Surface antigens of murine hemopoietic stem cells. I. Cross reactivity of antisera against differentiated hemopoietic cells with bone marrow stem cells

A model of multiply marked hemopoietic stem cells proposed by Till (1) has been tested with respect to antisera raised against differentiated murine hemopoietic cells. When absorbed with erythrocytes, antisera against CBA mouse lymph node lymphocytes, thymocytes, peritoneal macrophages and platelets cross-reacted strongly with pluripotent stem cells (CFUs) in bone marrow as determined by inhibition of spleen colony formation in lethally irradiated mice. Absorption of ATS, antimacrophage serum and antiplatelet serum with hemopoietic cells other than those used to prepare the antisera (e.g., ATS with neutrophils and platelets, antimacrophage serum with neutrophils, thymocytes and platelets and antiplatelet serum with neutrophils and thymocytes) did not reduce the activity of these antisera for CFUs whereas absorption with the inoculating cell type greatly reduced anti-stem cell activity. Absorption of these antisera with non-hemopoietic tissues such as brain, kidney, liver and testis in general had little effect on antistem cell activity, although a significant loss of activity was observed following absorption of antiplatelet serum with kidney. The antistem cell activity in ATS, antimacrophage serum and antiplatelet serum does not appear to be caused by antibodies against histocompatibility antigens sine bone marrow stem cells from histoincompatible C57BL and Balb/c mice were also sensitive to antisera against CBA mouse hemopoietic cells. In contrast to these findings, antisera against erythrocytes showed little cross-reactivity with CFUs, indicating that few antigens are held in common between erythrocytes and CFUs. We propose that nucleated hemopoietic cells and platelets retain cell line specific antigens in common with pluripotent stem cells from which they were derived, and that the continued expression of these antigens during differentiation may be involved in the differentiation process.     

Maintenance of an extrachromosomal plasmid vector in mouse embryonic stem cells.

We have constructed and characterized a polyoma virus-based plasmid that is maintained as an autonomously replicating extrachromosomal element (episome) in mouse embryonic stem (ES) cells. Plasmid pMGD20neo contains the polyoma origin of replication harboring a mutated enhancer (PyF101), a modified polyoma early region that encodes the large tumor (T) antigen only, and a gene that confers resistance to G418 (neo). After transfection, the plasmid replicates in ES cells and is maintained as an extrachromosomal element in 15% of G418-resistant clones. Integration of the plasmid DNA is undetectable for at least 28 cell generations. In one clone, the transfected DNA persists unaltered as an episome at 10-30 copies per cell for at least 74 cell generations in the presence of G418. Cells that maintain the autonomously replicating plasmid can efficiently replicate and maintain a second plasmid that carries the polyoma origin of replication. Independent vector-containing ES cell lines showed no significant alteration of the karyotype, and two cell lines yielded several chimeric animals when introduced into blastocysts, suggesting that the presence of an episomal element and expression of polyoma large T do not eliminate the ES cells' ability to populate an embryo. This system offers an efficient means for manipulating and analyzing various aspects of gene expression in ES cells.     

Normal blood cells of anemic genotype in teratocarcinoma-derived mosaic mice

In allophenic (mosaic) mice produced from blastocysts injected with teratocarcinoma stem cells of the OTT 6050 transplant line, an unexpected coat phenotype led to the discovery that the tumor-lineage cells carried the steel gene (Sl(J)/+). Because steel also causes a macrocytic anemia, mosaics comprising both genetically anemic and normal (+/+) cells fortuitously provided a unique opportunity to examine in vivo the etiology of this anemia in light of previous results indicating that the lesion is extrinsic to the erythroid cells. The experiment differs from previous ones, which involved postnatal grafting, in that here hematopoietic stem cells of anemic and normal genotypes coexist throughout all developmental stages, confronted by tissues of the hematopoietic microenvironment that consist partly or solely of genetically normal cells. Therefore, the possibility exists that the anemia might be completely prevented rather than secondarily ameliorated. Moreover, variation in proportion of normal-strain cells in the hematopoietic supporting tissues could serve to "titrate" minimal requirements to promote normal erythropoiesis. Mice with mixed populations of steel- and normal-genotype cells in blood and other tissues were identified by means of independent markers specific for tumor vs. blastocyst strains of origin. The clinical blood picture of these mosaics proved to be indistinguishable from that of normal controls, even when only a small minority of cells in all tissues of one of the animals were genetically normal. Phenotypic blood normalcy was shown, by occurrence of the typical steel anemia among F(1) germ-line progeny of mosaics, not to be due to any change in the capacity of the mutant gene to elicit the anemia. The results from the mosaics thus demonstrate that the primary expression of the steel lesion is indeed in the hematopoietic microenvironment. However, they also reveal that a surprisingly small complement of normal cells there appears to be adequate to prevent this anemia permanently. The hypothesis is advanced that relatively short-range diffusible substances, produced by cells in the microenvironment and required for normal erythropoiesis, may account for the inductive effectiveness of small cell numbers.     

