技术资料

Human embryonic stem cells (hESCs) can self-renew and become all three germ layers. Nodal/Activin signaling specifies developmental status in hESCs: moderate Nodal/Activin signaling maintains pluripotency,while enhancement and inhibition promote definitive endoderm (DE) and neuroectoderm (NE) development,respectively. However,how modulation of Nodal/Activin signaling influences developmental competence and commitment toward specific lineages is still unclear. Here,we showed that enhancement of Nodal/Activin signaling for 4 days was necessary and sufficient to upregulate DE markers,while it diminished the upregulation of NE markers by inhibition of Nodal/Activin signaling. This suggests that after 4 days of enhanced Nodal/Activin signaling,hESCs are committed to the DE lineage and have lost competence toward the NE lineage. In contrast,inhibition of Nodal/Activin signaling using LY364947 for 2 days was sufficient to impair competence toward the DE lineage,although cells were still able to activate LEFTY1 and NODAL,direct targets of Nodal/Activin signaling. Expression analyses indicated that the levels of pluripotency regulators NANOG and POU5F1 were significantly diminished by 2 days of LY364947 treatment,although the expression of NANOG,but not POU5F1,was restored immediately upon Activin A treatment. Thus,downregulation of POU5F1 coincided with the abrogation of DE competence caused by inhibition of Nodal/Activin signaling. View Publication

The 2009 H1N1 influenza pandemic was a major international public health crisis which caused considerable morbidity and mortality worldwide. The goal of this study was to produce anti-H1 monoclonal antibodies (MAbs) for improving diagnostic immunological assays and to develop potential immunotherapeutics. Nine MAbs were produced after immunizing mice with recombinant hemagglutinin (HA) protein from A/California/06/09. Two spleenocyte myeloma fusions yielded 1588 hybridoma cultures. After screening the hybridoma culture supernatants for antibody reactivity to rHA,nine clones were selected for further characterization. Cross-reactivity studies of the anti-rHA antibodies against a panel of influenza viruses (H1-H16) revealed eight out of nine MAbs were specific to the pandemic H1 subtype,except for MAb F256G2sc1 which also cross-reacted with H5 subtype virus. All MAbs were of the IgG1κ isotype,except F256G2sc1 which was IgG2aκ. The anti-rHA MAbs had binding affinities to rHA that ranged from a K(D) (disassociation constant) of 1.34×10(-9)M (F255G7sc1) to the weakest affinity of 4.60×10(-8)M (F255G4sc1). Interestingly,in a plaque reduction neutralization assay,all MAbs except F255G3sc1 demonstrated neutralizing ability. Furthermore,all MAbs except F255G3sc1 and F255G9sc1 exhibited anti-hemagglutinin activity against pandemic H1N1 viruses,but not against classical North American swine influenza viruses of the same subtype. Immunofluorescence assay (IFA) demonstrated that all MAbs except F255G1sc1 and F255G3sc1 were able to detect 2009 pandemic H1N1 (2009) virus- infected MDCK cells. The MAbs were also evaluated for potential use in competitive ELISA (cELISA),and with the exception of F255G3sc1,all MAbs showed competitive activity with serum collected from pigs infected with pandemic H1N1 virus (2009). The developed MAbs have demonstrated utility as immunodiagnostic and research reagents,and their neutralizing capabilities also hold potential for designing antiviral drugs against pandemic influenza. View Publication

Inner ear hair cells are specialized sensory cells essential for auditory function. Previous studies have shown that the sensory epithelium is postmitotic,but it harbors cells that can behave as progenitor cells in vitro,including the ability to form new hair cells. Lgr5,a Wnt target gene,marks distinct supporting cell types in the neonatal cochlea. Here,we tested the hypothesis that Lgr5(+) cells are Wnt-responsive sensory precursor cells. In contrast to their quiescent in vivo behavior,Lgr5(+) cells isolated by flow cytometry from neonatal Lgr5(EGFP-CreERT2/+) mice proliferated and formed clonal colonies. After 10 d in culture,new sensory cells formed and displayed specific hair cell markers (myo7a,calretinin,parvalbumin,myo6) and stereocilia-like structures expressing F-actin and espin. In comparison with other supporting cells,Lgr5(+) cells were enriched precursors to myo7a(+) cells,most of which formed without mitotic division. Treatment with Wnt agonists increased proliferation and colony-formation capacity. Conversely,small-molecule inhibitors of Wnt signaling suppressed proliferation without compromising the myo7a(+) cells formed by direct differentiation. In vivo lineage tracing supported the idea that Lgr5(+) cells give rise to myo7a(+) hair cells in the neonatal Lgr5(EGFP-CreERT2/+) cochlea. In addition,overexpression of β-catenin initiated proliferation and led to transient expansion of Lgr5(+) cells within the cochlear sensory epithelium. These results suggest that Lgr5 marks sensory precursors and that Wnt signaling can promote their proliferation and provide mechanistic insights into Wnt-responsive progenitor cells during sensory organ development. View Publication

