造影剂、超声波介导的基因治疗技术

目前基因治疗受阻于缺乏安全有效的载体。病毒类载体和非病毒类载体最大的不足之处在于不安全和转染效率低。超声波作为一种物理转染方法会造成组织损伤。近年来,超声造影剂的出现使研究者对超声波介导的基因转染技术有了新的认识。微气泡作为一种超声造影剂能携带基因物质,在超声波的作用下,“载体”微泡破裂,并在经超声辐照的区域高浓度释放其所携带的基因物质。同时,微气泡破裂会导致局部组织细胞膜通透性增高,从而使外源性基因更易被摄取。     

超声可控释药体系研究进展

超声可控释药体系是一种新兴的靶向给药及基因转运方法。以超声敏感材料作为药物或基因转送的载体,当超声辐照于靶组织或靶器官时, 靶体内载体可定向释放出包裹或附着的基因或药物, 实现对负载药物的定时定量定点释放和提高药物输送效率或基因转染率的目的。文中对超声可控释药体系的作用机制、超声敏感载体材料及生物医学应用等方面进行综述,最后对该领域目前存在的问题和今后的发展方向提出了一些看法。     

受体介导的基因转移研究进展

受体介导的基因转移具有靶向、高效、安全、低免疫原性和制备简单等许多优点。简要综述了受体介导基因转移的主要类型、影响受体介导基因转移的因素和提高基因转移效率的策略等方面的进展。     

逆转录病毒介导DNA修复蛋白在人骨髓细胞中的表达和抗性研究

目的增强造血细胞对化疗药物的耐药表型,探讨逆转录病毒介导的基因转移效率及耐药基因的特性和在造血细胞保护性基因治疗中的作用和意义.方法应用RT-PCR从人肝组织中获得编码六氧甲基鸟嘌呤-DNA-甲基转移酶(MGMT)cDNA,将其克隆于pGEM-T质粒载体并构建了逆转录病毒载体G1Na-MGMT,应用脂质体LipofectAMINE基因转移法将后者导入GP+E86和PA317病毒包装细胞,以BCNU加压筛选后的阳性克隆上清经乒乓效应后继而感染K562细胞和人造血细胞.应用PCR,Southernblot,RT-PCR,Westernblot及MTT法检测人MGMT基因在细胞中的转移和表达.结果酶切鉴定及DNA测序证实其MGMTcDNA克隆的正确性,脂质体介导方法成功将其导入病毒包装细胞,BCNU加压筛选和乒乓感染法使病毒效价达8.6×106CFU/ml,逆转录病毒载体介导的MGMT基因在K562细胞及人造血细胞中获得有效转移和表达.结论MGMT耐药基因的成功克隆并导入骨髓造血细胞且获高效表达对开展肿瘤基因治疗的临床研究奠定了实验基础.     

超声微泡介导pEGFP-N1转染大鼠牙囊细胞:细胞生物学性质相对稳定

背景:利用超声波和微泡对比剂相互作用,产生空化效应和机械效应,破坏细胞膜的完整性,产生暂时性、可逆性的小孔,增加细胞膜的通透性,增强微泡载体对基因的转移,提高基因转染率。目的:探讨在超声波辐照下微泡对比剂介导p EGFP-N1质粒转染SD大鼠乳鼠牙囊细胞的效率及安全性。方法:体外原代培养新生SD大鼠牙囊细胞并传至第4代,在不同条件下采用p EGFP-N1质粒转染乳鼠牙囊细胞。以不同的超声辐照时间(15,30,45,60 s)和辐照强度(0.5,1 W/cm2)两两组合进行辐照,筛选较高转染效率的参数组合并应用于后续实验。实验分组为质粒组、微泡+质粒组、超声+质粒组、超声+微泡+质粒组和脂质体+质粒组。转染48 h后倒置荧光显微镜观察p EGFP表达,MTT法检测转染后的乳鼠牙囊细胞增殖抑制率。结果与结论:超声强度为0.5 W/cm2且辐照时间为30 s时转染率明显高于其他超声参数组合。该条件下超声微泡介导p EGFP-N1质粒对乳鼠牙囊细胞的转染率高于传统脂质体介导的转染率,且对细胞活力无明显影响。提示超声微泡能安全、高效介导p EGFP-N1质粒转染大鼠牙囊细胞,其细胞生物学性质相对稳定,可为牙周组织工程提供一种较理想的基因转染方法。     