Insulin expressing cells from differentiated embryonic stem cells are not beta cells

Aim/hypothesis Embryonic stem (ES) cells have been proposed as a potential source of tissue for transplantation for the treatment of Type 1 diabetes. However, studies showing differentiation of beta cells from ES cells are controversial. The aim of this study was to characterise the insulin-expressing cells differentiated in vitro from ES cells and to assess their suitability for the treatment of diabetes.Methods ES cell-derived insulin-expressing cells were characterised by means of immunocytochemistry, RT-PCR and functional analyses. Activation of the Insulin I promoter during ES-cell differentiation was assessed in ES-cell lines transfected with a reporter gene. ES cell-derived cultures were transplanted into STZ-treated SCID-beige mice and blood glucose concentrations of diabetic mice were monitored for 3 weeks.Results Insulin-stained cells differentiated from ES cells were devoid of typical beta-cell granules, rarely showed immunoreactivity for C-peptide and were mostly apoptotic. The main producers of proinsulin/insulin in these cultures were neurons and neuronal precursors and a reporter gene under the control of the insulin I promoter was activated in cells with a neuronal phenotype. Insulin was released into the incubation medium but the secretion was not glucose-dependent. When the cultures were transplanted in diabetic mice they formed teratomas and did not reverse the hyperglycaemic state.Conclusions/Interpretation Our studies show that insulin-positive cells in vitro-differentiated from ES cells are not beta cells and suggest that alternative protocols, based on enrichment of ES cell-derived cultures with cells of the endodermal lineage, should be developed to generate true beta cells for the treatment of diabetes.Abbreviations ES Embryonic stem - LIF leukemia inhibitory factor - ITSF insulin-transferrin-selenite-fibronectin.Bleackley and Korbutt laboratories contributed equally to this paper     

EGFR及ADAM9在胰腺癌干细胞与分化细胞中的表达及意义

目的 通过微球体培养富集胰腺癌干细胞,检测其表皮生长因子受体(EGFR)和去整合素-金属蛋白酶9(ADAM9)的表达,并探讨其意义.方法 运用无血清条件培养基悬浮培养胰腺癌PANC1细胞,并连续传代培养.将部分微球体接种于含血清及胶原底物的培养基中进行分化诱导.收集微球体细胞及分化细胞,流式细胞仪检测侧群(SP)细胞比例;实时PCR及蛋白质印迹法检测细胞EGFR、ADAM9 mRNA和蛋白的表达.结果 成功培养出胰腺癌PANC1细胞微球体,并能在体外连续传代.微球体细胞分化诱导后能重新贴壁生长.微球体细胞和分化细胞中SP细胞比例分别为(5.40±0.38)%和(2.80±0.42)%,两者差异具有统计学意义(P＜0.05).微球体细胞与分化细胞相比,EGFR及ADAM9 mRNA表达分别上调约2.5和3.0倍(P＜0.05);微球体细胞EGFR及ADAM9蛋白相对表达量分别为0.90±0.09和0.64±0.07,显著高于分化细胞的0.62±0.11和0.48±0.09(P＜0.05).结论 微球体培养能富集胰腺癌干细胞,ADAM9可能通过EGFR信号通路在胰腺癌的发生、发展中起重要作用.     

Mosaic mice with teratocarcinoma-derived mutant cells deficient in hypoxanthine phosphoribosyltransferase

