绿色荧光蛋白腺病毒表达载体在大鼠肌源性干细胞标记中的应用

目的:对大鼠肌源性干细胞转染携带绿色荧光蛋白基因的腺病毒表达载体,为进一步行标记细胞移植治疗实验奠定基础。方法:复苏并培养人胚胎肾293细胞,进行包装重组及大规模扩增腺病毒;原代培养大鼠肌源性干细胞并进行GFP基因转染,荧光显微镜观察转染情况并计算转染率。结果:人胚胎肾293细胞在普通培养条件下生长良好,加入Ad-GFP病毒液后48h荧光显微镜观察绝大多数细胞呈悬浮状态,带有较强的绿色荧光;转染肌源性干细胞后呈Desmin免疫组织化学显色阳性;48h荧光转染率为83.14%,4d为78.35%,8d为75.12%。结论:采用携带绿色荧光蛋白基因的腺病毒表达载体标记肌源性干细胞的方法安全可靠、简便有效,且能保持肌源性干细胞原有生物学特性。     

Nestin-specific green fluorescent protein expression in embryonic stem cell-derived neural precursor cells used for transplantation

Expression of the enhanced green fluorescent protein (EGFP) under control of a thymidine kinase promoter/nestin second intron was specifically detected in nestin immunoreactive neural precursor cells after selection of murine embryonic stem (ES) cells in chemically defined medium. Allowing differentiation in vitro, the capacity of these cells to give rise to astroglia, oligodendroglia, and neurones was investigated. After intracerebral transplantation, long-lasting integration of precursor cells into the host tissue was observed, serving as a pool for successive neuronal and glial differentiation. EGFP expression by ES cell-derived neural precursor cells may be a valuable tool to optimize protocols for maintenance and expansion of these cells in vitro as well as in vivo after intracerebral transplantation. In addition, preparative fluorescence-activated cell sorting of EGFP-labeled neural precursor cells should be useful for standardization of a donor cell population for cell replacement therapies.     

慢病毒介导增强型绿色荧光蛋白基因修饰人骨髓基质细胞

背景：原代细胞的转染效率低下一直是制约其发展的主要因素之一,慢病毒转染以其独特的优势成为各种干细胞基因修饰良好的转染方法。 目的：验证慢病毒载体介导增强型绿色荧光蛋白基因修饰人骨髓基质细胞的可行性。 方法：将携带增强型绿色荧光蛋白基因的慢病毒在含血清或无血清条件下按不同的MOI值分别转染人骨髓基质细胞,长期观察荧光蛋白表达情况。将经修饰的细胞通过立体定向移植入大鼠纹状体内,观察移植细胞的存活及目的基因的表达情况。 结果与结论：基因转染48 h后,可见人骨髓基质细胞成功表达绿色荧光蛋白,无血清条件下的转染效率高于含血清条件下的转染效率,转染成功的细胞在体外持续培养2个月以上未见明显的荧光消减。转染后的细胞可在大鼠纹状体存活并持续表达绿色荧光蛋白2个月以上。提示慢病毒是一种高效的转染人骨髓基质细胞的载体,慢病毒载体介导增强型绿色荧光蛋白基因转染可以作为人骨髓基质细胞的示踪标志用于体内移植研究。     

Isolation of mesenchymal stem cells (MSCs) from green fluorescent protein positive (GFP+) transgenic rodents: the grass is not always green(er)

