Transforming growth factor-β receptor antagonism attenuates myocardial fibrosis in mice with cardiac-restricted overexpression of tumor necrosis factor

The mechanisms that are responsible for the development of myocardial fibrosis in inflammatory cardiomyopathy are unknown. We have previously generated lines of transgenic mice with cardiac-restricted overexpression of tumor necrosis factor (MHCsTNF mice), a pro-inflammatory cytokine. The MHCsTNF mice develop a heart failure phenotype that is characterized by progressive myocardial fibrosis, as well as increased levels transforming growth factor-β (TGF-β)(mRNA and protein. In order to determine whether TGF-β-mediated signaling was responsible for the myocardial fibrosis observed in the MHCsTNF mice, we treated MHCsTNF and littermate control mice from 4 to 12 weeks of age with a novel orally available TGF-β receptor antagonist (NP-40208). At the time of terminal study, myocardial collagen content was determined using the picrosirius red technique, and left ventricular (LV) systolic and diastolic function were determined using the Langendorff method. Treatment with NP-40208 resulted in a significant (P < 0.05) 65% decrease in nuclear translocation of Smad 2/3, a significant (P < 0.05), decrease in the heart-weight to body-weight ratio from 6.5 to 5.7, a ∼37% decrease in fibrillar collagen content (P < 0.01) and a significant (P < 0.05) decrease in the LV chamber stiffness by ∼25% in the MHCsTNF mice when compared to diluent-treated controls. Treatment with NP-40208 had no discernable effect on LV systolic function, nor any effect on cardiac myocyte size or fetal gene expression in the MHCsTNF mice. Taken together, these observations suggest that sustained pro-inflammatory signaling in the adult heart is associated with a pro-fibrotic phenotype that arises, at least in part, from TGF-β-mediated signaling, with resultant activation of Smad 2/3, leading to increased myocardial fibrosis and increased LV diastolic chamber stiffness. Returned for 1. revision: 29 August 2007 1. Revision received: 24 September 2007     

基因打靶技术在构建人源体细胞基因敲除或敲入细胞系中的应用

基因打靶技术能够帮助人们认识某些动物个体或细胞表型异常的遗传基础，利用该技术构建的模式生物（例如基因敲除小鼠）已经广泛地应用于人类基因的研究，截至1999年就已经报道了800多个模式小鼠种系。同源重组介导的基因打靶技术（基因敲除或敲入）是判定基因功能的强有力工具。与基因敲除小鼠相比，人类体细胞基因敲除或敲入细胞系构建的报道相对较少，但该项技术在细胞水平上对某些人源基因参与的生化或生理途径的分析是不可替代的。基因打靶技术最常见的应用是通过使所有等位基因连续失活建立基因敲除细胞系；     

受控型蜕皮激素诱导表达截短型hIGF-Ⅰ转基因载体的构建及其在细胞水平上的有效性检测

目的：构建一种可以在哺乳动物细胞中蜕皮激素诱导表达截短型hIGF-Ⅰ的受控型转基因载体，为制备受控型蜕皮激素诱导表达截短型MGF-Ⅰ的转基因小鼠奠定基础。方法：利用分子克隆技术构建受控型蜕皮激素诱导表达截短型hIGF-Ⅰ的转基因载体；将其电转至AM1菌中，利用其中的Cre重组酶将载体上两个同向LoxP序更锚定的新霉素（neomycin）基因删除，解除其对蜕皮激素诱导表达系统的阻断作用，利用PCR、酶切和测序鉴定删除情况；将重组后的载体转染至COS7细胞中进行瞬间表达，蜕皮激素诱导后回收培养上清和细胞裂解物进行Western印迹分析，检测hIGF-Ⅰ的表达情况。结果和结论：成功构建大小为13．6kb的转基因载体pOE-IGF-Ⅰ；转化至AM1中后，PCR、酶切和测序的结果都证明其中的Cre酶能够将载体上neomycin基因删除；重组后的载体转染至COS7细胞中进行诱导表达，Western印迹实验证明截短型MGF-Ⅰ能够在COS7细胞中顺利表达。上述结果证明该蜕皮激素诱导表达截短型hIGF-Ⅰ的受控型转基因载体能够用于转基因小鼠的制备。     

