大鼠Slit2基因慢病毒干扰载体的构建及其对大鼠RPE细胞中Slit2基因的下调作用

摘要

背景 年龄相关性黄斑变性(AMD)是老年人致盲的首要原因.目前,AMD的治疗方式在取得显著疗效的同时亦有一定的不足,寻找新的有效治疗靶点是当前的研究热点. 目的 构建大鼠Slit2基因慢病毒干扰载体,筛选有效干扰序列以用于大鼠视网膜色素上皮(RPE)细胞中Slit2基因沉默,为大鼠相关体内实验奠定基础.方法 设计2条大鼠Slit2基因siRNA序列,退火形成DNA,连接形成慢病毒干扰载体并进行测序鉴定.采用三质粒共转染293T细胞法收获慢病毒(Lv-rSlit2-siRNA),用药物筛选法测定病毒悬液滴度.将大鼠RPE细胞分为空白对照组、空病毒组、Lv-rSlit2-siRNA1组和Lv-rSlit2-siRNA2组,根据分组分别用仅有病毒的载体和不同序列的Lv-rSlit2-siRNA载体转染细胞,分别采用实时荧光定量PCR法和Western blot法测定各组细胞中Slit2 mRNA及蛋白的表达以确定Slit2基因的敲减率,筛选有效干扰序列.采用0、100、200和400μmol/L CoCl2孵育大鼠RPE细胞以制备缺氧细胞模型并转染筛选Lv-rSlit2-siRNA2干扰序列,采用实时荧光定量PCR法和ELISA法测定大鼠RPE细胞中血管内皮生长因子A(VEGFA)表达变化及细胞上清液中VEGFA质量浓度.结果 成功构建2条大鼠Slit2基因慢病毒干扰载体,病毒滴度分别为5×108 TU/ml和3×108 TU/ml,转染病毒后72 h于荧光显微镜下观察RPE细胞慢病毒转染率均在70％以上.Lv-rSlit2-siRNA1组和Lv-rSlit2-siRNA2组大鼠RPE细胞中Slit2 mRNA相对表达量分别为0.67±0.09和0.23±0.11,明显低于空白对照组的1.03±0.31和空病毒组的0.92 ±0.07;Lv-rSlit2-siRNA1组和Lv-rSlit2-siRNA2组大鼠RPE细胞中Slit2蛋白相对表达量分别为0.62±0.07和0.49±0.02,明显低于空白对照组的1.00±0.10和空病毒组的0.95±0.11,差异均有统计学意义(均P＜0.01).0、100、200和400 μmol/L CoCl2作用后,空白对照组和Lv-rSlit2-siRNA2组大鼠RPE细胞中VEGFA mRNA的相对表达量明显不同,差异均有统计学意义(F浓度=127.998,P＜0.01;F分组=69.663,P＜0.01),不同浓度CoCl2作用后各组大鼠RPE细胞中VEGFA蛋白相对表达量均明显不同,差异均有统计学意义(F浓度=17.059,P＜0.01;F分组=91.791,P＜0.01).100、200和400 μmol/LCoCl2作用后Lv-rSlit2-siRNA2组大鼠RPE细胞中VEGFA mRNA表达量及蛋白质量浓度均明显低于空白对照组,差异均有统计学意义(均P＜0.01).结论 大鼠Slit2基因慢病毒干扰载体构建成功并筛选出有效干扰重组序列,其能有效下调大鼠RPE细胞中Slit2基因的表达,并抑制缺氧环境下VEGFA在大鼠RPE细胞中的表达.%Background Age-related macular degeneration (AMD) is the leading cause of blindness in people over 50 years old,of which 90％ cases are caused by choroidal neovascularization (CNV).Current treatments on AMD have gained great achievements,but there are still some drawbacks.So we need to search for new targets to cure CNV.Objective This study was to construct two combined lentiviral vectors for rat Slit2 gene RNA interference (RNAi) and verify its interfering effects on Slit2 gene in rat retinal pigment epithelial (RPE) cells.Methods Two specific siRNA sequences targeting towards rat Slit2 gene were designed and were annealed to DNA sequences.The DNA sequences and GV248-enhanced green flourescent protein (EGFP) vectors were combined together as recombinant vectors and then were identified.The GV248-EGFP vector,helper 1.0 and helper 2.0 were transfected together into 293T cells and the two combined lentiviral vectors for rat Slit2 RNAi were gained from the cell supernatant after 72 hours of transfection.The titers of the combined lentiviral vectors were measured.The cells were divided into blank control group,Lv-EGFP vector group,Lv-rSlit2-siRNA1 group and Lv-rSlit2-siRNA2 group.The interference efficacy of the combined lentiviral vectors targeting to rat Slit2 gene were identified by real-time fluorescence quantitative PCR and Western blot.The sequence with higher interference efficacy was transfected to rat RPE cells again.The transfected and nontransfected rat RPE cells were treated with 0,100,200 and 400 μmol/L CoCl2 for the preparation of hypoxia models.The expression of vascular endothelial growth factor-A (VEGFA) mRNA in rat RPE cells was finally measured by real-time fluorescence quantitative PCR and the concentration of VEGFA protein in cell supernatant was assayed by ELISA.Results The recombined lentiviral vectors for rat Slit2 gene R NAi were successfully constructed.The titers of the two reconbinant sequences were 5× 108 TU/ml and 3×l08 TU/ml,with the transfected rate ≥70％.The relative expression levels of Slit2 mRNA in the Lv-rSlit2-siRNA1 group and LvrSlit2-siRNA2 group were 0.67±0.09 and 0.23±0.11,respectively,which were lower than 1.03±0.31 and 0.92± 0.07 in the blank control group and Lv-EGFP vector group (all at P＜0.01).The expression levels of Slit2 protein in the Lv-rSlit2-siRNA1 group and Lv-rSlit2-siRNA2 group were 0.62±0.07 and 0.49±0.02,respectively,which were lower than 1.00±0.10 in blank control group and 0.95±0.11 in Lv-EGFP vector group (all at P＜0.01).Significant differences were found in the expression of VEGFA mRNA and protein in RPE cells among different concentrations of CoC12 groups (mRNA:F tration =127.998,P＜0.01;Fgroup =69.663,P＜0.01.Protein:F ion =17.059,P＜ 0.01;Fgroup =91.791,P＜0.01),and the expression of VEGFA mRNA and the concentration of VEGFA protein were evidently lower in the Lv-rSlit2-siRNA2 group than those in the blank control group after being treated by 100,200 and 400 μmol/L CoCl2 (all at P＜0.01).Conclusions Recombined lentiviral vector for rat Slit2 gene RNAi is successfully constructed,which can effectively knockdown rat Slit2 gene and inhibit the expression of VEGFA in rat RPE cells.