光、磁分子探针在脑组织间隙内的扩散分布规律

Diffusion of fluorescent and magnetic molecular probes in brain interstitial space

目的:对比荧光分子探针四甲基罗丹明-葡聚糖(dextran-tetramethylrhodamine,DT)和荧光黄(lucifer yellow CH,LY)、磁性分子探针钆-二乙三胺五乙酸(gadolinium-diethylene triamine pentaacetic acid,Gd-DTPA)在多孔介质中的动态扩散分布规律,筛选合适的荧光分子探针用于大鼠脑组织间隙(interstitial space,ISS)光学成像。方法:琼脂糖凝胶分为DT组、LY组、Gd-DTPA组,分别导入相应分子探针,应用激光扫描共聚焦显微镜分别动态观察DT、LY在琼脂糖凝胶内的扩散分布,与磁共振成像显示的Gd-DTPA在琼脂糖凝胶内的动态扩散过程进行比较。LY分别导入18只大鼠尾状核,对不同时间点离体脑切片进行荧光成像,其成像数据与相应导入Gd-DTPA的大鼠的磁共振在体检测成像数据进行对比。结果:DT、LY及Gd-DTPA在琼脂糖凝胶中的扩散分布均表现为各向同性,平均扩散分布速率分别为:(0.07±0.02)×10-2mm2/s、(1.54±0.47)×10-2mm2/s、(1.45±0.50)×10-2mm2/s,DT与LY、DT与Gd-DTPA间差异均有统计学意义(ANOVA,F=367.15,P<0.001;Post-Hoc LSD,P<0.001),LY与Gd-DTPA间差异无统计学意义(Post-Hoc LSD,P=0.091)。重复测量方差分析比较分子探针的扩散分布面积随时间变化的趋势:DT与LY、DT与Gd-DTPA间的变化规律差异均有统计学意义(Bonferroni校正,α=0.0125,P<0.001),LY与Gd-DTPA间差异无统计学意义(Bonferroni校正,α=0.0125,P=0.203)。LY与Gd-DTPA在大鼠尾状核ISS内分布随时间变化呈各向异性,均表现为指向同侧皮层区的单方向楔形扩散,平均扩散分布速率分别为(1.03±0.29)×10-3mm2/s和(0.81±0.27)×10-3mm2/s,t=0.759,P=0.490;信号衰减半衰期分别为(2.58±0.04)h和(2.46±0.10)h,t=2.025,P=0.113。LY与Gd-DTPA间扩散分布面积比率在0.5、1、2、3、7 h差异无统计学意义(t=2.249,P=0.088;t=2.582,P=0.061;t=1.966,P=0.121;t=0.132,P=0.674;t=0.032,P=0.976),在11 h差异有统计学意义(t=2.917,P=0.043)。结论:LY与Gd-DTPA在多孔介质内的扩散分布规律一致,是ISS荧光成像的适用分子探针,可用于脑ISS的微观、宏观、离体检测。

Objective： To compare the diffusion properties of fluorescent probes dextran-tetramethylrhodamine（ DT） and lucifer yellow CH（ LY） and magnetic probe gadolinium-diethylene triamine pentaacetic acid（ Gd-DTPA） in porous media and to screen out a suitable fluorescent probe for optical imaging of brain interstitial space（ ISS）. Methods： Agarose gels sample were divided into DT group,LY group and Gd-DTPA group,and the corresponding molecular probes were imported in each group. The dynamic diffusions of DT and LY in agarose gels at different time points（ 15,30,45,60,90,and 120 min） were scanned with laser scanning confocal microscope,the dynamic diffusion of Gd-DTPA was imaged with magnetic resonance imaging. The average diffusion speed of LY were demonstrated to be consistent with those of Gd-DTPA. The LY was introduced into caudate putamen of 18 rats,respectively,the diffusion of LY in the sequential slices of rat brain at different time points（ 0. 5,1,2,3,7,11 h） were scanned,and the results were compared with those of rats＇ brain with Gd-DTPA imported and imaged in vivo with magnetic resonance imaging. Results： The diffusions of the three probes were isotropic in the agarose gels,and the average diffusion speeds of DT,LY and Gd-DTPA were：（ 0. 07 ± 0. 02） × 10^-2mm^2/ s,（ 1. 54 ± 0. 47） × 10^-2mm^2/ s,（ 1. 45 ± 0. 50） × 10^-2mm^2/ s,respectively. The speed of DT was more slower than both LY and Gd-DTPA（ ANOVA,F = 367. 15,P〈0. 001; Post-Hoc LSD,P〈0. 001）,and there was no significant difference between the speeds of LY and Gd-DTPA（ Post-Hoc LSD,P =0. 091）. The variation tendency of diffusion area of DT was different with both that of LY and that of GdDTPA（ Bonferroni correction,α = 0. 0125,P〈0. 001）,and there was no significant difference between LY and Gd-DTPA（ Bonferroni correction,α = 0. 0125,P = 0. 203）,in analysis by repeated measures data of ANOVA. The diffusions of LY and Gd-DTPA were anisotropy in rat caudate putamen,and the average diffusion speeds of LY and Gd-DTPA were：（ 1. 03 ± 0. 29） × 10^-3mm^2/ s,（ 0. 81 ± 0. 27） ×10^-3mm^2/ s,respectively,no significant difference was demonstrated（ t = 0. 759,P = 0. 490）; half-time of single intensity of LY and Gd-DTPA was（ 2. 58 ± 0. 04） h,（ 2. 46 ± 0. 10） h,respectively,no significant difference was found（ t = 2. 025,P = 0. 113）. The diffusion area ratios between LY and Gd-DTPA in rat caudate putamen was not statistically different at hours 0. 5,1,2,3 and 7（ t = 2. 249,P = 0. 088;t = 2. 582,P = 0. 061; t = 1. 966,P = 0. 121; t = 0. 132,P = 0. 674; t = 0. 032,P = 0. 976）,while,a slightly difference was found at 11 h（ t = 2. 917,P = 0. 043,in analysis by t test）. Conclusion： LY present the same diffusion property with Gd-DTPA in porous media witch including agarose gels and live rat brain tissue,indicates that LY is a suitable fluorescent probe for optical imaging of brain ISS,and it can be used for microscopic,macro and in vitro measure of brain ISS.