目的: 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, 无创观察磁共振波谱技术(DWI)变化、评价疗效及选择光敏剂HPPH最佳治疗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C 6脑胶质瘤移植瘤模型, 以不同剂量新型叶绿素光敏剂HPPH(0.15、0.3、0.45 mg/kg)光动力学治疗, 尾静脉注药后18 h, 以波长667 nm激光照射大鼠脑肿瘤, 照射功率密度200 mW/cm2, 照射时间20 min, 能量密度240 J/cm2, 于治疗前、治疗后7、14天(P0、P7、P14), 即肿瘤接种后第7、14、21天(T7、T14、T21天),以磁共振平扫、增强扫描及弥散技术(DWI)无创测定肿瘤大小及ADC值。并与HPD-PDT、正常脑、对照组(未治疗、单注药、单照激光)肿瘤组的ADC值作对比。最后以病理验证。结果: ADC均值正常脑在406.01±53.59-436.25±50.23间, 未治疗脑肿瘤组均值T7天、T14天、T21天分别为738±219.57、 660.65±105.32、551.37±103.58, 由于肿瘤长大, 肿瘤细胞数的增加使弥散成像ADC值下降。各单注药、单激光对照组的变化同未治疗空白组规律相似。T检验, 各未光动力学治疗对照组间比P值＞0.05无明显差异, 与正常脑比P值＜0.05有显著差异。光动力学治疗组P0组与未治疗对照组相似ADC均值在609.78～705.96之间； P7天, ADC均值由于治疗后脑组织的水肿均有升高, 以HPPH0.30、0.45 mg/kg-PDT组均值上升较多(782.2±95.6、779.01±291.1),其次HPPH 0.15 mg/kg-PDT组(765.22±110.13), HPD-PDT组降低一些(644.13±94.17)； P14天, ADC均值明显下降, 由于肿瘤细胞光动力学治疗后的凋亡、死亡,ADC均值下降, HPPH0.30、0.45 mg/kg-PDT组435.86±46.04、429.34±70.05接近正常脑值;HPPH 0.15 mg/kg-PDT组稍高619.98±93.49, HPD-PDT组550.13±94.48, 这两组由于肿瘤细胞的凋亡死亡较差, 有较多的肿瘤细胞存在, 影响弥散值, HPPH0.15mg/kg-PDT组ADC值高于HPD-PDT组, 肿瘤细胞较后者少。各组ADC值T检验, 光动力学治疗组间HPPH0.30、0.45 mg/kg-PDT两组比P＞0.05无显著差别, 上两组与HPPH0.15 mg/kg-PDT、HPD5 mg/kg-PDT, P值＜0.05有显著的差别, 与正常脑比P值＞0.05无显著差异, 与未光动力学治疗对照组比P值＜0.05有显著差别；HPPH 0.15mg/kg-PDT、HPD5 mg/kg-PDT二组间比, P值＞0.05无显著差别, 上两组与正常脑比, P值＜0.05有显著差异, 与未光动力学治疗对照组比, P值＞0.05无显著差别。以磁共振增强测定各组肿瘤体积, P14/、P0 HPPH0.15、0.30、0.45 mg/kg-PDT组、HPD5 mg/kg-PDT组均值为4.43±4.8、0.37±0.25、0.71±0.42、8.31±1.56；对照组T21/T7单注药HPPH0.45 mg/kg组, 单注药HPD5 mg/kg组、单670 nm激光照射组、单630 nm激光照射组、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. 大鼠脑接种肿瘤第21天病理表现正常脑组织仅见神经元细胞及胶质细胞；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, HPPH 0.15 mg/kg-PDT较差一些、而HPPH 0.30、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: 磁共振增强、DWI技术能在无创情况下动态观察接种C6脑胶质瘤后大鼠脑组织内胶质瘤的生长情况, 了解肿瘤细胞的凋亡情况以及肿瘤细胞密集区域, 测量肿瘤肿块大小。 HPPH-PDT能治疗大鼠C6脑胶质瘤移植瘤, 光敏剂剂量以 HPPH 0.30 mg/kg较佳。HPPH-PDT疗效优于HPD-PDT。

Objective: This study is to evaluate the efficacy of the photodynamic therapy (PDT) with different doses of the photosensitizer 2-［1-hexyloxyethyl］-2-devinyl pyropheophorbide-alpha(HPPH), by using the diffusion-weighted imaging (DWI) of magnetic resonance, 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 the one of the PDT with the hematoporphyrin derivative(HPD).Methods: In the rat C6 glioma model, different doses of the HPPH (0.15, 0.30, 0.45 mg/kg)were administrated via the veil teils of the rats. 18 h later, the C6 glioma was treated with a laser beam with 667nm wavelength at a laser intensity of 200m W/cm2 and an energy density of 240 J/cm2for 20 min. Magnetic resonance imaging(MRI)was carried out to detect the tumor sizes and the values of the apparent diffusion coefficient(ADC)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), which was then compared with the results of the HPD-PDT in normal brains and control tumor groups including untreated, photosensitizer only, and laser light only tumor groups. The pathological examination was finally performed.Results: The ADC values varied between 406.01±53.59 and 436.25±50.23 in normal brain. The average ADC values of T7, T14, and T21 in untreated tumor groups were 738±219.57, 660.65±105.32, and 551.37±103.58, respectively, which is significantly greater than that in the normal brain (P＜0.05). The values were decreased with the tumor growth and the increase in tumor cell number. There was no difference in the ADC values in untreated, photosensitizer only, and laser light only tumor groups (P＞0.05), which is similar to that of 609.78～705.96 in P0 group. On P7, the values were increased due to the edema after the treatment. The ADC values in the HPPH0.15 mg/kg and 0.45 mg/kg-PDT groups and HPPH0.15 mg/kg-PDT group were 782.2±95.6,779.01±291.1,and 765.22±110.13, respectively, while the one in HPD-PDT group was 644.13±±94.17. The ADC values were reduced on P14. The numbers in the HPPH0.15 mg/kg and 0.45 mg/kg-PDT groups were 435.86±46.04 and 429.34±70.05, respectively, which was closed to the normal value, but it was greatly elevated in the HPPH0.15 mg/kg-PDT group(619.98±93.49, P＜0.05)and the HPD-PDT group(550.13±94.48, P＜0.05)because less apoptosis caused more tumor cells remaining. The tumor sizes were measured with the MRI. The ratios of the tumor sizes on P14 to those on P0 in the HPPH0.15,0.3,0.45mg/kg-PDT groups and the HPD-PDT were respectively 4.43±4.8, 0.37±0.25, 0.71±0.42, and 8.31±1.56. The T21:T7 ratios of 17.01±0.36, 16.66±0.31,18.37±0.47, 17.66±0.04, and 20.24±1.75 were noted in the HPPH only(0.45 mg/kg),HPD only (5 mg/kg), 670 nm laser light only, 630nm laser light only, and untreated groups, 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 HPPH0.30 mg/kg and 0.45 mg/kg-PDT groups than the one in the HPPH0.15 mg/kg group. The degeneration of the tumor cells in the HPD-PDT was less than that in the HPPH-PDT. Conclusions: The enhanced MRI and DWI can be used to observe the growth of the C6 glioma, tumor cell apoptosis, and the density of tumor cells in the rat brain as well as measure the tumor size. 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 0.30 mg/mL.