Mutagenized stem cells of a cultured mouse teratocarcinoma cell line were selected for resistance to the purine base analog 6-thioguanine. Cells of a resistant clone were completely deficient in activity of the enzyme hypoxanthine phosphoribosyltransferase (HPRT, IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8), the same X-linked lesion as occurs in human Lesch-Nyhan disease. After microinjection into blastocysts of another genetic strain, the previously malignant cells successfully participated in normal embryogenesis and tumor-free, viable mosaic mice were obtained. Cells of tumor lineage were identified by strain markers in virtually all tissues of some individuals. Mature function of those cells was evident from their tissue-specific products (e.g., melanins, liver proteins). These mutagenized teratocarcinoma cells are therefore developmentally totipotent. Retention of the severe HPRT deficiency in the differentiated state was documented in extracts of mosaic tissues by depressed specific activity of the enzyme, and also by presence of unlabeled clones in autoradiographs of explanted cells incubated in [(3)H]hypoxanthine. Some mosaic individuals had mutant-strain cells in only one or a few tissues. Such animals may provide unique opportunities to identify the tissue sources of particular aspects of the complex disease syndrome. The tissue distribution of HPRT-deficient cells suggests that selection against them is particularly strong in blood of the mosaic mice, as is already known to be the case in human heterozygotes. This phenotypic parallelism supports the expectation that afflicted F(1) male mice that might be obtained from mutant germ cells can serve as a model of the human disease.     

HLA expression and immunologic properties of differentiated and undifferentiated mesenchymal stem cells

OBJECTIVE: Mesenchymal stem cells (MSC) do not elicit alloreactive lymphocyte responses due to immune modulations. We investigated the immunologic properties of MSC after differentiation along three lineages: bone, cartilage, and adipose. METHODS AND RESULTS: Flow cytometry showed that undifferentiated MSC express HLA class I but not class II, although HLA class II was present intracellularly as detected by Western blot. Addition of interferon gamma (IFN-gamma) for 48 hours induced greater than 90% of cells to express HLA class II. No lymphocyte response was induced by allogeneic irradiated MSC as stimulators. Results were similar using MSC pretreated with IFN-gamma. After growth of cells in medium to induce differentiation to bone, cartilage, or adipose for 6 or 12 days, the expression of HLA class I increased but no class II was detected on the cell surface. The ability to upregulate HLA class II on the cell surface after exposure to IFN-gamma for 48 hours was clearly diminished after the cells had been cultured in differentiation medium for 6 or 12 days, with only 10% of cells expressing HLA class II. Using MSC grown in osteogenic, chondrogenic, or adipogenic medium as stimulator cells, no lymphocyte alloreactivity was seen, even if differentiated MSC had been pretreated with IFN-gamma. MSC inhibit mixed lymphocyte cultures, particularly after osteogenic differentiation. This suppression was further enhanced by IFN-gamma. CONCLUSIONS: Undifferentiated and differentiated MSC do not elicit alloreactive lymphocyte proliferative responses and modulate immune responses. The findings support that MSC can be transplantable between HLA-incompatible individuals.     

Cartilage tissue engineering using differentiated and purified induced pluripotent stem cells

The development of regenerative therapies for cartilage injury has been greatly aided by recent advances in stem cell biology. Induced pluripotent stem cells (iPSCs) have the potential to provide an abundant cell source for tissue engineering, as well as generating patient-matched in vitro models to study genetic and environmental factors in cartilage repair and osteoarthritis. However, both cell therapy and modeling approaches require a purified and uniformly differentiated cell population to predictably recapitulate the physiological characteristics of cartilage. Here, iPSCs derived from adult mouse fibroblasts were chondrogenically differentiated and purified by type II collagen (Col2)-driven green fluorescent protein (GFP) expression. Col2 and aggrecan gene expression levels were significantly up-regulated in GFP+ cells compared with GFP− cells and decreased with monolayer expansion. An in vitro cartilage defect model was used to demonstrate integrative repair by GFP+ cells seeded in agarose, supporting their potential use in cartilage therapies. In chondrogenic pellet culture, cells synthesized cartilage-specific matrix as indicated by high levels of glycosaminoglycans and type II collagen and low levels of type I and type X collagen. The feasibility of cell expansion after initial differentiation was illustrated by homogenous matrix deposition in pellets from twice-passaged GFP+ cells. Finally, atomic force microscopy analysis showed increased microscale elastic moduli associated with collagen alignment at the periphery of pellets, mimicking zonal variation in native cartilage. This study demonstrates the potential use of iPSCs for cartilage defect repair and for creating tissue models of cartilage that can be matched to specific genetic backgrounds.     

体外诱导入骨髓间充质干细胞向肝系细胞分化过程中的基因表达谱变化

目的 应用微阵列分析骨髓间充质干细胞向肝系细胞分化的基因表达变化.方法 收集健康志愿者胸骨骨髓,分离间充质干细胞体外培养,应用HGF+ FGF4诱导分化并鉴定分化细胞;利用微阵列技术筛选骨髓间充质干细胞向肝系细胞分化的有关基因.结果 121条基因表达发生变化,其中89条上调,32条下调.结论 相关基因涉及信号转导、能量代谢、基因转录、蛋白质翻译与合成等.SGK、ApoB、LDLR和CETP等可能在其分化过程中有非常重要的意义.     

