参考文献

Although practiced clinically for more than 40 years,the use of hematopoietic stem cell (HSC) transplants remains limited by the ability to expand these cells ex vivo. An unbiased screen with primary human HSCs identified a purine derivative,StemRegenin 1 (SR1),that promotes the ex vivo expansion of CD34+ cells. Culture of HSCs with SR1 led to a 50-fold increase in cells expressing CD34 and a 17-fold increase in cells that retain the ability to engraft immunodeficient mice. Mechanistic studies show that SR1 acts by antagonizing the aryl hydrocarbon receptor (AHR). The identification of SR1 and AHR modulation as a means to induce ex vivo HSC expansion should facilitate the clinical use of HSC therapy. View Publication

Recent genome-wide association studies (GWASs) have identified a locus on chromosome 1p13 strongly associated with both plasma low-density lipoprotein cholesterol (LDL-C) and myocardial infarction (MI) in humans. Here we show through a series of studies in human cohorts and human-derived hepatocytes that a common noncoding polymorphism at the 1p13 locus,rs12740374,creates a C/EBP (CCAAT/enhancer binding protein) transcription factor binding site and alters the hepatic expression of the SORT1 gene. With small interfering RNA (siRNA) knockdown and viral overexpression in mouse liver,we demonstrate that Sort1 alters plasma LDL-C and very low-density lipoprotein (VLDL) particle levels by modulating hepatic VLDL secretion. Thus,we provide functional evidence for a novel regulatory pathway for lipoprotein metabolism and suggest that modulation of this pathway may alter risk for MI in humans. We also demonstrate that common noncoding DNA variants identified by GWASs can directly contribute to clinical phenotypes. View Publication

Human ESCs are the pluripotent precursor of the three embryonic germ layers. Human ESCs exhibit basal-apical polarity,junctional complexes,integrin-dependent matrix adhesion,and E-cadherin-dependent cell-cell adhesion,all characteristics shared by the epiblast epithelium of the intact mammalian embryo. After disruption of epithelial structures,programmed cell death is commonly observed. If individualized human ESCs are prevented from reattaching and forming colonies,their viability is significantly reduced. Here,we show that actin-myosin contraction is a critical effector of the cell death response to human ESC dissociation. Inhibition of myosin heavy chain ATPase,downregulation of myosin heavy chain,and downregulation of myosin light chain all increase survival and cloning efficiency of individualized human ESCs. ROCK inhibition decreases phosphorylation of myosin light chain,suggesting that inhibition of actin-myosin contraction is also the mechanism through which ROCK inhibitors increase cloning efficiency of human ESCs. View Publication

Human embryonic stem cells (hESCs),unlike mouse ones (mESCs),are vulnerable to apoptosis upon dissociation. Here,we show that the apoptosis,which is of a nonanoikis type,is caused by ROCK-dependent hyperactivation of actomyosin and efficiently suppressed by the myosin inhibitor Blebbistatin. The actomyosin hyperactivation is triggered by the loss of E-cadherin-dependent intercellular contact and also observed in dissociated mouse epiblast-derived pluripotent cells but not in mESCs. We reveal that Abr,a unique Rho-GEF family factor containing a functional Rac-GAP domain,is an indispensable upstream regulator of the apoptosis and ROCK/myosin hyperactivation. Rho activation coupled with Rac inhibition is induced in hESCs upon dissociation,but not in Abr-depleted hESCs or mESCs. Furthermore,artificial Rho or ROCK activation with Rac inhibition restores the vulnerability of Abr-depleted hESCs to dissociation-induced apoptosis. Thus,the Abr-dependent Rho-high/Rac-low" state plays a decisive role in initiating the dissociation-induced actomyosin hyperactivation and apoptosis in hESCs." View Publication

Human embryonic stem cells (hESCs) offer an inexhaustible supply of human somatic cell types through their ability to self-renew while retaining pluripotency. As such,hESC-derived cell types are important for applications ranging from in vitro modeling to therapeutic use. However,for their full potential to be realized,both the growth of the undifferentiated cells and their derivatives must be performed in defined culture conditions. Many research groups maintain hESCs using mouse embryonic fibroblasts (MEF) and MEF conditioned medium (CM). The use of murine systems to support hESCs has been imperative in developing hESC technology; however,they suffer from some major limitations including lack of definition,xenobiotic nature,batch-to-batch variation,and labor-intensive production. Therefore,hESC culture definition is essential if hESC lines,and their derivatives are to be quality assured and manufactured to GMP. We have initiated the process of standardizing hESC tissue culture and have employed two serum-free media: mTeSR (MT) and Stem Pro (SP). hESCs were maintained in a pluripotent state,for over 30 passages using MT and SP. Additionally,we present evidence that hESCs maintained in MT and SP generate equivalent levels of human hepatic endoderm as observed with CM. This data suggests that MT and SP are effective replacements for MEF-CM in hESC culture,contributing to the standardization of hESC in vitro models and ultimately their application. View Publication

