参考文献

Stem-like cells have been isolated in tumors such as breast,lung,colon,prostate and brain. A critical issue in all these tumors,especially in glioblastoma mutliforme (GBM),is to identify and isolate tumor initiating cell population(s) to investigate their role in tumor formation,progression,and recurrence. Understanding tumor initiating cell populations will provide clues to finding effective therapeutic approaches for these tumors. The neurosphere assay (NSA) due to its simplicity and reproducibility has been used as the method of choice for isolation and propagation of many of this tumor cells. This protocol demonstrates the neurosphere culture method to isolate and expand stem-like cells in surgically resected human GBM tumor tissue. The procedures include an initial chemical digestion and mechanical dissociation of tumor tissue,and subsequently plating the resulting single cell suspension in NSA culture. After 7-10 days,primary neurospheres of 150-200 μm in diameter can be observed and are ready for further passaging and expansion. View Publication

Human embryonic stem cells (hESCs) are pluripotent cell types derived from the inner cell mass of human blastocysts. Recent data indicate that the majority of established female XX hESC lines have undergone X chromosome inactivation (XCI) prior to differentiation,and XCI of hESCs can be either XIST-dependent (class II) or XIST-independent (class III). XCI of female hESCs precludes the use of XX hESCs as a cell-based model for examining mechanisms of XCI,and will be a challenge for studying X-linked diseases unless strategies are developed to reactivate the inactive X. In order to recover nuclei with two active X chromosomes (class I),we developed a reprogramming strategy by supplementing hESC media with the small molecules sodium butyrate and 3-deazaneplanocin A (DZNep). Our data demonstrate that successful reprogramming can occur from the XIST-dependent class II nuclear state but not class III nuclear state. To determine whether these small molecules prevent XCI,we derived six new hESC lines under normoxic conditions (UCLA1-UCLA6). We show that class I nuclei are present within the first 20 passages of hESC derivation prior to cryopreservation,and that supplementation with either sodium butyrate or DZNep preserve class I nuclei in the self-renewing state. Together,our data demonstrate that self-renewal and survival of class I nuclei are compatible with normoxic hESC derivation,and that chemical supplementation after derivation provides a strategy to prevent epigenetic progression and retain nuclei with two active X chromosomes in the self-renewing state. View Publication

The use of nanoparticles in medicine is ever increasing,and it is important to understand their targeted and non-targeted effects. We have previously shown that nanoparticles can cause DNA damage to cells cultured below a cellular barrier without crossing this barrier. Here,we show that this indirect DNA damage depends on the thickness of the cellular barrier,and it is mediated by signalling through gap junction proteins following the generation of mitochondrial free radicals. Indirect damage was seen across both trophoblast and corneal barriers. Signalling,including cytokine release,occurred only across bilayer and multilayer barriers,but not across monolayer barriers. Indirect toxicity was also observed in mice and using ex vivo explants of the human placenta. If the importance of barrier thickness in signalling is a general feature for all types of barriers,our results may offer a principle with which to limit the adverse effects of nanoparticle exposure and offer new therapeutic approaches. View Publication

Human induced pluripotent stem (hiPS) cells have potential uses for drug discovery and cell therapy,including generation of pancreatic β-cells for diabetes research and treatment. In this study,we developed a simple protocol for generating insulin-producing cells from hiPS cells. Treatment with activin A and a GSK3β inhibitor enhanced efficient endodermal differentiation,and then combined treatment with retinoic acid,a bone morphogenic protein inhibitor,and a transforming growth factor-β (TGF-β) inhibitor induced efficient differentiation of pancreatic progenitor cells from definitive endoderm. Expression of the pancreatic progenitor markers PDX1 and NGN3 was significantly increased at this step and most cells were positive for anti-PDX1 antibody. Moreover,several compounds,including forskolin,dexamethasone,and a TGF-β inhibitor,were found to induce the differentiation of insulin-producing cells from pancreatic progenitor cells. By combined treatment with these compounds,more than 10% of the cells became insulin positive. The differentiated cells secreted human c-peptide in response to various insulin secretagogues. In addition,all five hiPS cell lines that we examined showed efficient differentiation into insulin-producing cells with this protocol. View Publication