Cellular therapy is under intense basic science and clinical investigation as a therapeutic intervention. One of the challenges lies in tracking these cells in vivo. While there are many ways to label and track cells--each with strengths and weaknesses--the green fluorescent protein (GFP) is a reporter gene commonly employed. We report a significant and consistent reduction in the expression of GFP with the culture of mesenchymal stem cells (MSCs) isolated from the bone marrow of GFP(+) transgenic rodents. After MSC isolation and immunophenotype characterization, along with co-localization with GFP, MSCs were evaluated for GFP expression through flow cytometry and fluorescent microscopy, revealing that only 50% of the cells expressed GFP. Differentiation of the cells to adipocytes did not alter the GFP expression significantly. Incubation with an anti-GFP antibody increased the fluorescent intensity of the GFP-expressing and some of the GFP nonexpressing cells. Incubation of MSCs with a histone deacetylase inhibitor, trichostatin A, did not significantly alter GFP expression, while incubation with a DNA demethylation reagent, 5-azacytidine, increased GFP expression, suggesting that epigenetic modification by DNA methylation may play a role in GFP expression among MSCs.     

Notch1 but not Notch2 is essential for generating hematopoietic stem cells from endothelial cells

Hematopoietic stem cells (HSCs) are thought to arise in the aorta-gonad-mesonephros (AGM) region of embryo proper, although HSC activity can be detected in yolk sac (YS) and paraaortic splanchnopleura (P-Sp) when transplanted in newborn mice. We examined the role of Notch signaling in embryonic hematopoiesis. The activity of colony-forming cells in the YS from Notch1(-/-) embryos was comparable to that of wild-type embryos. However, in vitro and in vivo definitive hematopoietic activities from YS and P-Sp were severely impaired in Notch1(-/-) embryos. The population representing hemogenic endothelial cells, however, did not decrease. In contrast, Notch2(-/-) embryos showed no hematopoietic deficiency. These data indicate that Notch1, but not Notch2, is essential for generating hematopoietic stem cells from endothelial cells.     

应用RNAi抑制细胞中绿色荧光蛋白的表达

目的 在293T和Mel细胞中研究RNA干扰（RNA interference，RNAi）对绿色荧光蛋白（enhanced green fluorescent protein，eGFP）表达的沉默作用。方法 以巢式PCR方法从人胚肾293T细胞中克隆出依赖于RNA聚合酶Ⅲ的H1启动子，并用于驱动RNAi片段的合成；构建能抑制eGFP特异性表达的RNAi载体（TRl）。将eGFP载体和RNAi干扰载体共转染293T和Mel两类细胞中，应用荧光显微镜观察、逆转录-PCR、荧光辅助细胞分选技术和定量逆转录-PCR方法分析上述细胞中RNAi对eGFP表达的抑制情况。结果 RNAi载体能有效地使293T和Mel细胞中红系特异的eGFP表达量均降低约50％以上。结论 本文构建的RNAi载体能有效的抑制目的基因eGFP在细胞中的表达。     

Expression of the gene for hematopoietic cell specific protein is not restricted to cells of hematopoietic origin

Hematopoietic cell line specific protein (HS1) is an intracellular signaling protein that has been reported as specifically expressed in hematopoietic cells. HS1 is known as a major substrate of protein-tyrosine kinases following activation by B-cell or T-cell receptor complexes. We report the first evidence that HS1 is also expressed in a variety of tissues different from hematopoietic tissues by using sensitive expression analysis including real-time quantitative RT-PCR. While former studies on HS1-expression were mostly limited to cells of hematopoietic origin, we screened a larger number of human tissues including tumor samples. Normal lung tissue showed a high degree of HS1 expression, second to the expression of hematopoietic cells. Expression of HS1 in tumor tissues was also clearly detectable. Our findings suggest that the signaling protein HS1 is involved in pathways different from the ones that have a specific role in the intracellular processes of hematopoietic cells.     

Sofast介导增强性绿色荧光蛋白基因转染骨髓间充质干细胞

目的:研究新型阳离子聚合物Sofast基因转染试剂(Sofast)对大鼠骨髓间充质干细胞(BMSCs)进行基因修饰的可行性.方法:在体外分离和扩增MSCs,在Sofast介导下行pEGFP-N1转染BMSCs,倒置荧光显微镜下观察转染效率及瞬时表达情况,MTT试验检测转染细胞的存活率.结果:增强性绿色荧光蛋白(EGFP)在基因转染24 h后开始表达,48～72 h最高.1周后表达逐渐减弱;质粒与Sofast体积比例为3:1时,pEGFP-N1转染BMSCs的效率为85%,细胞存活率为94.2%.结论:Sofast介导EGFP转染BMSCs是一种较好的转染标记方法.     