Human induced pluripotent stem cells (hiPSCs) provide new possibilities for regenerative therapies. In order for this potential to be achieved,it is critical to efficiently monitor the differentiation of these hiPSCs into specific lineages. Here,we describe a lentiviral reporter vector sensitive to specific microRNAs (miRNA) to show that a single vector bearing multiple miRNA target sequences conjugated to different reporters can be used to monitor hiPSC formation and subsequent differentiation from human fetal fibroblasts (HFFs). The reporter vector encodes EGFP conjugated to the targets of human embryonic stem cell (hESC) specific miRNAs (miR-302a and miR-302d) and mCherry conjugated to the targets of differentiated cells specific miRNAs (miR-142-3p,miR-155,and miR-223). The vector was used to track reprogramming of HFF to iPSC. HFFs co-transduced with this reporter vector and vectors encoding 4 reprogramming factors (OCT4,SOX2,KLF4 and cMYC) were mostly positive for EGFP (67%) at an early stage of hiPSC formation. EGFP expression gradually disappeared and mCherry expression increased indicating less miRNAs specific to differentiated cells and expression of miRNAs specific to hESCs. Upon differentiation of the hiPSC into embryoid bodies,a large fraction of these hiPSCs regained EGFP expression and some of those cells became single positive for EGFP. Further differentiation into neural lineages showed distinct structures demarcated by either EGFP or mCherry expression. These findings demonstrate that a miRNA dependent reporter vector can be a useful tool to monitor living cells during reprogramming of hiPSC and subsequent differentiation to lineage specific cells. View Publication

Human embryonic stem cells (hESC) are expected to provide revolutionary therapeutic applications and drug discovery technologies. In order for this to be achieved a reproducible,defined animal component free culture system is required for the scale-up production of undifferentiated hESC. In this work we have investigated the applicability of a recombinantly produced domain of human vitronectin as an extracellular matrix alternative to the common standards Geltrex or Matrigel. In addition we have validated an ascorbate free media capable of supporting CD30(low) populations of hESC through a multi-factorial analysis of bFGF and Activin A. The recombinant vitronectin domain combined with the ascorbate free media were capable of supporting 3 cell lines,MEL1,MEL2 and hES3 for 10 or more passages while maintaining hESC pluripotency markers and differentiation capacity. The culture method outlined here provides a platform for future investigation into growth factor and extracellular matrix effects on hESC maintenance prior to bioreactor scale-up. View Publication

BACKGROUND AND AIMS: Atherosclerosis is known to be an inflammatory disease and there is increasing evidence that chylomicron remnants (CMR),the lipoproteins which carry dietary fats in the blood,cause macrophage foam cell formation and inflammation. In early atherosclerosis the frequency of activated monocytes in the peripheral circulation is increased,and clearance of CMR from blood may be delayed,however,whether CMR contribute directly to monocyte activation and subsequent egress into the arterial wall has not been established. Here,the contribution of CMR to activation of monocyte pro-inflammatory pathways was assessed using an in vitro model. METHODS AND RESULTS: Primary human monocytes and CMR-like particles (CRLP) were used to measure several endpoints of monocyte activation. Treatment with CRLP caused rapid and prolonged generation of reactive oxygen species by monocytes. The pro-inflammatory chemokines MCP-1 and IL-8 were secreted in nanogram quantities by the cells in the absence of CRLP. IL-8 secretion was transiently increased after CRLP treatment,and CRLP maintained secretion in the presence of pharmacological inhibitors of IL-8 production. In contrast,exposure to CRLP significantly reduced MCP-1 secretion. Chemotaxis towards MCP-1 was increased in monocytes pre-exposed to CRLP and was reversed by addition of exogenous MCP-1. CONCLUSION: Our findings indicate that CRLP activate human monocytes and augment their migration in vitro by reducing cellular MCP-1 expression. Our data support the current hypothesis that CMR contribute to the inflammatory milieu of the arterial wall in early atherosclerosis,and suggest that this may reflect direct interaction with circulating blood monocytes. View Publication

Motor neuron diseases (MNDs) are a group of neurological disorders that selectively affect motor neurons. There are currently no cures or efficacious treatments for these diseases. In recent years,significant developments in stem cell research have been applied to MNDs,particularly regarding neuroprotection and cell replacement. However,a consistent source of motor neurons for cell replacement is required. Human embryonic stem cells (hESCs) could provide an inexhaustible supply of differentiated cell types,including motor neurons that could be used for MND therapies. Recently,it has been demonstrated that induced pluripotent stem (iPS) cells may serve as an alternative source of motor neurons,since they share ES characteristics,self-renewal,and the potential to differentiate into any somatic cell type. In this review,we discuss several reproducible methods by which hESCs or iPS cells are efficiently isolated and differentiated into functional motor neurons,and possible clinical applications. View Publication

