构建含人胰岛素样生长因子基因腺病毒载体及在兔骨髓间充质干细胞的表达

背景:Adeasy腺病毒系统是由T.C.He等改良的基于E1和E3区缺失的重组腺病毒系统.相比传统的在真核细胞中收集和测试重组后的病毒颗粒的方法,其采用了在细菌中通过质粒同源重组的方法获得病毒颗粒,从而简化了腺病毒的构建和测试流程,而且,它能够通过整合入病毒基因组的标记基因GFP实现对转染细胞的荧光追踪,从而在近年来被广泛用作基因转染的载体.目的:用Adeasy系统构建荧光蛋白基因标记的腺病毒载体Ad-hIGF-1,并检测其在靶细胞骨髓间充质干细胞中的表达.设计:重复测量实验.单位:重庆医科大学儿科研究所.方法:实验于2004-11/2005-03在重庆医科大学儿科研究所完成.①重组腺病毒载体的构建:从pcDNA3.1-hIGF-1中扩增出截短的目的基因hIGF-1,按Ad-easy腺病毒系统同源重组的标准步骤获得重组阳性质粒pAd-hIGF-1和重组空白质粒pAd-0,电穿孔转化感受态XL-1细菌,扩增后获得重组腺病毒质粒,去内毒素质粒大抽试剂盒大量抽提质粒备转化HEK293细胞;②腺病毒包装及扩增:Pae Ⅰ酶切线性化pAd-hIGF-1和pAd-0,纯化后转染HEK293细胞,观察GFP的表达,待细胞90%以上漂浮后,冻融法裂解细胞收集第一轮病毒上清即为Ad-hIGF-1(重组目的腺病毒)和Ad-0(重组空白腺病毒),将收集病毒上清重复多次感染293细胞(乒乓交互感染)以提高病毒滴度.③骨髓间充质干细胞的培养及转染!采用通用的标准密度梯度离心法分离纯化兔MSCs于37℃、5%CO2孵箱培养,隔天换液,10 d细胞融合达70%～80%,贴壁紧密,细胞形态均一,呈典型的涡漩状排列,传代至第3代按病毒感染复数分组转染.主要观察指标:①腺病毒载体的构建及鉴定.②目的基因hIGF-1在HEK293的表达及病毒滴度.③目的基因在骨髓间充质干细胞中的表达.结果:①重组腺病毒的鉴定:从质粒pcDNA3.1-hIGF-1中顺利扩增出约400 bp大小的清晰条带,与预期相符;pMDl8-hIGF-1测序结果经Blast2.0比对与公布序列一致性99.9%(281位碱基同义突变,未影响氨基酸翻译:ggffggc-Gly);pAdtraek-CMV空载体和pAdtraek-MGF-1分别双酶切(Kpn Ⅰ和HindⅢ)鉴定正确.质粒pAdEasey-1和Ad-hIGF-1用Pac I酶切鉴定鉴定正确.证实病毒质粒同源重组成功.②荧光表达及滴度测定:重组质粒pAd-hIGF-1经Pac Ⅰ线性化后转化HEK293E细胞,48 h后在荧光显微镜下即可见GFP的表达,72h表达最强.约5-7 d后细胞出现病毒感染的特征性CPE,由此计算出腺病毒滴度为3.0× 109 pfu/mL.⑨靶细胞的感染及表达效率:病毒转染骨髓问充质干细胞24 h后观察到绿色荧光的表达,72 h左右荧光达到最强.免疫细胞化学SP法DAB染色显示在感染的骨髓间充质干细胞胞浆中有棕黄色阳性颗粒出现.SDSPAGE电泳在7.8 KD附近出现明显条带,与实际人胰岛素样生长因子-1分子量7.6 kD相符,证实转染含目的基因的重组腺病毒后的骨髓间充质干细胞中有较高量的人胰岛素样生长因子-1的表达.结论:本实验用Adeasy系统和扩增的截短型外源性基因hlGF-1构建了具有较强感染能力的腺病毒载体pAd-MGF-1,免疫细胞化学和Western Blot等方法检测证实了目的基因在靶细胞骨髓间充质干细胞得到了理想表达.

Construction of adenovirus vectors containing human insulin-like growth factor-1 gene and its expression in rabbit mesenchymal stem cells

BACKGROUND: Compared to those original viruses systems, adeasy adenovirus, a recombinant adenoviral system widely used in recent years, based on viruses with a deletion of both El and E3, reported by T.C. He in 1998, is an improved one. It simplifies the generation and production of such viruses and expedite the process of generating and testing recombinant adenoviruses using homologous recombination in bacteria rather than in eukaryotic cells. Moreover, it can be conveniently followed with the aid of green fluorescent protein encoded by EGFP gene incorporated into the viral backbone.OBJECTIVE: To construct the recombinant adenovirus and to evaluate them by transfect them to mesenchymal stem cells (MSCs)and detect the expression of target gene hlGF-I at gene and protein levels.DESIGN: Repetitive measurement wail.SETTING: The Institute of Pediatric Research, Chongqing University of Medical Science.METHODS: The study was performed at the Institute of Pediatric Research, Chongqing University of Medical Science from November 2004 to March 2005. After the amplification of truncated hlGF-1 gene from pcDNA3.l-hlGF-I by polymerase chain reaction (PCR), the gene fragment was inserted into the shuttle plasmid pAdtrack-CMV for homologous recombination with backbone plasmid pAdeasy-I in bacteria BJ5183 to get adenovirus.Ad-hlGF-1. The high titer adenovirus supernatant was obtained by repeated transducing of HEK 293 cells by adenovirus harvested after confirmation of the adenovirus structure. As target cells,MSCs were infected with adenovirus earned target gene, hIGF-1, to determine the expression of hlGF-1 gene.MAIN OUTCOME MEASURES: ① The construction of recombinant adenovirus vector;② the expression of target gene hIGF-1 in HEK 293 cells and the proper multiplicity of infection (MOI); ③ hIGF-1 gene expression in MSCs.RESULTS: The adenovirus vector based on adeasy system was constructed successfully and the Ad-hlGF transducing was successfully or efficiently expressed in MSCs cells. The ideal expression of harvested recombinant adenovirus in MSCs was detected by fluorescence microscope, RT-PCR, immunocytochemistry, and Western Blot.CONCLUSION: Adenovirus vector is an effective vector tools for gene expression and wansfection of MSCs. MSCs transduced with Ad-hIGF-1 maybe another option to gene-modified seed cells for articular cartilage tissue engineering.