异种移植转基因用含粘附分子-2启动子的人CD59 重组基因的构建

目的：构建含人粘附分子－2（ICAM－2）启动子的人补体调节蛋白CD59重组基因,并钭其用于异种器官移植转基因。方法：利用PCR方法从人血基因组扩增得到ICAM－2启动子、CD59基因的第一内含子片段,经电泳分离、切胶回收纯化得到上述片段,分别双酶、单酶切这两条片段,纯化回收备用;双酶切pcDNA3-CD59真核表达载体,经电泳分离,切胶回收纯化得到不含病毒启动子、含筛选基因Neo的一段pcDNA3-CD59cDNA作为载体序列;ICAM－2启动子片段先与载体进行定向克隆连接反应后转化细菌,阳性转化蓖质粒抽提及酶切鉴定,得到pcDNA3-ICAM2-CD59质粒;再单酶切此质粒,纯化该载体与CD59第一内含子片段连接,转化细菌、抽提质粒,用脂质体将该质粒转染猪血管内皮细菌,流式细胞仪检测CD59蛋白表达。结果：得到pcDNA3-Enhancer-ICAM2-CD59质粒,以EcoR I消化此重组质粒,产生5．5及0．5kb两片段,以Hind Ⅲ消化重组质粒,得到5．45及0．55kb两片段,以Kpn I/Hind Ⅲ双酶切质粒时,出现5．0、0．55、0．4kb 3条片段,对插入子分别进行测序,上述结果完全符合设计要求及正确序列。流式细胞仪检测重组基因表达阳性。结论：含人ICAM－2启动子的CD59重组基因表达载体获得成功,该重组基因构建成功为转基因应用奠定了基础。     

转基因瘤苗的研究

随着分子生物学和基因工程技术的发展,转基因瘤苗取得了重大进展。已获得的转基因瘤苗主要有细胞因子类、肿瘤抗原类、趋化因子类、共刺激分子类、黏附分子类和多个基因共转染瘤苗。转基因瘤苗通过以下三种机制来发挥作用1)增强肿瘤细胞的免疫原性;2)增强机体抗肿瘤免疫反应;3)增强肿瘤细胞免疫原性并降低其致瘤性。经初步评价,转基因瘤苗是安全可靠的,其应用前景广大。     

恶性人脑胶质瘤的HSV-Tk/GCV自杀基因治疗系统的构建及应用研究

目的构建恶性人脑胶质瘤细胞株TJ899的单纯疱疹病毒的胸腺激酶/丙氧鸟苷（HSV-Tk/GCV）自杀基因治疗系统，探讨该体系在脑胶质瘤治疗中的作用。方法采用PCR、RT-PCR、融合PCR、酶切、连接等技术构建由自杀基因pcDNA3.1（-）CMVTK表达载体；用脂质体介导法将pCMVTK质粒转染进入TJ899恶性人脑胶质瘤细胞，并用M IT法检测感染后细胞对（GCV）的敏感性。结果pCMVTK质粒经测序证实含有TK目的基因；脂质体介导Pcmvtk质粒成功转染了TJ899细胞，并在体外实验研究中显示很好的治疗效果。结论建立了作用于恶性人脑胶质瘤细胞株TJ899的HSV-Tk/GCV自杀基因治疗系统，为脑胶质瘤的临床研究打下了基础。     

器官移植免疫耐受的研究进展

综述器官移植免疫耐受研究方面的最新进展，重点阐述诱导和维持免疫耐受的机制和方法。介绍一些具体方案，包括建立异基因骨髓嵌合体，阻断T细胞活化第二信号和转基因技术诱导移植免疫耐受。并对临床免疫耐受的前景和现实问题进行了客观的评价。     

Intracellular signal-responsive artificial gene regulation

In gene therapy, in order to avoid serious side effects due to the unexpected expression of the transgene in non-target cells, transgenes have to be delivered only to the target cells. In response to this issue, many researchers have aimed at developing target cell-selective gene carriers using active targeting strategies. However, such methodology does not always work, because an ideal molecular marker, which is specific to the target disease cells, is not always available. In this study, we introduce a new concept regarding target disease cell-selective gene therapy (D-RECS). Here, we use intracellular signals, which are activated to an extraordinary degree only in the target disease cells, as a trigger for transgene expression using polymer–peptide conjugates. This strategy could actually activate gene expression in the target signal-activated cells only. Hyper-activation of certain intracellular signals has been reported in many diseases. Thus, this new strategy is expected to provide a powerful methodology for future gene therapy. In this review, the basic concept, some examples, and the molecular design of D-RECS carriers are introduced.     

Reciprocal homologous recombination in or near antibody VDJ genes

To determine if rearranged heavy chain variable (VDJ) genes can recombine with each other by crossing over of DNA strands, we constructed a transgene that contained a promoter, VDJ gene, reporter gene to detect crossover events, intron enhancer, matrix attachment region, and constant gene for IgM (Cμ). Following immunization of transgenic mice, hybrid molecules were isolated from B cell DNA which contained the transgene recombined with the endogenous IgH locus. Reciprocal products of crossovers were detected by plasmid rescue and PCR amplification, and they were sequenced. Recombination occurred somewhere within 147 bp of homology that contained the J_H4 gene segment and 3′ flanking DNA. The recombined transgenes had a 20-fold increase in mutation in the VDJ region compared to nonrecombined transgenes, which indicates that DNA sequences 3′ of the Cμ gene in the endogenous IgH locus are necessary for full activity of the mutator mechanism. The recovery of recombinants between VDJ transgenes and endogenous VDJ genes raises the possibility that reciprocal recombination may somatically diversify rearranged genes between maternal and paternal alleles.