目的: 是研究不同剂量新型叶绿素光敏剂HPPH光动力学疗法治疗大鼠C6脑胶质细胞移植瘤模型, 以磁共振波谱技术(MRS)无创观察不同时间的变化、评价疗效及选择光敏剂HPPH最佳剂量并与常规光敏剂血卟啉衍化物(HPD)光动力学治疗及对照组作对比。方法: 建立大鼠C6脑胶质细胞瘤模型, 设立对照组(空白对照组、单注射HPPH0.45 mg/kg组、单注射HPD5 mg/kg组、单波长667nm激光照射组、单波长630 nm激光照射组)、HPPH-PDT各组(HPPH0.15、0.30、0.45 mg/kg组)、HPD-PDT5 mg/kg组。单注射HPPH组、HPPH-PDT组和单注HPD组、HPD-PDT组自尾静脉推注入光敏剂, 光动力学治疗组注光敏剂后18小时进行激光照射.HPPH-PDT各组和单667 nm激光照射组肿瘤以波长667nm的半导体激光照射, 功率密度200 mW/cm2, 每光斑照射20 min, 能量密度为240 J/cm2；HPD-PDT组及单630 nm激光照射组肿瘤以波长630nm的半导体激光照射, 功率密度200 mW/cm2, 每光斑照射20min, 能量密度为240 J/cm2。以磁共振平扫、增强扫描及磁共振波谱技术(MRS)观察光动力学治疗组及对照组肿瘤不同时间的变化,光动力学治疗前、治疗后7、14天(P0、P7、P14天水)；接种后第7、14、21天；(T7、T14、T21天)。于PDT后14天或肿瘤生长第21天磁共振扫描后处死鼠, 取脑组织作病理检查。结果: 本文观察大鼠C6脑胶质瘤模型接种不同时间段波谱cho/NAA均值, 正常脑cho/NAA均值在第1、7、14、21天测定在0.5左右, 而接种后的大鼠C6脑胶质瘤及未光动力学治疗各组7、14、21天测定波谱cho/NAA均值为5.532±4.066～5.574±3.382、6.488±2.169～6.744±3.685、8.684±5.42～8.938±4.08, 随着肿瘤的长大该均值在不断加大。正常脑与移植瘤未光动力学治疗各对照组波谱 cho/NAA值T-检验, P值小于0.05或0.001有显著或非常显著差异。而移植瘤未光动力学治疗各对照组、各时间组间P＞0.05,各组间无显著差异。光动力学治疗组cho/NAA均值HPPH 0.30、0.45、0.15 mg/kg-PDT、HPD-PDT为0.832±0.334、0.818±0.166、6.912±3.81、7.456±3.33,前两组明显小于后两组, 疗效优于后两组, 后两组, 前者小于后者, 疗效又优于后者。总的HPPH-PDT疗效优于HPD-PDT。T检验前两组HPPH0.30、0.45 mg/kg-PDT组间比P＞0.05无显者差别, 与正常脑比P＞0.05无显著差别, 且接近正常脑值, 与对照未治疗组比P值＜0.05有显著差别, 与后两组HPPH0.15 mg/kg-PDT、HPD-PDT比P值＜0.05有显著差异, 后两组间比P＞0.05无显者差别。以磁共振增强扫描测定各组肿瘤体积, P14/P0(光动力学治疗后14, 与光动力学治疗前)HPPH0.15、0.30、0.45 mg/kg-PDT组、HPD5 mg/kg-PDT组值为4.43±4.8、0.37±0.25、0.71±0.42、8.31±1.56；对照组T21/T7(肿瘤生长21天与肿瘤生长第7天比)单注药HPPH0.45 mg/kg组、单注药HPD5 mg/kg组、单激光670 nm照射组、单激光630 nm照射组、未治疗肿瘤组为17.01±0.36、16.66±0.31、18.37±0.47、17.66±0.04、20.24±1.75。第21天病理表现, 正常脑组织仅见神经元细胞及胶质细胞量；而接种C6胶质细胞瘤后大鼠脑可见大片密集成巢状生长, 色深、大小不一、有核分裂的肿瘤细胞, 随着肿瘤生长时间的增加, 肿瘤细胞的密度加大。未光动力学治疗组的病理表现与上相同。光动力治疗后可见肿瘤细胞变性、色变淡、细胞密度减少, 脑组织水肿及毛细血管扩张, 程度与光敏剂HPPH的剂量有关, HPPH0.15 mg/kg-PDT较差一些、而HPPH0.3、0.45 mg/kg-PDT 较明显、有的只有少量的肿瘤细胞, 仅可见正常脑神经元细胞及胶质细胞；而HPD-PDT后的脑肿瘤细胞变性程度较HPPH-PDT更差一些, 标本中仍可见较多的肿瘤细胞。结论: 磁共振平扫、增强、MRS技术对大鼠脑组织进行扫描分析, 能在无创情况下动态观察接种C6脑胶质瘤后及光动力学治疗后大鼠脑组织内胶质瘤的生长情况, 能了解病变的能量代谢、生化改变, 并对特定化合物进行定量分析。HPPH-PDT能治疗大鼠C6脑胶质瘤移植瘤, 剂量以HPPH0.30 mg/kg较佳。HPPH-PDT疗效优于HPD-PDT。

Objective: The aim is to use magnetic resonance spectroscopy(MRS)to investigate the efficacy of the photodynamic therapy(PDT)with different doses of the photosensitizer 2-［1-hexyloxyethyl］-2-devinyl pyropheophorbide-alpha(HPPH )on the C6 glioma in the rat, in which the optimal dose of the HPPH will be selected and the efficacy will be compared with that of the PDT with the hematoporphyrin derivative(HPD).Methods: After setting up the C6 glioma model in the rat, the animals were divided into control groups (blank group, HPPH only(0.45 mg/kg)group, HPD only(5 mg/kg)group, 667 nm laser light only group, and 630 nm laser light only group), HPPH-PDT groups(HPPH0.15, 0.30, and 0.45 mg/kg groups), and HPD-PDT(5 mg/kg))group. The photosensitizers were injected into the rats via the tail veins. 