参考文献

Recent genomic approaches have revealed that the repertoire of RNA Pol III-transcribed genes varies in different human cell types,and that this variation is likely determined by a combination of the chromatin landscape,cell-specific DNA-binding transcription factors,and collaboration with RNA Pol II. Although much is known about this regulation in differentiated human cells,there is presently little understanding of this aspect of the Pol III system in human ES cells. Here,we determine the occupancy profiles of Pol III components in human H1 ES cells,and also induced pluripotent cells,and compare to known profiles of chromatin,transcription factors,and RNA expression. We find a relatively large fraction of the Pol III repertoire occupied in human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs). In ES cells we find clear correlations between Pol III occupancy and active chromatin. Interestingly,we find a highly significant fraction of Pol III-occupied genes with adjacent binding events by pluripotency factors in ES cells,especially NANOG. Notably,in human ES cells we find H3K27me3 adjacent to but not overlapping many active Pol III loci. We observe in all such cases,a peak of H3K4me3 and/or RNA Pol II,between the H3K27me3 and Pol III binding peaks,suggesting that H3K4me3 and Pol II activity may “insulate�? Pol III from neighboring repressive H3K27me3. Further,we find iPSCs have a larger Pol III repertoire than their precursors. Finally,the active Pol III genome in iPSCs is not completely reprogrammed to a hESC like state and partially retains the transcriptional repertoire of the precursor. Together,our correlative results are consistent with Pol III binding and activity in human ES cells being enabled by active/permissive chromatin that is shaped in part by the pluripotency network of transcription factors and RNA Pol II activity. View Publication

Lack of robust methods for establishment and expansion of pluripotent human embryonic stem (hES) cells still hampers development of cell therapy. Laminins (LN) are a family of highly cell-type specific basement membrane proteins important for cell adhesion,differentiation,migration and phenotype stability. Here we produce and isolate a human recombinant LN-521 isoform and develop a cell culture matrix containing LN-521 and E-cadherin,which both localize to stem cell niches in vivo. This matrix allows clonal derivation,clonal survival and long-term self-renewal of hES cells under completely chemically defined and xeno-free conditions without ROCK inhibitors. Neither LN-521 nor E-cadherin alone enable clonal survival of hES cells. The LN-521/E-cadherin matrix allows hES cell line derivation from blastocyst inner cell mass and single blastomere cells without a need to destroy the embryo. This method can facilitate the generation of hES cell lines for development of different cell types for regenerative medicine purposes. View Publication

The key regulators of endothelial differentiation that is induced by shear stress are mostly unclear. Human atonal homolog 6 (Hath6 or ATOH8) is an endothelial-selective and shear-stress-responsive transcription factor. In this study,we sought to elucidate the role of Hath6 in the endothelial specification of embryonic stem cells. In a stepwise human embryonic stem cell to endothelial cell (hESC-EC) induction system,Hath6 mRNA was upregulated synchronously with endothelial determination. Subsequently,gain-of-function and loss-of-function studies of Hath6 were performed using the hESC-EC induction model and endothelial cell lines. The overexpression of Hath6,which mimics shear stress treatment,resulted in an increased CD45(-)CD31(+)KDR(+) population,a higher tubular-structure-formation capacity and increased endothelial-specific gene expression. By contrast,the knockdown of Hath6 mRNA markedly decreased endothelial differentiation. Hath6 also facilitated the maturation of endothelial cells in terms of endothelial gene expression,tubular-structure formation and cell migration. We further demonstrated that the gene encoding eNOS is a direct target of Hath6 through a reporter system assay and western blot analysis,and that the inhibition of eNOS diminishes hESC-EC differentiation. These results suggest that eNOS plays a key role in linking Hath6 to the endothelial phenotype. Further in situ hybridization studies in zebrafish and mouse embryos indicated that homologs of Hath6 are involved in vasculogenesis and angiogenesis. This study provides the first confirmation of the positive impact of Hath6 on human embryonic endothelial differentiation and function. Moreover,we present a potential signaling pathway through which shear stress stimulates endothelial differentiation. View Publication

