纳米粒子介导血管内皮生长因子基因治疗兔心肌缺血的疗效

目的观察纳米粒子介导血管内皮生长因子(VEGF)基因转染的可行性,了解心肌缺血动物模型经心肌直接注射VEGF基因纳米粒子后新生血管以及心功能改善情况。方法应用聚乳酸聚乙醇酸共聚物(PLGA)和聚乙烯醇(PVA)包载VEGF165基因质粒,制备纳米级粒子混合物,检测其载药量、体外释放情况及粒径;培养乳鼠心肌细胞,转染VEGF165基因纳米粒子(VEGF纳米粒子),应用RT-PCR法检测VEGF mRNA水平,ELISA法检测VEGF蛋白表达水平;将VEGF纳米粒子悬浮液注射至活体家兔心肌内,96h后心肌注射部位取材,电镜观察其向心肌组织内传递基因的可行性;建造兔心肌缺血模型,分别将VEGF纳米粒子(12只)、VEGF165裸质粒(12只)或生理盐水(对照组,8只)注射至缺血部位心肌,1个月后心脏超声监测,然后处死,组织学切片观察心肌组织中毛细血管生成情况。结果制备的纳米粒子载药量为1·87%,粒径为50~300nm;RT-PCR和ELISA结果提示纳米粒子可将目的基因转移至培养的心肌细胞中;体内实验显示心肌细胞胞质内及胞核内可见大量被吞噬的纳米粒子;术后1个月超声检查显示,VEGF纳米粒子组室壁运动幅度(1·87mm±0·32mm)、左室射血分数(60%±10%)较裸质粒组(1·59mm±0·24mm,50%±6%)及对照组(0·93mm±0·40mm,40%±8%)改善更加明显,各组之间差异均有统计学意义(均P<0·05);组织学检查显示,在100倍光镜视野下心肌内毛细血管数VEGF纳米粒子组(57个±12个)明显高于裸质粒组(41个±14个)及对照组(24个±8个),各组之间差异有统计学意义(均P<0·05)。结论纳米粒子可作为VEGF基因向心肌组织转运的载体,在兔心肌缺血模型经心肌直接注射VEGF165基因纳米粒子,能够促进心肌内毛细血管新生,达到改善心功能的目的。

Effect of nanoparticle with vascular endothelial growth factor gene transferred into ischemic myocardium: experiment with rabbits

OBJECTIVE: To evaluate the possibility and efficiency of nanoparticle as a new vector in vascular endothelial growth factor (VEGF) gene transference, and investigate the efficacy of direct gene transfer of nanoparticle with VEGF(165) gene into ischemic myocardium. METHODS: Nanoparticle-VEGF (Np/VEGF) complex was prepared with poly (D, L-lactide-co-glycolide) (PLGA) loading VEGF(165) gene and the envelopment efficiency and size of the complex were determined. The Np/VEGF was transfected into the cultured myocardial cells, RT-PCR and ELISA were used to evaluate the transfection of VEGF. Suspension of Np/VEGF was injected into the myocardial tissue of 4 rabbits. 96 hours after operation myocardial tissue was obtained, made into sections, and observed with electron microscope. New Zealand White rabbits underwent thoracotomy followed by ligation of left anterior descending coronary artery to establish ischemic models. The New Zealand White rabbits were divided into 3 groups: Np/VEGF group (n = 12, nanoparticle with VEGF(165) were injected into the cordial myocardium), blank plasmid group (n = 12, injected with blank VEGF(165) plasmid), and control group (n = 8, injected with normal saline). Ultrasonography and immunohistochemistry with factor VIII related antigen were conducted to evaluate the cardiac function and the collateral circulation of the occluded artery. One month later the rabbits were killed to observe the vascularization of capillaries in the ischemic myocardium. RESULTS: The envelopment efficiency of the Np/VEGF complex thus prepared, 50 - 300 nm in size, were 1.87% y. RT-PCR and ELISA showed that VEGF gene had been successfully transfected into myocardial cells by the nanoparticles. A great number of nanoparticles were observed in the myocardial cytoplasm and nuclei. One month after operation, the ventricular wall motor amplitude of the Np/VEGF group was 1.87 mm +/- 0.32 mm, significantly larger than those of the blank plasmid group (1.59 mm +/- 0.24 mm, P < 0.05) and control group (0.93 mm +/- 0.40 mm, P < 0.05); and the left ventricular ejection fraction of the Np/VEGF group was 60% +/- 10%, significantly higher than those of the blank plasmid group (50% +/- 6%, P < 0.05) and control group (40% +/- 8%, P < 0.05). The capillary density at low power field (x 100) of the Np/VEGF group was 57 +/- 12, significantly higher than those of the VEGF group (41 +/- 14) and control group (24 +/- 8). CONCLUSION: Nanoparticle can act as a vector to transfect specific gene in vitro and in vivo. Direct gene transfer of nanoparticle with DNA encoding VEGF into the ischemic rabbit myocardium can increase capillary number; therefore it may be a novel therapeutic approach for myocardial ischemia.