18 h after the injection of the photosensitizers, while 667 nm laser beam was used to irradiate the tumors in the groups of HPPH-PDT and the group of 667 nm laser light only, the tumors of the HPD-PDT group and 630 nm laser light only group were treated with 630 nm laser beam at a laser intensity of 200 mW/cm2 and an energy density of 240 J/cm2 for 20 min per photo spot. The magnetic resonance imaging (MRI) and MRS were used to observe the tumor changes in the PDT groups and control groups before and 7 and 14 days after the PDT(P0, P7, P14), that is, 7, 14, and 21 days after tumor implantation(T7, T14, T21). The rats were sacrificed for pathological examination 14 days after the PDT or on 21st day after tumor implantation. Results: The choline/ n-acetylaspartate (Cho/NAA) value of the MRS was measured. It was approximately 0.5 in the normal rat brain, but the values were significantly increased to 5.532±4.066～5.574±3.382, 6.488±2.169～6.744±3.685, and 8.684±5.42～8.938±4.08 on day 7, 14, and 21 after glioma cell implantation, respectively(P＜0.05 or 0.01), which was elevated with the tumor growth. There are no significant difference among the tumor groups(P ＞0.05). After the PDT, the Cho/NAA values of 0.832±0.334, 0.818±0.166, 6.912±3.81, and 7.456±3.33 were noted in the HPPH 0.3, 0.45, and 0.15 mg/kg-PDT groups and the HPD-PDT group, respectively. As compared to that in the HPPH 0.15 mg/kg-PDT group, HPD-PDT group, or untreated groups, the values in the HPPH 0.3 and 0.45 mg/kg-PDT groups were dramatically greater(P＜0.05). The enhanced MRI was used to measure the tumor volumes, and the ratios of P14/P0 in the HPPH 0.15, 0.3, and 0.45 mg/kg-PDT groups, HPD5 mg/kg-PDT group were 4.43±4.8, 0.37±0.25,0.71±0.42, and 8.31±1.56, respectively. The T21/T7 values were 17.01±0.36,16.66±0.31,18.37±0.47, 17.66±0.04, and 20.24±1.75 in the HPPH only(0.45g/kg)group, HPD only(5 g/kg)group, 667 nm laser light only group, 630 nm laser light only group, and untreated group, respectively. While the normal brain showed a normal structure consisting of neurons and glia cells, the tumor cells grew in nest pattern and showed different sizes and nuclear division on day 21 after C6 glioma implantation. The density of the tumor cells was increased with the tumor growth. After the PDT, degenerated cells, density-reduced tumor, edema, and enlarged capillary were noted, which was related to the HPPH dose. These changes were more obvious in the HPPH 0.30 mg/kg and 0.45 mg/kg-PDT groups than the one in the HPPH 0.15 mg/kg group. The degeneration of the tumor cells in the HPD-PDT was less than that in the HPPH-PDT.Conclusions: The MRI, enhanced MRI, and MRS can be used to observe the growth of the C6 glioma in the rat after tumor implantation and the PDT, evaluate the changes of energy metabolism and biochemistry, and do quantitative analyses. Moreover, the HPPH-PDT is an efficient approach to treat C6 glioma, which is better than the HPD-PDT. The optimal dose of the HPPH is 0.3 mg/mL.