大鼠脊髓来源神经干细胞分化的星形胶质细胞亚型观察

目的观察大鼠脊髓来源神经干细胞分化形成星形胶质细胞的亚型。方法用悬浮培养法培养大鼠脊髓来源的神经干细胞,形成神经球后,以免疫荧光法鉴定神经干细胞;胶质纤维酸性蛋白(GFAP)抗体标记星形胶质细胞,观察其星形胶质细胞的亚型。结果神经干细胞分化第7天,观察到星形胶质细胞共有4种亚型,其中胞体延长型占2.39%±0.13%,扁平多角形占32.33%±2.01%,星形占59.88%±3.12%,双极型占5.39%±0.27%。结论大鼠脊髓来源神经干细胞分化成的星形胶质细胞具有多样性,以星形、扁平多角形为主。     

Actin Is the Naturally Occurring Inhibitor of Deoxyribonuclease I

Various tissues and cells in culture contain a specific inhibitor of DNase I (EC 3.1.4.5). In this paper evidence is presented that this inhibitor is actin, one of the major structural proteins of muscle and nonmuscle cells. (a) The inhibitor is a major cellular component constituting 5-10% of the soluble protein. (b) It migrates with actin on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, having a characteristic molecular weight of 42,000. (c) It has an amino-acid composition closely similar to that of actin. (d) The peptide maps of the two proteins are nearly identical. (e) Skeletal muscle actin inhibits the enzymatic activity of DNase I. (f) DNase I-agarose affinity chromatography quantitatively retains purified skeletal muscle actin, and actin, specifically, from high-speed supernatants of whole cell extracts. (g) An antibody to purified inhibitor protein from calf thymus, used in indirect immunofluorescence on cells grown in culture, stains a two-dimensional network of fibers similar to that seen with an actin-specific antibody.The observation that actin can be isolated by DNase-agarose affinity chromatography provides a useful tool for the biochemical study of actin under different physiological conditions.     

Cloning, isolation, and characterization of replication regions of complex plasmid genomes.

EcoRI endonuclease-generated DNA fragments carrying replication regions of the F'lac and R6-5 plasmids have been cloned and isolated, using as a selection vehicle a nonreplicating ampicillin-resistance DNA fragment derived from a Staphylococcus aureus plasmid. Heteroduplex analysis of the constructed plasmid chimeras and the parent replicons has localized the cloned R6-5 replication region to a DNA segment between kilobase pair coordinates 1.0 and 88.0 on the R6-5 map. Physical proximity between the plasmid replication functions and the locus governing plasmid incompatibility has been shown for both parent replicons. The cloning method reported appears to be generally applicable for the identification and isolation of replication regions of a variety of complex genomes.     

DNA-transformed murine teratocarcinoma cells: regulation of expression of simian virus 40 tumor antigen in stem versus differentiated cells.

Thymidine kinase-deficient (TK-; ATP:thymidine 5'-phosphotransferase, EC 2.7.1.21)F9 teratocarcinoma stem cells have been transformed with a recombinant plasmid genome consisting of the pBR322 genome linked to a herpes simplex virus type 1 thymidine kinase gene (HSV-1 tk) and a simian virus 40 (SV40) genome. A clonal line of stem cells was obtained that contains only one copy of plasmid DNA, which is integrated into murine chromosomal DNA through a site on the pBRR322 genome. The HSV-1 tk gene, which is adjacent to the SV40 genome, is expressed in stem cells, whereas SV40 gene expression is not detectable. If differentiation of these stem cells is induced, the differentiated cells express SV40 early gene products. Thus, we have constructed a stem cell which contains a set of genes (SV40), the expression of which is regulated differently in stem and differentiated cells. This cell line could be used to determine the mechanism of suppression of expression of these genes in stem cells.     

