大鼠CXCR4基因RNAi慢病毒载体的构建及其在骨髓间质干细胞中的表达

为深入研究CXCR4在骨髓间质干细胞(MSCs)体内迁移中的作用, 构建CXCR4基因RNA干扰(RNAi)慢病毒载体并实现其在大鼠MSCs (rMSCs)中表达。根据大鼠CXCR4 mRNA序列, 设计并合成包含各靶序列的互补DNA链,插入pSUPER载体的H1 RNA启动子后面, 产生pRiCXCR4, 将其中的CXCR4 shRNA表达结构酶切插入慢病毒载体质粒pNL-EGFP, 产生pNL-RiCXCR4-EGFP。在脂质体介导下与包装质粒pHELPER和包膜质粒pVSVG共转染293T细胞, 包装生产慢病毒,测定慢病毒功能滴度。慢病毒转导rMSCs后, 用Real-time RT-PCR、Western blotting和流式细胞术检测RNAi组(CXCR4a、CXCR4b和CXCR4c)、空载体组(Mock)和对照组(Control)中CXCR4表达情况。结果显示, 酶切和测序证实pRiCXCR4质粒构建正确, 产生能同时表达增强型绿色荧光蛋白(EGFP)和CXCR4 shRNA的慢病毒载体质粒pNL-RiCXCR4-EGFP, 未浓缩和浓缩慢病毒悬液的功能滴度分别为6.4×104TU/mL和6.9×106TU/mL。慢病毒转导rMSCs 48 h后, 与空载体组和空白组相比, 3个RNAi组均不同程度抑制CXCR4表达, CXCR4b-MSC组在mRNA水平抑制了95.6%, 抑制作用最明显。大鼠CXCR4基因RNAi慢病毒载体构建成功, 为深入研究CXCR4在rMSCs向损伤组织定向迁移的作用奠定了基础。

Construction of rat CXCR4 gene lentiviral RNA interference vector and its expression in mesenchymal stem cells

To construct the lentiviral RNA interference (RNAi) vector of rat CXCR4 gene, three target sequences were selected according to rat CXCR4 mRNA sequence, the complementary DNA contained both sense and antisense oligonucleotides were designed and synthesized. After phosphorylation and annealing, these double-strand DNA were cloned to Bgl II and Hind III sites of pSUPER. Then the product pRiCXCR4 was confirmed by electrophoresis and sequencing. Next, CXCR4 shRNA was cloned to a transfer vector of lentivirus, pNL-EGFP, and pNL-RiCXCR4-EGFP was produced. It was confirmed by digestion and sequencing that CXCR4 shRNA expression structure was correctly cloned to pSUPER and pNL-EGFP respectively. Three plasmids, pNL-RiCXCR4-EGFP, pHELPER and pVSVG were cotransfected into 293T to package lentivirus particles. The functional titer of obtained virus was determined by flow cytometry after transduction in 293T, the resulting functional titer of unconcentrated virus and concentrated virus were 6.4×104 TU/mL and 6.9×106 TU/mL respectively. After the rat mesenchymal stem cells (rMSCs) were transduced with the constructed lentiviral vectors, real-time RT-PCR, Western blotting and flow cytometry were used to evaluate the level of CXCR4 expression. Compared with control group, the CXCR4 mRNA expression were obviously suppressed in all three experimental groups (rMSCs-CXCR4a, rMSCs-CXCR4b, rMSCs-CXCR4c), especially the expression rate in rMSCs-CXCR4b group was reduced by 95.6%. The RNAi lentivirus vector of rat CXCR4 gene has been constructed successfully. This greatly facilitates the further studies such as evaluation the role of CXCR4 in rMSCs recruitment to damaged tissue.