阴沟肠杆菌喹诺酮类耐药qnr基因的发现

细菌对喹诺酮类药物的耐药机制主要是药物作用靶位的变异、细菌细胞膜通透性改变和／或主动外排系统过度表达导致药物在细菌体内浓度降低，这两种耐药机制由染色体介导引起，不具有水平传播性。最近Martine-Martinez L等发现了一个可编码喹诺酮耐药的多重耐药基因咿，qnr,qnr基因是由可接合质粒介导的喹诺酮类耐药基因，作用机制是其编码的蛋白质对喹诺酮类药物靶位点的保护，从而导致药物治疗失败。本文对2003年9月—2005年6月解放军98医院分离的44株阴沟肠杆菌中qnr基因进行筛查。     

腺病毒介导血管内皮细胞生长因子基因体外转染人脐带间充质干细胞

目的探讨腺病毒介导血管内皮细胞生长因子(VEGF)基因转染人脐带间充质干细胞(UCMSCs)后目的基因表达情况及对UCMSCs生长增生的影响。方法 UCMSCs传代培养后,以腺病毒介导绿色荧光蛋白(GFP)基因进行体外转染,倒置荧光显微镜下观察细胞转染效果,流式细胞仪检测细胞转染效率,确定最佳的病毒感染复数(MOI)。将实验分为VEGF基因转染组和未转染组。转染组在最佳MOI值条件下以腺病毒介导VEGF基因体外转染UCMSCs;未转染组以PBS代替病毒液。通过免疫荧光染色及Western blotting检测两组UCMSCs VEGF蛋白的表达情况,RT-PCR检测VEGF基因mRNA的表达情况,ELISA检测培养液中VEGF浓度,MTT法评价转染后对UCMSCs生长增生的影响。结果腺病毒介导的GFP基因对于UCMSCs具有较高的转染效率,转染效率与MOI值具有量效关系,当MOI为100倍时,转染效率达95%。转染VEGF基因后2d,UCMSCs在mRNA和蛋白水平上均可有效表达VEGF,免疫荧光染色、RT-PCR、Western blotting显示转染组明显表达VEGF,ELISA检测结果显示7d时达到表达高峰,13d后仍可检测到VEGF的表达。介导VEGF基因转染的腺病毒对UCMSCs的生长增生没有明显影响。结论 UCMSCs是一种较理想的基因载体细胞,腺病毒介导VEGF基因可以有效转染UCMSCs,转染后VEGF基因可获得较高的表达水平。     

腺病毒载体介导gfp基因在树突细胞的转导及其影响因素的分析

目的：研究腺病毒载体介导外源基因在人树突细胞转染的有效方法。方法：绿色荧光蛋白（gfp）报告基因重组腺病毒的构建采用直接连接法。人树突细胞的制备通过分离人外周血单核细胞，然后在体外经过诱导过程再生。结果：经腺病毒介导实现了gfp基因在树突细胞的转导和表达。病毒滴度对转导效率影响较大，只有使用高滴度（MOI〉100）的重组腺病毒才能获得较高的转导效率（40％以上）；脂质体和多聚赖氨酸可以明显提高转导效率（提高50％左右）。转导效率最高可达65％左右。结论：由腺病毒介导进行树突细胞的转基因需要较高的病毒滴度；脂质体和多聚赖氨酸可以提高基因的转导效率。     

DNA修复蛋白MGMT基因的克隆及转导脐血CD34+细胞后耐药特征的研究

目的 增强脐血CD34+造血细胞对化疗药物的耐药表型,探讨逆转录病毒介导的基因转移效率和耐药基因特性,以及在脐血造血干细胞保护性基因治疗中的作用和意义.方法 应用逆转录-聚合酶链反应(RT-PCR)从人肝组织中获得编码六氧甲基鸟嘌呤-DNA-甲基转移酶(O6-methylguanine-DNA-methyltransferase,MGMT)cDNA;利用基因重组技术,将其克隆于pGEM-T质粒载体并构建了逆转录病毒载体G1Na-MGMT;应用脂质体LipofectAMINE基因转移法将后者导入GP+E86和PA317病毒包装细胞,以卡氮芥1,3-Bis(2-Chloroethyl)-1-Nitrosourea(BCNU)加压筛选后的阳性克隆上清经乒乓效应后继而感染脐血CD34+细胞.应用PCR,Southern Blot,RT-PCR,Northern blot,Western Blot及MTT法检测MGMT基因在脐血CD34+细胞中的转移和表达.结果 酶切鉴定及DNA测序证实了MGMT cDNA克隆的正确性,脂质体介导方法成功将其导入病毒包装细胞,BCNU加压筛选和乒乓感染法使病毒效价达1.6×106CFU/ml,逆转录病毒载体介导的MGMT基因在脐血造血干细胞中获得了有效转移和表达.转MGMT耐药基因脐血造血干/祖细胞对BCNU的抗药性较对照组提高了4倍.结论 DNA修复蛋白MGMT基因的克隆并导入脐血造血干/祖细胞可以明显提高靶细胞的耐药性.     