The purpose of this study was to investigate the chondrogenic features of human induced pluripotent stem cells (hiPSCs) and examine the differences in the chondrogenesis between hiPSCs and human bone marrow-derived MSCs (hBMMSCs). Embryoid bodies (EBs) were formed from undifferentiated hiPSCs. After EBs were dissociated into single cells,chondrogenic culture was performed in pellets and alginate hydrogel. Chondro-induced hiPSCs were implanted in osteochondral defects created on the patellar groove of immunosuppressed rats and evaluated after 12 weeks. The ESC markers NANOG,SSEA4 and OCT3/4 disappeared while the mesodermal marker BMP-4 appeared in chondro-induced hiPSCs. After 21 days of culture,greater glycosaminoglycan contents and better chondrocytic features including lacuna and abundant matrix formation were observed from chondro-induced hiPSCs compared to chondro-induced hBMMSCs. The expression of chondrogenic markers including SOX-9,type II collagen,and aggrecan in chondro-induced hiPSCs was comparable to or greater than chondro-induced hBMMSCs. A remarkably low level of hypertrophic and osteogenic markers including type X collagen,type I collagen and Runx-2 was noted in chondro-induced hiPSCs compared to chondro-induced hBMMSCs. hiPSCs had significantly greater methylation of several CpG sites in COL10A1 promoter than hBMMSCs in either undifferentiated or chondro-induced state,suggesting an epigenetic cause of the difference in hypertrophy. The defects implanted with chondro-induced hiPSCs showed a significantly better quality of cartilage repair than the control defects,and the majority of cells in the regenerated cartilage consisted of implanted hiPSCs. ?? 2014 Elsevier Ltd. View Publication

Following haematopoietic stem cell transplantation,monitoring the proportion of donor and recipient haematopoiesis in the patient (chimerism) is an influential tool in directing further treatment choices. Short tandem repeat (STR) analysis is a method of chimerism monitoring using DNA isolated from peripheral blood,bone marrow or specific isolated cell lineages such as CD3+ T cells. For lineage-specific STR analysis on cell populations isolated from peripheral blood,a qualitative estimation of the purity of each isolated population is essential for the correct interpretation of the test data. We describe a rapid,inexpensive method for the determination of purity using a simple flow cytometry method. The method described for assessing the purity of sorted CD3+ cells can be applied to any cell population isolated using the same technology. Data obtained were comparable to results from a commercial polymerase chain reaction (PCR)-based method for the assessment of purity (Non-T Genomic Detection Kit,Accumol,Calgary,AB,Canada) (P = 0.59). Of the 303 samples tested by flow cytometry,290 (95.7%) exceeded 90% purity,and 215 (70.95%) were over 99% pure. There were some outlying samples,showing diversity between samples and the unpredictability of purity of isolated cell populations. This flow cytometry method can be easily assimilated into routine testing protocols,allowing purity assessment in multiple-sorted cell populations for lineage-specific chimerism monitoring using a single secondary antibody and giving results comparable to a PCR-based method. As purity of isolated cell lineages is affected by time after venepuncture and storage temperature,assessment of each sample is recommended to give a reliable indication of sample quality and confidence in the interpretation of the results. View Publication

Human cell transformation is a key step for oncogenic development,which involves multiple pathways; however,the mechanism remains unclear. To test our hypothesis whether cell oncogenic transformation shares some mechanisms with the process of reprogramming non-stem cells to induced pluripotent stem cells (iPSC),we studied the relationship among the key factors for promoting or inhibiting iPSC in radiation-transformed human epithelial cell lines derived from different tissues (lung,breast and colon). We unexpectedly found that p63 and OCT4 were highly expressed (accompanied by low expressed p53 and miR-34a) in all transformed cell lines examined when compared with their non-transformed counterparts. We further elucidated the relationship of these factors: the 3p strand of miR-34a directly targeted OCT4 by binding to the 3′ untranslated region (3′-UTR) of OCT4 and,OCT4,in turn,stimulated p63 but inhibited p53 expression by binding to a specific region of the p63 or p53 promoter. Moreover,we revealed that the effects of OCT4 on promoting cell oncogenic transformation were by affecting p63 and p53. These results support that a positive loop exists in human cells: OCT4 upregulation as a consequence of inhibition of miR-34a,promotes p63 but suppresses p53 expression,which further stimulates OCT4 upregulation by downregulating miR-34a. This functional loop contributes significantly to cell transformation and,most likely,also to the iPSC process. View Publication