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To gain insight into the molecular regulation of human heart development,a detailed comparison of the mRNA and miRNA transcriptomes across differentiating human-induced pluripotent stem cell (hiPSC)-derived cardiomyocytes and biopsies from fetal,adult,and hypertensive human hearts was performed. Gene ontology analysis of the mRNA expression levels of the hiPSCs differentiating into cardiomyocytes revealed 3 distinct groups of genes: pluripotent specific,transitional cardiac specification,and mature cardiomyocyte specific. Hierarchical clustering of the mRNA data revealed that the transcriptome of hiPSC cardiomyocytes largely stabilizes 20 days after initiation of differentiation. Nevertheless,analysis of cells continuously cultured for 120 days indicated that the cardiomyocytes continued to mature toward a more adult-like gene expression pattern. Analysis of cardiomyocyte-specific miRNAs (miR-1,miR-133a/b,and miR-208a/b) revealed an miRNA pattern indicative of stem cell to cardiomyocyte specification. A biostatistitical approach integrated the miRNA and mRNA expression profiles revealing a cardiomyocyte differentiation miRNA network and identified putative mRNAs targeted by multiple miRNAs. Together,these data reveal the miRNA network in human heart development and support the notion that overlapping miRNA networks re-enforce transcriptional control during developmental specification. View Publication

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We analyzed the proliferative response of the growth factor-dependent murine cell lines FDCp1,DA1-a,32DC1,Ea3.15,7TD1,BCL1 and of femural bone marrow cells for their sensitivity to various cytokines,viz. rhIL-1 beta,rhTNF,rhIL-2,mIL-3,rmIL-4,rmIL-5,rhIL-6,rhG-CSF and rmGM-CSF. We also tested for IL-1 and TNF-mediated cytokine secretion by several T cell lines and thymocytes. In all T cell systems,IL-1 alpha and IL-1 beta were equally active in the induction of cytokine production,except for the rat/mouse T cell hybridoma PC60. This cell line exhibited a 10-fold difference in specific activity for the induction of cytokine secretion between rhIL-1 alpha and the other human or murine IL-1 species. Furthermore,IL-1 and IL-2 synergistically induced PC60 cells to produce a factor,which was preferentially active on FDCp1-cells,provisionally called FDCp1-growth factor. SDS-PAGE analysis of partially purified FDCp1-GF showed 19 kDa and 24 kDa-associated biological activities. Amino-terminal and internal amino acid sequences of both bands were determined and on this basis,we identified FDCp1-GF as rat GM-CSF. View Publication

The recent development of porcine induced pluripotent stem cells (piPSCs) capable of generating chimeric animals,a feat not previously accomplished with embryonic stem cells or iPSCs in a species outside of rodents,has opened the doors for in-depth study of iPSC tumorigenicity,autologous transplantation,and other key aspects to safely move iPSC therapies to the clinic. The study of iPSC tumorigenicity is critical as previous research in the mouse showed that iPSC-derived chimeras possessed large numbers of tumors,rising significant concerns about the safety of iPSC therapies. Additionally,piPSCs capable of generating germline chimeras could revolutionize the transgenic animal field by enabling complex genetic manipulations (e.g.,knockout or knockin of genes) to produce biomedically important large animal models or improve livestock production. In this study,we demonstrate for the first time in a nonrodent species germline transmission of iPSCs with the live birth of a transgenic piglet that possessed genome integration of the human POU5F1 and NANOG genes. In addition,gross and histological examination of necropsied porcine chimeras at 2,7,and 9 months showed that these animals lacked tumor formation and demonstrated normal development. Tissue samples positive for human POU5F1 DNA showed no C-MYC gene expression,further implicating C-MYC as a cause of tumorigenicity. The development of germline-competent porcine iPSCs that do not produce tumors in young chimeric animals presents an attractive and powerful translational model to study the efficacy and safety of stem cell therapies and perhaps to efficiently produce complex transgenic animals. View Publication

Genetic modification is critically enabling for studies addressing specification and maintenance of cell fate; however,methods for engineering modifications are inefficient. We demonstrate a rapid and efficient recombination system in which an inducible,floxed cre allele replaces itself with an incoming transgene. We target this inducible cassette exchange (ICE) allele to the (HPRT) locus and demonstrate recombination in murine embryonic stem cells (ESCs) and primary cells from derivative ICE mice. Using lentivectors,we demonstrate recombination at a randomly integrated ICE locus in human ESCs. To illustrate the utility of this system,we insert the myogenic regulator,Myf5,into the ICE locus in each platform. This enables efficient directed differentiation of mouse and human ESCs into skeletal muscle and conditional myogenic transdetermination of primary cells cultured in vitro. This versatile tool is thus well suited to gain-of-function studies probing gene function in the specification and reprogramming of cell fate. View Publication