼠左侧胼胝体注射1%LPC溶液（1%LPC溶于PBS）。造模后（1、3、7 d）进行行为学观察，并在注射后7天进行T1WI及T2WI序列扫描。根据MRI异常信号部位进行大鼠脑组织Gd-DTDAS染色（n=6）以及浸泡（n=6），评估Gd-DTDAS与髓鞘部位的结合情况，其中，染色实验分组命名为对照组3与实验组3，浸泡实验分组命名为对照组4与实验组4；通过尾静脉注射Gd-DTDAS,MR评估实验组（n=6）注射Gd-DTDAS前后大脑髓鞘变化。结果 细胞毒性实验中，当Gd-DTDAS浓度增加到400μM时，OLN-93细胞的存活率约为95%，细胞存活率差异无统计学意义（t=4.20,P>0.05）。细胞摄取实验中，两组细胞均能摄取Gd-DTDAS,LPC组摄取量显著低于对照组2，差异具有统计学意义（t=31.75,P<0.01）。动物体外实验中，与对照组3比较，Gd-DTDAS染色的实验组3脑组织切片荧光强度显著下降，差异有统计学意义（U=9,P<0.01）;Gd-DTDAS浸泡中，对照组4(n=6)与实验组4(n=6)脑组织切片浸泡后MRI分辨率显著升高，差异有统计学意义（对照组4,t=8.76,P<0.01）（实验组4,t=2.89,P<0.01）。体内实验中，与尾静脉注射前比较，注射后胼胝体区域MRI T1maps弛豫性显著降低（t=14.46,P<0.01）。结论 髓鞘探针Gd-DTDAS能够更好地结合髓磷脂丰富的区域，髓鞘靶向MRI显像更佳，能特异性显示多发性硬化髓鞘损伤部位。更多还原

【Abstract】 Objective: To investigate the application value of MRI contrast agent Gd-DTDAS in multiple sclerosis(MS) rat myelin injury model. Materials and Methods: In cell experiments, oligodendrocyte precursor cells(OLN-93) were randomly divided into control group 2(n=3) and lysophosphatidylcholine(LPC) group(n=3), and the cells of LPC group were incubated with 1 mL of 800 μM LPC in a sterile confocal dish for 30 min. Cytotoxicity was evaluated by methyl thiazolyl tetrazolium(MTT), and the absorbance and survival rate of OLN-93 after incubation with Gd-DTDAS for 24 h were calculated. In the uptake experiment, the control group 2 and the LPC group were compared to quantify the uptake value of Gd-DTDAS and the corresponding fluorescence intensity of the two groups. In animal experiments, 6-8 week-old SD rats were randomly divided into control group(n=12) and experimental group(n=18), and the left corpus callosum of rats in the experimental group was injected with 1% LPC solution(1% LPC dissolved in PBS). After molding,behavioral observation was performed(1, 3, 7 d), and T1WI and T2WI sequence scanning were performed 7 d after injecting.Gd-DTDAS staining(n=6) and soaking(n=6) of rat brain tissue were performed according to the MRI abnormal signal site to evaluate the binding of Gd-DTDAS to the myelin site. Among them, the staining experiment was named as control group 3 and experimental group 3, while the soaking experiment group was named as control group 4 and experimental group 4. Gd-DTDAS was injected by tail vein, MRI assessed cerebral myelin sheath changes before and after Gd-DTDAS injection in the experiment group(n=6). Results: In the cytotoxicity experiment, when the concentration of Gd-DTDAS increased to 400 μM, the survival rate of OLN-93 cells was about 95%,and there was no significant difference in cell survival between concentrations(t=4.20, P>0.05). In the cell uptake experiment, both groups of cells could uptake Gd-DTDAS, and the uptake of LPC group was significantly lower than that of the control group 2, and the difference was statistically significant(t=31.75, P<0.01). In vitro experiments, compared with the control group 3, the fluorescence intensity of brain tissue sections in the experiment 3 group stained with Gd-DTDAS decreased significantly, and the difference was statistically significant(U=9, P<0.01). After immersion of brain tissue slices in Gd-DTDAS, the MRI resolution significantly increased in both the control group 4(n=3) and the experiment group 4(n=6), with statistically significant differences(control group 4, t =8.76, P<0.01; experiment group 4, t =2.89, P<0.01). In vivo experiments, MRI T1maps relaxation in the medullary region was significantly reduced after injection compared with before tail vein injection(t =14.46, P<0.01). Conclusions: The myelin probe Gd-DTDAS can better bind to myelin-rich regions, and the myelin sheath can be better targeted for MRI, and can specifically show the damage site of myelin sheath in multiple sclerosis.更多还原