Maintenance of pluripotency in human embryonic stem cells stably over-expressing enhanced green fluorescent protein

The availability of human embryonic stem (HES) cells with a readily evaluated genetic marker such as green fluorescent protein (GFP) could facilitate a number of experimental opportunities. We constructed a novel plasmid with two elongation factor-1alpha (EF-1alpha) promoters (YPL2) to obtain a vector with mammalian promoters for simultaneous transgene expression in HES cells. An enhanced green fluorescent protein (EGFP) cDNA was inserted under the control of the first EF-1alpha promoter to construct plasmid YPL2-EGFP. The second EF1-alpha promoter was upstream of the neomycin resistance gene. H1 HES cells were transfected with YPL2-EGFP using Fugene 6. Following 100 microg/ml neomycin selection, individual colonies demonstrating stable EGFP expression were observed. After 4 months of passage under neomycin selection, the cells continued to maintain typical HES cell morphology. Undifferentiated cells showed no change in EGFP expression as determined by FACS analysis. Immunostaining demonstrated maintenance of Oct-3/4 expression in undifferentiated H1EGFP cells that was indistinguishable from wild-type HES cells. Addition of 10 ng/ml bone morphogenic protein-4 (BMP-4) to the cells provoked morphological and functional differentiation to trophoblasts, but no loss of EGFP expression. Following injection of EGFP-HES cells into immunodeficient mice, there was robust formation of teratomas that demonstrated a broad range of morphological pluripotency with widespread EGFP expression. EGFP expression was also maintained in differentiating embryoid bodies formed from EGFP-HES cells. This report demonstrates that ES cells carrying EGFP will be useful in diverse areas of embryonic stem cell research.     

绿色荧光蛋白标记成人骨髓间充质干细胞的超微结构特征

背景：研究表明,绿色荧光蛋白标记的骨髓间充质干细胞免疫学表型、细胞周期、分化潜能等均未发生明显改变。 目的：进一步观察绿色荧光蛋白标记对骨髓间充质干细胞超微结构的影响。 方法：分离培养成人骨髓间充质干细胞,抗CD34、抗CD105免疫细胞化学染色鉴定,选第3代细胞进行绿色荧光蛋白标记,超薄切片后用透射电镜观察细胞超微结构,以未经绿色荧光蛋白标记骨髓间充质干细胞为对照。 结果与结论：骨髓间充质干细胞表达CD105,不表达CD34。绿色荧光蛋白标记后,骨髓间充质干细胞细胞质发出绿色荧光,绿色荧光主要集中于细胞核周围的胞浆内,远离细胞核的胞浆内荧光强度逐渐减弱。相对于未标记的骨髓间充质细胞,经绿色荧光蛋白标记后细胞粗面内质网、高尔基体等细胞器较多,而线粒体相对较少;另外,脂滴和“空泡”样结构也多一些。结果证实绿色荧光蛋白对骨髓间充质干细胞性状的影响较为局限,是一种较为理想的细胞标记示踪剂。     

A histological survey of green fluorescent protein expression in 'green' mice: implications for stem cell research

