重组腺相关病毒载体2型转染骨髓间充质干细胞的体外实验

背景目前应用于基因治疗的病毒载体中,重组腺相关病毒载体2型载体与腺病毒和反转录病毒载体比较,由于其无致病性,引起学者们的关注.目的观察体外重组腺相关病毒载体2型转染骨髓间充质干细胞,并用其作为携带基因表达的载体进行急性髓性白血病基因治疗的可能性.设计开放性实验.单位南方医科大学南方医院的血液科.材料实验于2004-02/07在南方医科大学南方医院的血液科实验室完成.本实验所用的骨髓间充质干细胞来自急性髓性白血病6例初发患者和4名健康成年志愿者的第3～5代传代细胞.方法从初发的急性髓性白血病患者和正常健康志愿者髂后上棘做骨髓穿刺抽取6～10 mL肝素抗凝的骨髓,分离培养出间充质干细胞,用包含增强型绿色荧光蛋白的重组腺相关病毒载体2型感染间充质干细胞,将获取的骨髓间充质干细胞加入含一定感染复数(感染复数=1×102,1×103,1×104,1×105,1×106,1×107)的增强型绿色荧光蛋白的重组腺相关病毒载体2型病毒载体的不完全培养液,10～14 d后在相差荧光显微镜下或用流式细胞仪观测绿色荧光蛋白的表达.在体外培养条件下观察绿色荧光蛋白在经过重组腺相关病毒载体2型转导的骨髓间充质干细胞中的表达.体外观察经增强型绿色荧光蛋白的重组腺相关病毒载体2型转导并被新霉素筛选后绿色荧光蛋白在被转导的骨髓间充质干细胞中的表达.通过相差荧光显微镜下确证绿色荧光蛋白表达后,在BD流式细胞仪上检测绿色荧光蛋白的表达.主要观察指标①增强型绿色荧光蛋白的重组腺相关病毒载体2型对骨髓间充质干细胞的转染率分析.②在转染后的不同时间点用相差荧光显微镜和流式细胞仪观察绿色荧光蛋白的表达情况.结果①转染率分析增强型绿色荧光蛋白的重组腺相关病毒载体2型对来源于健康志愿者和急性髓性白血病患者的骨髓间充质干细胞的转染率均不高,转染率在0.3%～1.4%.转染后10～14 d绿色荧光蛋白开始表达,一般感染条件绿色荧光蛋白阳性骨髓间充质干细胞所占比例为(1.030±0.034)%,重复3轮感染条件下为(1.140±0.036)%,脂质体协助感染条件下为(1.380±0.054)%,改变转染条件(包括重复感染,延长感染时间,增加感染复数,脂质体协助转染)亦不能明显增加转染率(P＞0.05),而增强型绿色荧光蛋白的重组腺相关病毒载体2型却能高效的转染其包装细胞293细胞.②绿色荧光蛋白在体外长期稳定表达分析实验观察61 d内,绿色荧光蛋白保持低水平长期稳定表达,在转染后的12～33 d,绿色荧光蛋白阳性的骨髓间充质干细胞从起始时的1.16%下降到0.5%～0.6%,33～61 d一直维持在这一水平;经过新霉素筛选30 d后,表达绿色荧光蛋白的骨髓间充质干细胞达到6.6%左右,在体外继续传代培养,在体外观察的100 d中,表达绿色荧光蛋白的骨髓间充质干细胞一直维持在6%的水平.结论重组腺相关病毒载体2型介导的基因转导的优势是安全、无免疫反应,目的基因能够长期稳定表达.重组腺相关病毒载体和骨髓间充质干细胞可用于体外基因治疗,其将来可能成为全身基因治疗的良好载体.

Bone marrow mesenchymal stem cell gene modified by recombinant adeno-associated virus-2 in vitro

BACKGROUND: Recombinant adeno-associated virus 2(rAAV-2) has attracted considerable attention due to its nonpathogenic nature in contrast to other viral vectors such as adenoviral and retroviral vectors in gene therapy attempts.OBJECTIVE: To explore rAAV-2 transduction to bone marrow mesenchymalstem cell(BMSC) in vitro and evaluate the possibility of using rAAV-2 as a vector for gene therapy of acute myelogenous leukemia(AML).DESIGN: An open experiment with cells as the observational subjects.SETTING: Department of Hematology, Nanfang Hospital, Southern Medical University.MATERIALS: The experiment was conducted in the Department of Hematology, Nanfang Hospital, Southern Medical University from February to July 2004. We used passages 3 to 5 BMSCs derived from six de novo AML patients and four healthy volunteers in this study.METHODS: BMSC was isolated from 6 to 10 mL of bone marrow aspirates obtained from the iliac crests of the patients who had been diagnosed as having de novo AML and from those of healthy volunteers. The acquired BMSC was infected by rAAV-2 which contained enhanced green fluorescent protein (rAAV-2-eGFP) at different multiplicity of infection(MOI) (MOI = 1 × 102,1 × 103, 1 × 104, 1 × 105, 1 × 106, 1 × 107) . Then we observed through phase contrast fluorescent microscope and flow cytometer to evaluate green fluorescent protein(GFP) expression 10 to 14 days after transduction. GFP expression was observed as the rAAV-2-eGFP transduced BMSC cultured in vitro. We also observed the in vitro gene expression profile of GFP in rAAV-2-eGFP transduced BMSC which was selected by neomycin ( G418). First, we confirmed GFP expression in BMSC through phase contrast fluorescent microscope, then on flow cytometer to detect the percentage of GFP expression.MAIN OUTCOME MEASURES: The efficiency of rAAV-2-eGFP transduction to BMSC. GFP expression was observed through phase contrast fluorescent microscope and flow cytometer at different time points after transduction.rAAV-2-eGFP to BMSC derived from normal volunteers and AML patients had no significant differences. GFP began to express 10 to 14 days after transduction, and the transduction efficiency ranged from 0. 3% to 1.4%. By changing infection condition, we could not make a higher transduction efficiency( P ＞ 0.05) . One round infection of BMSC by rAAV-2-eGFP at a MOI of 1 × 105 was ( 1. 030 ± 0. 034) %, 3 rounds of infection of BMSC by rAAV-2-eGFP at a MOI of 1 × 105 was (1. 140 ±0. 036)%, and coinfected by LipofectAMINE was (1. 380 ± 0. 054)%. However, 293 cell line which was the package cell of rAAV-2 could be efficiently transduced by AML patients transduced by rAAV-2-eGFP at MOI = 1 × 105: The percentage of GFP expression cell gradually decreased from 1.14% at day 12 after transduction to 0. 6% as cell passaged from 2 to 3, and maintained at a level of 0. 5% to 0. 6% later on till 61 days after transduction. After selected by neomycin(G418) 1 month later, rAAV-2-eGFP transduced BMSCs could maintain a long-term GFP expression at a level of 6.0% in vitro without significant decay within 100 days of observation period after transduction.CONCLUSION: The advantages of rAAV-2 mediated gene transduction lie in safety, no immune response to the host, and long-term expression maintained by the target gene. rAAV-2 and BMSC can be used for in vitro gene therapy, and as a systemic gene delivery system, it might be an alternative for systemic gene therapy in the future.