Differentiation of embryonic stem cells (ESCs) into insulin-producing cells for cell replacement therapy of diabetes mellitus comprises the stepwise recapitulation of in vivo developmental stages of pancreatic organogenesis in an in vitro differentiation protocol. The chemical compounds IDE-1 and (-)-indolactam-V can be used to direct mouse and human ESCs through these stages to form definitive endoderm via an intermediate mesendodermal stage and finally into pancreatic endoderm. Cells of the pancreatic endoderm express the PDX1 transcription factor and contribute to all pancreatic cell types upon further in vitro or in vivo differentiation. Even though this differentiation approach is highly effective and reproducible,it generates heterogeneous populations containing PDX1-expressing pancreatic progenitors amongst other cell types. Thus,a technique to separate PDX1-expressing cells from this mixture is very desirable. Recently it has been reported that PDX1-positive pancreatic progenitors,derived from human embryonic stem cells,express the surface marker CD24. Therefore were subjected mouse and human ESCs to a small molecule differentiation approach and the expression of the surface marker CD24 was monitored in undifferentiated cells,cells committed to the definitive endoderm and cells reminiscent of the pancreatic endoderm. We observed that both mouse and human ESCs expressed CD24 in the pluripotent state,during the whole process of endoderm formation and upon further differentiation towards pancreatic endoderm. Thus CD24 is not a suitable cell surface marker for identification of PDX1-positive progenitor cells. View Publication

Neural differentiation of human embryonic (ES) and induced pluripotent (iPS) stem cell lines has been used for research in early human development,drug discovery,and cell replacement therapies. It is critical to establish generic differentiation protocols to compare the neural specification potential of each individually derived pluripotent stem cell line and identify the efficacious lines for research and therapeutic use. Here,we describe a reproducible and quantitative protocol to assess the neural progenitor (NP) generation of human pluripotent stem cell lines. This method includes a robust and well-defined neural inducing platform for Pax6(+) neural rosette (neuroectodermal cells) generation,propagation,and subsequent differentiation into nestin(+) NPs. A side-by-side comparison under common culture conditions among three human ES cell lines,TE03,TE06,and BG01V,and one iPS cell line,HD02,showed highly variable efficiency in their differentiation into NPs. View Publication

This study evaluated the effects of a mammalian target of mTOR inhibitor everolimus alone or in combination with trastuzumab on stem cells from HER2-overexpressing primary breast cancer cells and the BT474 breast cancer cell line in vitro and in vivo. For the in vitro studies,we sorted ESA(+)CD44(+)CD24(-/low) cells as stem cells from primary breast cancer cells and BT474 cells using flow cytometry. The MTT assay was used to quantify the inhibitory effect of the drugs on total cells and stem cells specifically. Stem cell apoptosis,cell cycle distributions,and their tumorigenicity after treatment were investigated by flow cytometry or soft agar colony formation assays. For the in vivo studies,BALB/c mice were injected with BT474 stem cells,and the different treatments were administered. After necropsy,the expression of Ki67,CD31,AKT1,and phospho-AKT (Thr308) was analyzed by immunohistochemistry. For the in vitro studies,Treatment with everolimus resulted in stem cell growth inhibition in a dose-dependent manner. The combination of everolimus with trastuzumab was more effective at inhibiting cell growth (P textless 0.001) and tumorigenicity (P textless 0.001) compared with single-agent therapy. In addition,an increase in G1 cell cycle arrest and an increased population of cells in early apoptosis were seen in the combination treatment group compared with either of the single-agent groups (P textless 0.01). For the in vivo studies,everolimus plus trastuzumab therapy was much more effective at reducing tumor volume in mice compared with either single agent alone (P textless 0.05). Compared with everolimus alone,the combination of everolimus and trastuzumab reduced the expression of Ki67,AKT1,and phospho-AKT (Thr308) (P textless 0.05). We conclude that everolimus has effective inhibitory effects on HER2-overexpressing stem cells in vitro and vivo. Everolimus plus trastuzumab is a rational combination treatment that may be promising in human clinical trials. View Publication