AIMS: The transgenic enhanced green fluorescent protein (EGFP) expressing 'green' mouse (C57BL/6-TgN(ACTbEGFP)1Osb) is a widely used tool in stem cell research, where the ubiquitous nature of EGFP expression is critical to track the fate of single or small groups of transplanted haematopoietic stem cells (HSC). Our aim was to investigate this assumed ubiquitous expression by performing a detailed histological survey of EGFP expression in these mice. METHODS: Fluorescent microscopy of frozen tissue sections was used to perform a detailed histological survey of the pattern of EGFP expression in these mice. Flow cytometry was also used to determine the expression pattern in blood and bone marrow. RESULTS: Three patterns of EGFP expression were noted. In most tissues there was an apparently stochastic variegation of the transgene, with individual cell types demonstrating highly variable rates of EGFP expression. Certain specific cell types such as pancreatic ductal epithelium, cerebral cortical neurones and glial cells and glomerular mesangial cells consistently lacked EGFP expression, while others, including pancreatic islet cells, expressed EGFP only at extremely low levels, barely distinguishable from background. Lastly, in the colon and stomach the pattern of EGFP expression was suggestive of clonal inactivation. Only cardiac and skeletal muscle showed near ubiquitous expression. CONCLUSIONS: These findings raise questions regarding the 'ubiquitous' expression of EGFP in these transgenic mice and suggest caution in relying overly on EGFP alone as an infallible marker of donor cell origin.     

In vivo and in vitro tissue-specific expression of green fluorescent protein using the cre-lox system in mouse embryonic stem cells

Embryonic stem cells (ES) are pluripotent and may therefore serve as a source for the generation of specific cell types required for future therapies based on cell replacement. The isolation of defined cell populations from a certain lineage or tissue is a prerequisite for the analysis of the potential of such ES-derived cells in animal transplantation studies. Here, using the Cre/loxP system, we report the generation of murine ES cells conditionally expressing the hrGFP gene at the cell surface. Such ES cells can be differentiated in vitro into neurons displaying GFP activity in neurites. Transgenic mice derived from these ES cells permit the targeting of GFP-expression to specific tissues and provide material from the three germ layers suitable for molecular and biochemical analysis.     

Enhanced green fluorescent protein as a marker for localizing murine cytomegalovirus in acute and latent infection

A recombinant murine cytomegalovirus (mCMV) that expresses enhanced green fluorescent protein (EGFP) under control of the native immediate-early 1/3 promoter was constructed to detect directly sites of viral activity in latent and reactivated infections. The recombinant virus had acute and latent infection characteristics similar to those of wild-type mCMV. Rare green-fluorescing foci were observed in paraffin sections from lungs and spleens infected latently. Positive immunoperoxidase staining for EGFP in sections of the same lung tissues suggests that these cells may be sites of restricted viral gene expression. EGFP was detected easily in tissue explants reactivating from latent infection in vitro. Morphology and adhesion characteristics of fluorescing cells suggest that viral reactivation occurs in tissue macrophages in explant cultures. The observations presented in this study demonstrate the usefulness of EGFP-expressing recombinants as tools for direct tracking of mCMV activity in vivo and in vitro.     

The thrombopoietin receptor, c-Mpl, is a selective surface marker for human hematopoietic stem cells

Background  

Thrombopoietin (TPO), the primary cytokine regulating megakaryocyte proliferation and differentiation, exerts significant influence on other hematopoietic lineages as well, including erythroid, granulocytic and lymphoid lineages. We previously demonstrated that the receptor for TPO, c-mpl, is expressed by a subset of human adult bone marrow hematopoietic stem/progenitor cells (HSC/PC) that are enriched for long-term multilineage repopulating ability in the SCID-hu Bone in vivo model of human hematopoiesis.     

