小鼠神经胶质瘤单次高剂量放射治疗脑损伤评估

Evaluation of radiation-induced brain injury after signal high-dose radiotherapy for mouse glioma

目的神经胶质瘤是最常见的中枢神经系统恶性肿瘤,对现有治疗方法反应不佳,预后差。本研究探讨单次高剂量放疗对神经胶质瘤的疗效和对神经组织的损伤情况。方法 12只健康重症联合免疫缺陷(severe combined immunodeficiency,SCID)小鼠按随机数表法分为9L胶质母细胞瘤模型组(n=6)和颅窗模型组(n=6),均接受单次高剂量放疗(60Gy)。利用MR监测肿瘤生长及放疗引起的脑组织结构改变,通过钙指示剂和双光子显微镜观察放疗前后小鼠清醒状态下的神经活动,采用免疫荧光染色及HE染色明确放疗后脑组织病理学改变。结果小鼠颅内9L胶质瘤于T2加权像(T2weighted image,T2WI)和增强T1加权像(T1weighted image,T1WI)上呈现高信号。放疗后1周,MR示胶质瘤体积显著缩小,2周后肿瘤不再显影。6周后,T2WI及增强T1WI均未见脑实质内异常信号,放疗侧和对侧脑组织T2WI信号强度分别为0.933±0.057和0.870±0.078,差异无统计学意义,t=1.333,P=0.240;放疗侧和对侧脑组织T1WI-Gd增强成像信号强度分别为1.113±0.108和1.217±0.072,差异无统计学意义,t=1.735,P=0.143。但放疗侧脑室(0.367±0.027)较对侧(0.937±0.043)缩小,差异有统计学意义,t=24.680,P<0.001。双光子显微镜下发现,放疗前及放疗后6周照射脑区的神经元均具有神经活动。HE染色未见脑组织形态学改变。免疫荧光染色显示,双侧皮层神经元形态正常,放疗侧和健侧神经元数目分别为199.3±11.860和197.7±9.374,差异无统计学意义,t=0.387,P=0.715;但放疗侧活化的星胶质细胞数(43.33±9.245)高于对侧(10.00±1.673),差异有统计学意义,t=8.537,P<0.001。结论单次高剂量放疗可根治小鼠神经胶质母细胞瘤,肿瘤根除后4周出现星形胶质细胞增生及脑室缩小等放射性损伤,在此前具有较长的干预时间窗以阻止神经损伤的进程。

OBJECTIVE Glioma is the most common malignant tumor in the central nervous system with poor prognosis.The study aimed to observe the efficacy of single high-dose radiotherapy on glioma and radiation-induced neural injury.METHODS Twelve SCID mice were divided into 9 Lglioblastoma-bearing group and cranial window group(n=6/group),followed by single high-dose radiotherapy(60 Gy).MRI was performed to monitor tumor growth and the cerebral structure changes induced by radiation.Calcium indicators and two-photon microscopy were applied pre-and post-radiation to image neuronal activity in awake mice.The pathological changes of brain tissue after radiotherapy were investigated by HE and immunofluorescent staining.RESULTS 9 L glioblastoma displayed hyperintensities on T2-weighted images(T2 WI)and enhanced T1-weighted images(T1 WI).One week after radiotherapy,the tumor shrunk greatly and was invisible 2 weeks later on MRI.Six weeks post radiation,T2 WI and T1 WI enhancement did not show visible abnormalities in the brain parenchyma,and the difference of signal intensity in the cortex between two hemispheres was not statistically significant on T2 WI(0.933±0.057,0.870±0.078,t=1.333,P=0.240)and T1 WI enhancement(1.113±0.108,1.217±0.072,t=1.735,P=0.143).However,the ventricular size on irradiated side decreased significantly versus the contralateral side(0.367±0.027,0.937±0.043,t=24.680,P<0.001).Two-photon microscopy revealed individual neuronal activities in the targeted area both pre-and 6-week-post-radiation.No brain morphological changes were observed by HE staining.Immunofluorescent staining showed that there were no morphological changes of neurons and neuronal loss(199.3±11.860,197.7±9.374,t=0.387,P=0.715),but the numbers of active astrocytes were increase in irradiated hemisphere compared with the contralateral side(43.33±9.245,10.00±1.673,t=8.537,P<0.001).CONCLUSIONS Single highdose radiotherapy achieves eradication of mouse glioblastoma.Radiative damage such as astrocytosis and ventricle shrinkage occurred 4 weeks after the tumor was eradicated,which offers an interventional time-window to prevent and repair brain damage.