Embryonic stem cells (ESC) have two main characteristics: they can be indefinitely propagated in vitro in an undifferentiated state and they are pluripotent,thus having the potential to differentiate into multiple lineages. Such properties make ESCs extremely attractive for cell based therapy and regenerative treatment applications. However for its full potential to be realized the cells have to be differentiated into mature and functional phenotypes,which is a daunting task. A promising approach in inducing cellular differentiation is to closely mimic the path of organogenesis in the in vitro setting. Pancreatic development is known to occur in specific stages,starting with endoderm,which can develop into several organs,including liver and pancreas. Endoderm induction can be achieved by modulation of the nodal pathway through addition of Activin A in combination with several growth factors. Definitive endoderm cells then undergo pancreatic commitment by inhibition of sonic hedgehog inhibition,which can be achieved in vitro by addition of cyclopamine. Pancreatic maturation is mediated by several parallel events including inhibition of notch signaling; aggregation of pancreatic progenitors into 3-dimentional clusters; induction of vascularization; to name a few. By far the most successful in vitro maturation of ESC derived pancreatic progenitor cells have been achieved through inhibition of notch signaling by DAPT supplementation. Although successful,this results in low yield of the mature phenotype with reduced functionality. A less studied area is the effect of endothelial cell signaling in pancreatic maturation,which is increasingly being appreciated as an important contributing factor in in-vivo pancreatic islet maturation. The current study explores such effect of endothelial cell signaling in maturation of human ESC derived pancreatic progenitor cells into insulin producing islet-like cells. We report a multi-stage directed differentiation protocol where the human ESCs are first induced towards endoderm by Activin A along with inhibition of PI3K pathway. Pancreatic specification of endoderm cells is achieved by inhibition of sonic hedgehog signaling by Cyclopamine along with retinoid induction by addition of Retinoic Acid. The final stage of maturation is induced by endothelial cell signaling achieved by a co-culture configuration. While several endothelial cells have been tested in the co-culture,herein we present our data with rat heart microvascular endothelial Cells (RHMVEC),primarily for the ease of analysis. View Publication

A major difficulty of producing induced pluripotent stem cells (iPSCs) has been the low efficiency of reprogramming differentiated cells into pluripotent cells. We previously showed that 5% of mouse embryonic fibroblasts (MEFs) were reprogrammed into iPSCs when they were transduced with a fusion gene composed of Oct4 and the transactivation domain of MyoD (called M(3)O),along with Sox2,Klf4 and c-Myc (SKM). In addition,M(3)O facilitated chromatin remodeling of pluripotency genes in the majority of transduced MEFs,including cells that did not become iPSCs. These observations suggested the possibility that more than 5% of cells had acquired the ability to become iPSCs given more favorable culture conditions. Here,we raised the efficiency of making mouse iPSCs with M(3)O-SKM to 26% by culturing transduced cells at low density in serum-free culture medium. In contrast,the efficiency increased from 0.1% to only 2% with the combination of wild-type Oct4 and SKM (OSKM) under the same culture condition. For human iPSCs,M(3)O-SKM achieved 7% efficiency under a similar serum-free culture condition,in comparison to 1% efficiency with OSKM. This study highlights the power of combining the transactivation domain of MyoD with a favorable culture environment. View Publication

Although hematopoiesis is known to originate in a population of very primitive cells with both lymphopoietic and myelopoietic potential,a procedure for enumerating such cells has to date not been available. We now describe a quantitative assay for long-term repopulating stem cells with the potential for reconstituting all hematopoietic lineages. This assay has two key features. The first is the use of competitive repopulation conditions that ensure not only the detection of a very primitive class of hematopoietic stem cells but also the survival of lethally irradiated mice transplanted with very low numbers of such cells. The second is the use of a limiting-dilution experimental design to allow stem cell quantitation. The assay involves transplanting limiting numbers of male test" cells into lethally irradiated syngeneic female recipients together with 1-2 x 10(5) syngeneic female marrow cells whose long-term repopulating ability has been compromised by two previous cycles of marrow transplantation. The proportion of assay recipients whose regenerated hematopoietic tissues are determined to contain greater than or equal to 5% cells of test cell origin (male) greater than or equal to 5 weeks later is then used to calculate the frequency of competitive repopulating units (CRU) in the original male test cell suspension (based on Poisson statistics). Investigation of this assay system has shown that all three potential sources of stem cells (test cells� View Publication