绿色荧光蛋白转基因小鼠不同源性间充质干细胞原代培养及生物学特性比较

 目的： 探讨绿色荧光蛋白转基因小鼠脐带和骨髓源性间充质干细胞 （MSCs）的体外分离培养方法、生物学特性、表面标志及多向分化潜能。方法：应用Ⅱ型胶原酶消化培养法分离脐带MSCs及密度梯度离心法分离骨髓MSCs进行体外培养。在倒置显微镜下观察2种细胞的生长特点,运用生长曲线和MTT法检测其原代细胞增殖能力,台盼蓝法测定细胞传代成活率,采用流式细胞术测定2种第3代（P3）细胞DNA周期及表面标志物的表达,并比较其向成脂细胞和成骨细胞的分化潜能。结果：酶消化法分离培养的脐带MSCs 1 d后,细胞贴壁呈成纤维形,2 d后呈漩涡状生长且增殖明显,3 d后达80%融合即可传代;应用密度梯度离心法分离骨髓MSCs,体外培养4 d后,细胞贴壁呈圆形、梭形和多角形生长,5 d后呈克隆样生长且增殖明显,7 d后达80%融合即可传代。原代培养的脐带MSCs生长曲线近似“S”形,骨髓MSCs 生长曲线较平缓;MTT法显示脐带MSCs在3～5 d增殖较明显,骨髓MSCs 7 d后细胞增殖较明显。2种P3细胞传代成活率均为96%以上,G0/G1期细胞均为85%以上,无明显差异（P>0.05）;2种P3细胞CD44、CD90和CD105阳性率均为(60.7±2.3)%以上高表达,CD45、CD19、CD14和CD79a均为(25.6±4.8)%低表达,两者无明显差异（P>0.05）;2种MSCs在体外均具有向成骨细胞和成脂细胞分化的潜能,脐带MSCs向成骨及成脂细胞分化率均为90%以上,与骨髓MSCs的分化潜能比较有显著差异（P<0.05）。结论：脐带MSCs较骨髓MSCs具有较强的增殖能力及分化潜能。绿色荧光蛋白转基因小鼠的脐带MSCs可作为较好干细胞示踪的细胞源。     

Human embryonal carcinoma stem cells expressing green fluorescent protein form functioning neurons in vitro: a research tool for co-culture studies

Neural differentiation is controlled by complex molecular mechanisms that determine cell fate and diversity within the nervous system. Interactions between developing tissues play an important role in regulating this process. In vitro co-culture experiments offer a method to study cell differentiation and function under controlled conditions, with the additional benefit of investigating how interactions between populations of cells influence cell growth and behavior. However, it can often be difficult to distinguish between populations of co-cultured cells. Here we report the development of a human embryonal carcinoma (EC) stem cell line (named TERA2.cl.SP12-GFP) that expresses the genetic marker, green fluorescent protein (GFP). Here, we demonstrate that TERA2.cl.SP12-GFP stem cells stably express GFP and that this remains detectable during retinoic acid-induced differentiation. Regulated expression of neural markers during cell development correlated with the formation of morphologically identifiable neurons. Populations of post-mitotic GFP-positive neurons were readily purified and electrophysiological characterization confirmed that such neurons were functionally active. Thus, cultured TERA2.cl.SP12-GFP cells can be readily distinguished from alternative cell types in vitro and provide an amenable system for live cell imaging to study the development and function of human neurons in isolation, and in co-culture with other tissue types.     

Destabilized green fluorescent protein for monitoring transient changes in mycobacterial gene expression

The green fluorescent protein (GFP) is a useful reporter for the study of gene expression and protein localisation within living cells. The stability of GFP permits its intracellular accumulation and detection, but renders it less useful for assessing transient changes in gene expression. We have developed a destabilized form of GFP for monitoring gene expression in mycobacteria. By fusing to the C-terminal end of GFP an 11 amino acid peptide encoded by the E. coli ssrA gene, we have developed a form of GFP that exhibits gradual, time-dependent degradation within the fast-growing species Mycobacterium smegmatis. This unstable variant of GFP detected transient changes in the activity of the stress-induced Mycobacterium tuberculosis sigE promoter; by contrast, unmodified GFP only detected a delayed 'switch-on' of this promoter upon exposure to acid stress. Both forms of the protein displayed equivalent stability in the slow-growing species Mycobacterium bovis bacille Calmette-Guerin (BCG), suggesting differing recognition of the ssrA-encoded peptides in slow- and fast-growing mycobacteria. This system will facilitate studies exploring dynamic changes in mycobacterial gene expression.