BACKGROUND: Therapies directed at augmenting regulatory T cell (Treg) activities in vivo as a systemic treatment for autoimmune disorders and transplantation may be associated with significant off-target effects,including a generalized immunosuppression that may compromise beneficial immune responses to infections and cancer cells. Adoptive cellular therapies using purified expanded Tregs represents an attractive alternative to systemic treatments,with results from animal studies noting increased therapeutic potency of antigen-specific Tregs over polyclonal populations. However,current methodologies are limited in terms of the capacity to isolate and expand a sufficient quantity of endogenous antigen-specific Tregs for therapeutic intervention. Moreover,FOXP3+ Tregs fall largely within the CD4+ T cell subset and are thus routinely MHC class II-specific,whereas class I-specific Tregs may function optimally in vivo by facilitating direct tissue recognition. METHODOLOGY/PRINCIPAL FINDINGS: To overcome these limitations,we have developed a novel means for generating large numbers of antigen-specific Tregs involving lentiviral T cell receptor (TCR) gene transfer into in vitro expanded polyclonal natural Treg populations. Tregs redirected with a high-avidity class I-specific TCR were capable of recognizing the melanoma antigen tyrosinase in the context of HLA-A*0201 and could be further enriched during the expansion process by antigen-specific reactivation with peptide loaded artificial antigen presenting cells. These in vitro expanded Tregs continued to express FOXP3 and functional TCRs,and maintained the capacity to suppress conventional T cell responses directed against tyrosinase,as well as bystander T cell responses. Using this methodology in a model tumor system,murine Tregs designed to express the tyrosinase TCR effectively blocked antigen-specific effector T cell (Teff) activity as determined by tumor cell growth and luciferase reporter-based imaging. CONCLUSIONS/SIGNIFICANCE: These results support the feasibility of class I-restricted TCR transfer as a promising strategy to redirect the functional properties of Tregs and provide for a more efficacious adoptive cell therapy. View Publication

Vinculin is a highly conserved actin-binding protein that is localized in integrin-mediated focal adhesion complexes. Although critical roles have been proposed for integrins in hematopoietic stem cell (HSC) function,little is known about the involvement of intracellular focal adhesion proteins in HSC functions. This study showed that the ability of c-Kit(+)Sca1(+)Lin(-) HSCs to support reconstitution of hematopoiesis after competitive transplantation was severely impaired by lentiviral transduction with short hairpin RNA sequences for vinculin. The potential of these HSCs to differentiate into granulocytic and monocytic lineages,to migrate toward stromal cell-derived factor 1α,and to home to the bone marrow in vivo were not inhibited by the loss of vinculin. However,the capacities to form long term culture-initiating cells and cobblestone-like areas were abolished in vinculin-silenced c-Kit(+)Sca1(+)Lin(-) HSCs. In contrast,adhesion to the extracellular matrix was inhibited by silencing of talin-1,but not of vinculin. Whole body in vivo luminescence analyses to detect transduced HSCs confirmed the role of vinculin in long term HSC reconstitution. Our results suggest that vinculin is an indispensable factor determining HSC repopulation capacity,independent of integrin functions. View Publication

There is increasing evidence that breast and other cancers originate from and are maintained by a small fraction of stem/progenitor cells with self-renewal properties. Whether such cancer stem/progenitor cells originate from normal stem cells based on initiation of a de novo stem cell program,by reprogramming of a more differentiated cell type by oncogenic insults,or both remains unresolved. A major hurdle in addressing these issues is lack of immortal human stem/progenitor cells that can be deliberately manipulated in vitro. We present evidence that normal and human telomerase reverse transcriptase (hTERT)-immortalized human mammary epithelial cells (hMECs) isolated and maintained in Dana-Farber Cancer Institute 1 (DFCI-1) medium retain a fraction with progenitor cell properties. These cells coexpress basal (K5,K14,and vimentin),luminal (E-cadherin,K8,K18,or K19),and stem/progenitor (CD49f,CD29,CD44,and p63) cell markers. Clonal derivatives of progenitors coexpressing these markers fall into two distinct types--a K5(+)/K19(-) type and a K5(+)/K19(+) type. We show that both types of progenitor cells have self-renewal and differentiation ability. Microarray analyses confirmed the differential expression of components of stem/progenitor-associated pathways,such as Notch,Wnt,Hedgehog,and LIF,in progenitor cells compared with differentiated cells. Given the emerging evidence that stem/progenitor cells serve as precursors for cancers,these cellular reagents represent a timely and invaluable resource to explore unresolved questions related to stem/progenitor origin of breast cancer. View Publication