Physical Non-Viral Gene Delivery Methods for Tissue Engineering

The integration of gene therapy into tissue engineering to control differentiation and direct tissue formation is not a new concept; however, successful delivery of nucleic acids into primary cells, progenitor cells, and stem cells has proven exceptionally challenging. Viral vectors are generally highly effective at delivering nucleic acids to a variety of cell populations, both dividing and non-dividing, yet these viral vectors are marred by significant safety concerns. Non-viral vectors are preferred for gene therapy, despite lower transfection efficiencies, and possess many customizable attributes that are desirable for tissue engineering applications. However, there is no single non-viral gene delivery strategy that “fits-all” cell types and tissues. Thus, there is a compelling opportunity to examine different non-viral vectors, especially physical vectors, and compare their relative degrees of success. This review examines the advantages and disadvantages of physical non-viral methods (i.e., microinjection, ballistic gene delivery, electroporation, sonoporation, laser irradiation, magnetofection, and electric field-induced molecular vibration), with particular attention given to electroporation because of its versatility, with further special emphasis on Nucleofection?. In addition, attributes of cellular character that can be used to improve differentiation strategies are examined for tissue engineering applications. Ultimately, electroporation exhibits a high transfection efficiency in many cell types, which is highly desirable for tissue engineering applications, but electroporation and other physical non-viral gene delivery methods are still limited by poor cell viability. Overcoming the challenge of poor cell viability in highly efficient physical non-viral techniques is the key to using gene delivery to enhance tissue engineering applications.     

Gene delivery in bone tissue engineering: progress and prospects using viral and nonviral strategies

Bone tissue loss as a consequence of the natural aging process or as a result of trauma and degenerative disease has led to the need for procedures to generate cartilage and bone for a variety of orthopedic applications. The ability to transfer genes into multipotential mesenchymal stem cells, while still in its infancy, offers considerable therapeutic hope in a variety of musculoskeletal disorders. However, the choice of gene delivery method is key. This review examines the various techniques and methods currently available to enable gene transfer into a target population from viral methods (transduction) to nonviral (transfection) methods and the limitations associated with each method. The potential applications and current understanding of each method are presented. Given the demographic challenge of an aging population, the ultimate goal remains the development of simple, safe, and reproducible strategies for gene delivery that will address the pressing orthopedic clinical imperatives of many.     

Electrotransfer as a non viral method of gene delivery

Over the last few decades, various vectors have been developed in the field of gene therapy. There still exist a number of important unresolved problems associated with the use of viral as well as non viral vectors. These techniques can suffer from secondary toxicity or low gene transfer efficiency. Therefore an efficient and safe method of DNA delivery still needs to be found for medical applications. DNA electrotransfer is a physical method that consists of the local application of electric pulses after the introduction of DNA into the extra cellular medium. As electrotransfer has proven to be one of the most efficient and simple non viral methods of delivery, it may provide an important alternative technique in the field of gene therapy. The present review focuses on questions related to the mechanism of DNA electrotransfer, i.e. the basic physical processes responsible for the electropermeabilisation of lipid membranes. It also addresses the current limitations of the method as applied to DNA transfer, in particular its efficiency in achieving in vitro gene expression in cells and also its potential use for in vivo gene delivery.     

Sustained in vivo gene delivery from agarose hydrogel prolongs nonviral gene expression in skin

Prolonging gene expression in skin using safe, nonviral gene delivery techniques could impact skin regeneration and wound healing, decrease infection, and potentially improve the success of tissue-engineered skin. To this end, an injectable, agarose-based delivery system was tested and shown to prolong nonviral gene expression in the skin. DNA was compacted with polylysine to improve DNA stability in the presence of nucleases. Up to 25 microg of compacted luciferase plasmid with or without agarose hydrogel was injected intradermally in rodents. Bioluminescence imaging was used for longitudinal, noninvasive monitoring of gene expression in vivo for 35 days. Injections of DNA in solution produced gene expression for only 5-7 days, whereas the sustained release of compacted DNA from the agarose system prolonged expression, with more than 500 pg (20% of day 1 levels) of luciferase per site for at least 35 days. Southern blotting confirmed that the agarose system extended DNA retention, with significant plasmid present through day 7, as compared with DNA in solution, which had detectable DNA only on day 1. Histology revealed that agarose invoked a wound-healing response through day 14. Tissue-engineering and wound-healing applications may benefit from the agarose gene delivery system.     