大鼠骨髓间充质干细胞培养、鉴定及神经样细胞分化

目的建立稳定的大鼠骨髓间充质干细胞(BMSCs)体外培养、纯化、扩增的实验体系,并进行细胞表面抗原的鉴定及定向诱导分化检测。方法采用全骨髓贴壁培养法分离、纯化大鼠BMSCs;观察细胞形态,采用细胞免疫化学染色及流式细胞术检测细胞表面CD90、CD29、CD34和CD45表达;分别使用β-巯基乙醇及碱性成纤维细胞生长因子诱导细胞向神经样细胞分化,采用Western印迹法检测诱导后神经标志蛋白[神经巢蛋白(Nestin)、神经元特异烯醇化酶(NSE)、胶质纤维酸性蛋白(GFAP)]表达。结果培养至第3代的BMSCs,CD90、CD29表达阳性,CD34和CD45表达阴性;经诱导后,神经标志蛋白表达显著增高(P<0.05)。结论全骨髓贴壁培养法可分离、培养得到高纯度、具备相关生物学特性的BMSCs,且经诱导可定向分化为神经样细胞。     

Correction of factor IX deficiency in mice by embryonic stem cells differentiated in vitro

Murine embryonic stem (ES) cells are pluripotent, but significant functional engraftment does not occur when they are introduced into the liver. However, here we demonstrate that functional liver engraftment does occur if the ES cells (from strain 129 mice) are first differentiated in vitro for 7 days in the presence of FGF. Strikingly, when these differentiated cells, termed putative endodermal precursors (PEPs), were injected into their livers, two of six C57BL/6 and four of eight BALB/c factor IX (F-IX)-deficient mice survived for >7 days, even though the recipients were of a different strain and, in the case of the BALB/c recipients, had a complete MHC mismatch. F-IX was detected in all six of the PEP-injected survivors. Two mice subsequently died of causes unrelated to F-IX; the others survived until death at 38 or 115 days after the transplantation. No uninjected control F-IX-deficient mice survived for >7 days. Large confluent regions of sinusoidal PEP engraftment were demonstrated by immunofluorescence in the long-term BALB/c survivors. The PEP engraftment was not associated with detectable cell fusion, and the transplantation was accompanied with only a low incidence of teratoma formation.     

鼠胚胎干细胞早期分化来源的心肌细胞同种异体移植后的电生理特性

目的 探讨小鼠胚胎干细胞早期分化来源的心肌细胞进行同种异体移植后的电生理特性.方法 首先通过电转染构建a-MHC-EGFP-ESc系[将心肌细胞特异的OL-MHC启动子与表达基因--绿色荧光蛋白(EGFP)基因融合,构建成真核表达载体],悬滴法诱导胚胎干细胞分化,在分化早期(7+4)d利用流式细胞仪筛选带绿色荧光的心肌细胞,将纯化的心肌细胞(5×106个/ml)移植到小鼠心室壁,对照组注入等体积培养基,移植前3 d开始应用环孢素A(静脉注射,5 mg·kg-1·d-1)和泼尼松龙(静脉注射,2.5 mg·kg-1·d-1)抑制免疫排斥反应.移植后2周分离两侧颈迷走神经行电刺激抑制窦房结与房室结,记录刺激前后的体表心电图,然后分别行免疫荧光显像和膜片钳研究.结果 刺激迷走神经前,移植组和对照组均呈正常的窦性心律,两组无室性心律失常的发生;刺激迷走神经后,两组动物均出现异位的心室起搏心律,细胞移植组与对照组心室频率无差异.移植区冰冻切片免疫荧光分析可见EGFP标记的移植细胞具有肌钙蛋白I(cTnI)表达,说明分化细胞移植后仍具有心肌特性,且移植细胞与宿主心肌细胞间有连接蛋白43的表达,表明移植细胞与宿主心肌细胞间形成电偶联通道.膜片钳分析,绿色荧光细胞移植前后其具有起搏细胞动作电位的比例分别为(85.1%vs 1 1.4%,P＜0.05),该类细胞在移植前后的起搏电流强度有所增强((11.2±2.4)pA/pF vs(15.5±1.9)pA/pF,P＜0.05].移植区分离的绿色荧光细胞中48%具有心室肌动作电位.结论 胚胎干细胞早期分化来源的心肌细胞在体移植后能进一步分化为成熟的心室肌细胞及起搏细胞.     

鼠胚胎干细胞体外分化的单个心肌细胞获取方法

用鼠胚胎干细胞在体外分化成心肌细胞是研究心肌细胞进化和生理学实验的新途径 ,胚胎干细胞最初是从鼠胚胎在胚泡阶段或 8个细胞的胚胎阶段的内部没分化的细胞中得到。其可以定向诱导分化为几乎所有种类的细胞 ,此文介绍了由鼠胚胎干细胞分化成为心肌细胞及单个心肌细胞的获取方法。