The supply of human hepatic stem cells (hHpSCs) and other hepatic progenitors has been constrained by the limited availability of liver tissues from surgical resections,the rejected organs from organ donation programs,and the need to use cells immediately. To facilitate accessibility to these precious tissue resources,we have established an effective method for serum-free cryopreservation of the cells,allowing them to be stockpiled and stored for use as an off-the-shelf product for experimental or clinical programs. The method involves use of buffers,some serum-free,designed for cryopreservation and further supplemented with hyaluronans (HA) that preserve adhesion mechanisms facilitating postthaw culturing of the cells and preservation of functions. Multiple cryopreservation buffers were found to yield high viabilities (80-90%) of cells on thawing of the progenitor cells. Serum-free CS10 supplemented with 0.05% hyaluronan proved the most effective,both in terms of viabilities of cells on thawing and in yielding cell attachment and formation of expanding colonies of cells that stably maintain the stem/progenitor cell phenotype. Buffers to which 0.05 or 0.1% HAs were added showed cells postthaw to be phenotypically stable as stem/progenitors,as well as having a high efficiency of attachment and expansion in culture. Success correlated with improved expression of adhesion molecules,particularly CD44,the hyaluronan receptor,E-cadherin,β4 integrin in hHpSCs,and β1 integrins in hepatoblasts. The improved methods in cryopreservation offer more efficient strategies for stem cell banking in both research and potential therapy applications. View Publication

Dental pulp is particularly interesting in regenerative medicine because of the accessibility and differentiation potential of the tissue. Dental pulp has an early developmental origin with multi-lineage differentiation potential as a result of its development during childhood and adolescence. However,no study has previously identified the presence of stem cell populations with embryonic-like phenotypes in human dental pulp from the third molar. In the present work,we describe a new population of dental pulp pluripotent-like stem cells (DPPSCs) that were isolated by culture in medium containing LIF,EGF and PDGF. These cells are SSEA4(+),OCT3/4(+),NANOG(+),SOX2(+),LIN28(+),CD13(+),CD105(+),CD34(-),CD45(-),CD90(+),CD29(+),CD73(+),STRO1(+) and CD146(-),and they show genetic stability in vitro based on genomic analysis with a newly described CGH technique. Interestingly,DPPSCs were able to form both embryoid-body-like structures (EBs) in vitro and teratoma-like structures that contained tissues derived from all three embryonic germ layers when injected in nude mice. We examined the capacity of DPPSCs to differentiate in vitro into tissues that have similar characteristics to mesoderm,endoderm and ectoderm layers in both 2D and 3D cultures. We performed a comparative RT-PCR analysis of GATA4,GATA6,MIXL1,NANOG,OCT3/4,SOX1 and SOX2 to determine the degree of similarity between DPPSCs,EBs and human induced pluripotent stem cells (hIPSCs). Our analysis revealed that DPPSCs,hIPSC and EBs have the same gene expression profile. Because DPPSCs can be derived from healthy human molars from patients of different sexes and ages,they represent an easily accessible source of stem cells,which opens a range of new possibilities for regenerative medicine. View Publication

Adult stem-cell therapy holds promise for the treatment of gastrointestinal diseases. Here we describe methods for long-term expansion of colonic stem cells positive for leucine-rich repeat containing G protein-coupled receptor 5 (Lgr5(+) cells) in culture. To test the transplantability of these cells,we reintroduced cultured GFP(+) colon organoids into superficially damaged mouse colon. The transplanted donor cells readily integrated into the mouse colon,covering the area that lacked epithelium as a result of the introduced damage in recipient mice. At 4 weeks after transplantation,the donor-derived cells constituted a single-layered epithelium,which formed self-renewing crypts that were functionally and histologically normal. Moreover,we observed long-term (textgreater6 months) engraftment with transplantation of organoids derived from a single Lgr5(+) colon stem cell after extensive in vitro expansion. These data show the feasibility of colon stem-cell therapy based on the in vitro expansion of a single adult colonic stem cell. View Publication