磁共振示踪法定量测量大鼠C6胶质瘤模型细胞外间隙扩散参数

Extracellular space diffusion during progression of rat C6 glioma quantificated by magnetic resonance imaging

目的应用磁共振示踪技术定量比较了不同时期的大鼠C6胶质瘤的细胞外间隙扩散参数。并对影响细胞外间隙扩散的细胞外基质成分进行了分析。方法将示踪剂钆喷酸葡胺(gadolinium-diethylene triamine pentaacetic acid,Gd-DTPA)作为示踪剂导入大鼠脑细胞外间隙内,采用磁共振示踪法动态监测示踪剂在大鼠脑内的扩散与清除,利用已建立的数学模型,计算有效扩散系数(D*),清除速率常数(k’)和半衰期(thalf-life)。对细胞外基质的主要成分,如硫酸软骨素蛋白多糖(CSPGs)、腱生蛋白C、胶原蛋白IV型进行免疫组化和蛋白质印记分析。结果与10 d C6胶质瘤相比,20 d胶质瘤有效扩散系数((6.67±1.78)×10-5mm2/s vs.(1.26±0.27)×10-4mm2/s;t=4.265;P<0.01)及清除速率常数((7.67±2.29)×10-5mm2/s)vs.(1.46±0.36)×10-4mm2/s);t=3.87;P<0.05)减小,迂曲度增大((3.99±0.57)vs.(2.83±0.29);t=4.11;P<0.01)),半衰期延长((0.86±0.23 h)vs.(1.64±0.12 h);(t=5.91;P<0.01))。20 d胶质瘤的细胞外基质的硫酸软骨素蛋白糖((0.48±0.07)vs.(0.32±0.09);t=4.663;p<0.01)、腱生蛋白-C(0.29±0.04)vs.(0.58±0.11);t=6.50;P<0.01)和胶原蛋白IV型(0.24±0.07)vs.(0.33±0.06);t=3.81;P<0.05)的含量较10 d胶质瘤明显增加。结论随C6胶质瘤进展,细胞间隙扩散参数发生变化;细胞外基质的含量影响细胞外间隙扩散;我们相信本研究有助于我们更好地认识神经胶质瘤微环境,并将为经间质途径治疗神经胶质瘤提供参考。

Objective To compare the extracellular space diffusion at different stages of rat C6-gliomas determined by MRI tracer method and analyze the influencing effect of extracellular matrix （ ECM） on the diffusion process.Methods Introducing adolinium-diethylene triaminepentaacetic acid （ Gd-DTPA） into extracellular space （ ECS） as a tracer.The diffusion parameters and half-life time were quantified according to mathematical model of diffusion.The main ECM components （ e.g. chordroitin sulfate proteoglycans （ CSPGs ） , collagen IV tenascin C ） were detected by immunohistochemical and immunoblot analysis.Results Gd-DTPA introduced into 20-day glioma in the rats diffused more slowly [（6.67 ±1.78） ×10 -5 mm2/s vs.（1.26 ±0.27） ×10-4 mm2/s; t =4.265; P〈0.01）], deriving a larger tortuosity [（3.99 ±0.57） vs.（2.83 ±0.29）;t=4.11;P〈0.01）], localized within the tumor with a smaller clearance rate [（7.67 ±2.29） ×10 -5mm2/s）vs.（1.46 ±0.36） ×10 -4mm2/s）;t=3.87;P〈0.05）, and a longer half-life time （（0.86 ±0.23 h）vs.（1.64 ±0.12 h）;（t=5.91;p〈0.01）] compared with 10-day gliomas in the rats.The increased levels of extracellular matrix of glioma were associated with different diffusion and clearance parameters of 20-day gliomas in the rats in comparision with those in the 10-day rat gliomas, in which the chordroitin sulfate proteoglycans[（0.48 ±0.07） vs.（0.32 ±0.09）;t=4.663;P〈0.01）], tenascin C [（0.29 ±0.04） vs.（0.58 ±0.11）;t =6.50;P〈0.01] and collagen IV [（0.24 ±0.07）vs.（0.33 ±0.06）;t=3.81;P〈0.05] were tested.Conclusions The ECS parameters are changed with the C6 glioma progression due to the increased ECM content.The results of our study may help us to better understanding the glioma micro-environment and provide beneficial references for the brain interstitial drug delivery to treat gliomas.