Evaluating the therapeutic efficacy of vascular endothelium growth factor plasmid in treating dog cerebral infarction with diffusion-weighted magnetic resonance imaging / 中国组织工程研究

ABSTRACT

BACKGROUND: Vascular endothelium growth factor (VEGF) is an endothelium mitogen and angiogenic factor with strong potential during recovery from cerebral infarction (CI). Can such therapeutic effect be detected with magnetic resonance diffusion imaging?OBJECTIVE: To study the therapeutic efficacy of VEGF plasmid in treating focal cerebral infarction in a dog experimental model with the aid of diffusion- and hemodynamic-weighted magnetic resonance imaging (MRI),with the morphological results compared with those of immunohistochemical examination.DESIGN: Completely randomized controlled, double blind evaluation,analysis of variance, Pearson correlation analysis, follow-up for 2 weeks.SETTING: Department of Medical Iconography, the Second Affiliated Hospital of Hebei Medical University.MATERIALS This study was carried out at the Department of Medical Iconography, the Second Affiliated Hospital of Hebei Medical University,between April 2001 and March 2002. Totally 18 healthy adult dogs weighing 10-15 kg were randomly divided into control group and experiment group with half in each.METHODS: All dogs were subjected to femoral intubation and then made into CI model by the occlusion of middle cerebral artery with an embolus injected through the internal carotid artery. Dogs in control group were put to death at postoperative 24 hours, 1 week and 2 weeks with three at each time point, while four dogs in experiment group were put to death at postoperative 1 week and five at 2 weeks. Dogs in experiment group received microinjection of 0.5 mL fluid containing pcD2/hVEGF121 (500-600 μg)instantly after operation, which was replaced with physical saline of the same volume at the same time point in control group. Then they were subjected to MRI scanning once an hour for 4 times, with the sequence of T1WI, T2WI, 3D-TOFMRA, DWI and CET1WI, which was repeated at postoperative 24 hours, 3 days, 1 week and 2 weeks. Based on the MR images, pathological focuses were selected for morphological observation of cells with the aid of HE staining, and CD34 IHC staining was used for counting micrangium, as well as VEGF staining for VEGF positive cells.Then the apparent distribution coefficient (ADC) was calculated, and the differences between different time points and groups were analyzed by analysis of variance. The number of capillaries and VEGF positive cells of each high-power field was counted, with the results compared with those of MR scanning so as to explore the correlation between MR signal changes and IHC results.MAIN OUTCOME MEASURES: ① The number of capillaries and VEGF positive cells in each high-power field was counted at postoperative 24 hours, 1 week and 2 weeks; ② MR images of each group.RESULTS: Data of the 18 dogs entered the final analysis. ① Diffusionweighted imaging (DWI) showed higher signals at infarctional region at postoperative 1 hour, which became strengthened as time went by. ②ADC decreased to (5.61 ±1.39) mm2/s at postoperative 3-4 hours, about 43% lower than that of the opposite hemisphere [(9.85±2.04) mm2/s]. It resumed to (9.83±1.11) mm2/s, but was still lower than the normal level.③ The subsequent MR scanning proved that ADC ratio presented an increasing tendency in contrast with the decreasing tendency at super-acute stage. The increment was even more marked in control group and the difference was significant at postoperative 2 weeks (P=0.032, 0.006). ④ The number of capillary positive cells on the affected side in experiment group was significantly higher than that in control group at postoperative 2 weeks [(28.80±3.29)/field, (20.70±4.47)/field, (P ＜ 0.01)]. ⑤ The number of VEGF positive cells on the affected side in experiment group was significantly higher than that in control group at postoperative 1 and 2weeks [(64.20±9.40)/field, (51.90±5.74)/filed; (72.70±6.98)/filed,(58.40±6.35)/field, (P ＜ 0.01)].⑥ The results of MR scanning and IHC were subjected to correlation analysis and revealed that ADC ratio was closely correlated with the number of capillary positive cells, with Pearson correlation coefficient being 0.679 (P ＜ 0.01). Moreover, the number of capillaries and the number of VEGF positive cells were significantly correlated (r=0.668, P ＜ 0.01).CONCLUSION:Morphological observation and IHC revealed that both the local capillaries and VEGF protein content increased markedly in timedependant manner due to VEGF plasmid gene therapy.Meanwhile,the change of ADC ratio was found to be closely correlated with the number of VEGF positive cells and the number of capillaries.