Baculoviral vectors for gene delivery: a review

Baculovirus has emerged as a novel vector for in vivo and in vitro gene delivery. In addition, the applications of baculovirus-mediated gene transfer have been explosively expanded to drug screening, eucaryotic gene display, cancer therapy and tissue engineering, etc. The capability of baculovirus viral envelope for protein/peptide display also renders itself a potential vaccine delivery platform. This paper reviews the history, factors influencing baculovirus-mediated gene delivery and emerging in vitro, in vivo and ex vivo applications. Efforts aimed at overcoming current existing bottlenecks and recent progresses in addressing the safety concerns are particularly emphasized.     

Substrate-mediated delivery from self-assembled monolayers: effect of surface ionization, hydrophilicity, and patterning

Gene transfer has many potential applications in basic and applied sciences. In vitro, DNA delivery can be enhanced by increasing the concentration of DNA in the cellular microenvironment through immobilization of DNA to a substrate that supports cell adhesion. Substrate-mediated delivery describes the immobilization of DNA, complexed with cationic lipids or polymers, to a biomaterial or substrate. As surface properties are critical to the efficiency of the surface delivery approach, self-assembled monolayers (SAMs) of alkanethiols on gold were used to correlate surface chemistry of the substrate to binding, release, and transfection of non-specifically immobilized complexes. Surface hydrophobicity and ionization were found to mediate both DNA complex immobilization and transfection, but had no effect on complex release. Additionally, SAMs were used in conjunction with soft lithographic techniques to imprint substrates with specific patterns, resulting in patterned DNA complex deposition and transfection, with transfection efficiencies in the patterns nearing 40%. Controlling the interactions between complexes and substrates, with the potential for patterned delivery, can be used to locally enhance or regulate gene transfer, with applications to tissue engineering scaffolds and transfected cell arrays.     

Muscular gene transfer using nonviral vectors

Skeletal muscle is a target tissue of choice for the gene therapy of both muscle and non-muscle disorders. Investigations of gene transfer into muscle have progressed considerably from the expression of plasmid reporter genes to the production of therapeutic proteins such as trophic factors, hormones, antigens, ion channels or cytoskeletal proteins. Viral vectors are intrinsically the most efficient vehicles to deliver genes into skeletal muscles. But, because viruses are associated with a variety of problems (such as immune and inflammatory responses, toxicity, limited large scale production yields, limitations in the size of the carried therapeutic genes), nonviral vectors remain a viable alternative. In addition, as nonviral vectors allow to transfer genetic structures of various sizes (including large plasmid DNA carrying full-length coding sequences of the gene of interest), they can be used in various gene therapy approaches. However, given the lack of efficiency of nonviral vectors in experimental studies and in the clinical settings, the overall outcome clearly indicates that improved synthetic vectors and/or delivery techniques are required for successful clinical gene therapy. Today, most of the potential muscle-targeted clinical applications seem geared toward peripheral ischemia (mainly through local injections) and cancer and infectious vaccines, and one locoregional administration of naked DNA in Duchenne muscular dystrophy. This review updates the developments in clinical applications of the various plasmid-based non-viral methods under investigation for the delivery of genes to muscles.     

Fabrication of polymeric microparticles for drug delivery by soft lithography

Soft lithographic techniques were used to fabricate polymeric microparticles for drug delivery applications. The microparticles were made of thermoplastics and thermosets from different types of precursors including reactive resin and polymer solutions in organic solvents or water. The microparticles produced using these methods were made of widely used polymers for drug delivery with highly uniform sizes, plate-like morphology, and well-defined lateral sizes and shapes, making them potentially useful for drug delivery applications and as platform for the construction of multi-functional drug delivery devices.     

Polysaccharide gene transfection agents

Gene delivery is a promising technique that involves in vitro or in vivo introduction of exogenous genes into cells for experimental and therapeutic purposes. Successful gene delivery depends on the development of effective and safe delivery vectors. Two main delivery systems, viral and non-viral gene carriers, are currently deployed for gene therapy. While most current gene therapy clinical trials are based on viral approaches, non-viral gene medicines have also emerged as potentially safe and effective for the treatment of a wide variety of genetic and acquired diseases. Non-viral technologies consist of plasmid-based expression systems containing a gene associated with the synthetic gene delivery vector. Polysaccharides compile a large family of heterogenic sequences of monomers with various applications and several advantages as gene delivery agents. This chapter, compiles the recent progress in polysaccharide based gene delivery, it also provides an overview and recent developments of polysaccharide employed for in vitro and in vivo delivery of therapeutically important nucleotides, e.g. plasmid DNA and small interfering RNA.