重组腺相关病毒载体在大鼠海马内转导特征及其细胞亲嗜性

Gene Transfer Efficiencies and Cell Tropism of Recombinant Adeno-associated Virus in the Hippocampus of Adult Rat

目的 探讨3种不同血清型重组腺相关病毒（rAAV1、rAAV2和rAAV5）载体在大鼠海马内转导效率及细胞亲嗜性的差异，从而选择更加适于中枢神经系统（CNS）转基因治疗的载体。方法 雄性健康成年SD大鼠18只，随机分为3组，每组6只，分别接受立体定向注射剂量和滴度相匹配的rAAV1、rAAV2、rAAV5载体，以增强型绿色荧光蛋白（EGFP）为报告基因，于注射后8周取脑行序列冰冻切片，以荧光显微镜观察EGFP在脑内的表达情况，并以Image-Pro Plus图像处理系统自动测量表达的面积和阳性细胞数量；为确定rAAV载体在CNS中的细胞亲嗜性，以神经元核性蛋白（NeuN）和胶质纤维酸性蛋白（GFAP）免疫荧光双重标记法观察EGFP在不同类型神经细胞的表达情况。结果 各组EGFP表达呈现不同分布特征，rAAV1介导EGFP在海马CA1～CA3区绝大多数锥体细胞及齿状回的颗粒细胞中表达，rAAV2主要局限于齿状回门区的多形细胞层，rAAV5仅在CA1和CA2区锥体细胞层的少量细胞中表达。最大嘴尾侧转导距离、最大转导面积和EGFP阳性细胞计数rAAV1均显著大于rAAV2和rAAV5（P〈0．01），rAAV2和rAAV5比较，差异均无显著性（P〉0．05）。免疫荧光标记显示rAAV1既可以转导神经元，又可以转导胶质细胞；而rAAV2和rAAV5则仅可转导神经元。结论 rAAV1不仅可以比rAAV2和rAAV5转导更大的范围和细胞数量，而且具有更广的组织亲嗜性，是一种高效的转基因载体。

Objective To explore the gene transfer efficiencies and different cell tropism of recombinant adeno-associated virus 1 （rAAV1） , rAAV 2, and rAAV 5 in the hippocampus of adult rats, and select more suitable gene vectors for central nervous system （CNS） gene therapy. Methods Eighteen SD male adult rat were divided into 3 groups randomly （ n = 6 ） , with every group being injected with the titre and volume matched rAAV1, rAAV2, and rAAV5 vectors. All these vectors contained enhanced green fluorescent protein （EGFP） sequences as a reporter gene. Animals were killed after 8 weeks. The coronal cryosections of brains were processed, and the EGFP gene expression was observed with fluorescence microscopy; the expression area and the number of EGFP positive cells were automatically measured using Image-Pro Plus 4.5 software. To identify their cell tropism in the CNS, the sections were counterstained with neuronal marker neuron-specific nuclear protein （NeuN） and the astrocyte marker glial fibrillary acidic protein （GFAP） and were examined with a confocal laser scanning microscope. Results Eight weeks after adeno-associated virus gene transfer, the expression profile of EGFP demonstrated significant difference. Most of the pyramidal cell layers of CA1 to CA3 area and granular cell of dent gyrus were strongly transduced by rAAV1 ; whereas rAAV2 primarily transduced the cells of multiform layer in hilar region of the dentate gyrus; only a few pyramidal cells were transduced by rAAVS. Moreover, rAAV1 showed significantly wider distribution throughout the hippocampus, and the quantity of EGFP positive＇cells and the EGFP positive area were significantly more than those of rAAV2 and rAAV5 （P 〈0. 01 ）. The counterstaining for NeuN and GFAP showed that rAAV1 was able to transduce both neurons and glia cells, whereas rAAV2 and rAAV5 transduced the neurons only. Conclusion rAAV1 is an excellent transgene vector with higher efficiency and broader cell tropism in the CNS.