INTRODUCTION: Upregulation of PI3K/Akt/mTOR signalling in endocrine-resistant breast cancer (BC) has identified mTOR as an attractive target alongside anti-hormones to control resistance. RAD001 (everolimus/Afinitor®),an allosteric mTOR inhibitor,is proving valuable in this setting; however,some patients are inherently refractory or relapse during treatment requiring alternative strategies. Here we evaluate the potential for novel dual mTORC1/2 mTOR kinase inhibitors,exemplified by AZD8055,by comparison with RAD001 in ER + endocrine resistant BC cells. METHODS: In vitro models of tamoxifen (TamR) or oestrogen deprivation resistance (MCF7-X) were treated with RAD001 or AZD8055 alone or combined with anti-hormone fulvestrant. Endpoints included growth,cell proliferation (Ki67),viability and migration,with PI3K/AKT/mTOR signalling impact monitored by Western blotting. Potential ER cross-talk was investigated by immunocytochemistry and RT-PCR. RESULTS: RAD001 was a poor growth inhibitor of MCF7-derived TamR and MCF7-X cells (IC50 ≥1 μM),rapidly inhibiting mTORC1 but not mTORC2/AKT signalling. In contrast AZD8055,which rapidly inhibited both mTORC1 and mTORC2/AKT activity,was a highly effective (P textless0.001) growth inhibitor of TamR (IC50 18 nM) and MCF7-X (IC50 24 nM),and of a further T47D-derived tamoxifen resistant model T47D-tamR (IC50 19 nM). AZD8055 significantly (P textless0.05) inhibited resistant cell proliferation,increased cell death and reduced migration. Furthermore,dual treatment of TamR or MCF7-X cells with AZD8055 plus fulvestrant provided superior control of resistant growth versus either agent alone (P textless0.05). Co-treating with AZD8055 alongside tamoxifen (P textless0.01) or oestrogen deprivation (P textless0.05) also effectively inhibited endocrine responsive MCF-7 cells. Although AZD8055 inhibited oestrogen receptor (ER) ser167 phosphorylation in TamR and MCF7-X,it had no effect on ER ser118 activity or expression of several ER-regulated genes,suggesting the mTOR kinase inhibitor impact was largely ER-independent. The capacity of AZD8055 for ER-independent activity was further evidenced by growth inhibition (IC5018 and 20 nM) of two acquired fulvestrant resistant models lacking ER. CONCLUSIONS: This is the first report demonstrating dual mTORC1/2 mTOR kinase inhibitors have potential to control acquired endocrine resistant BC,even under conditions where everolimus fails. Such inhibitors may prove of particular benefit when used alongside anti-hormonal treatment as second-line therapy in endocrine resistant disease,and also potentially alongside anti-hormones during the earlier endocrine responsive phase to hinder development of resistance. View Publication

The first step in developing regenerative medicine approaches to treat renal diseases using pluripotent stem cells must be the generation of intermediate mesoderm (IM),an embryonic germ layer that gives rise to kidneys. In order to achieve this goal,establishing an efficient,stable and low-cost method for differentiating IM cells using small molecules is required. In this study,we identified two retinoids,AM580 and TTNPB,as potent IM inducers by high-throughput chemical screening,and established rapid (five days) and efficient (80% induction rate) IM differentiation from human iPSCs using only two small molecules: a Wnt pathway activator,CHIR99021,combined with either AM580 or TTNPB. The resulting human IM cells showed the ability to differentiate into multiple cell types that constitute adult kidneys,and to form renal tubule-like structures. These small molecule differentiation methods can bypass the mesendoderm step,directly inducing IM cells by activating Wnt,retinoic acid (RA),and bone morphogenetic protein (BMP) pathways. Such methods are powerful tools for studying kidney development and may potentially provide cell sources to generate renal lineage cells for regenerative therapy. View Publication

UNLABELLED Congenital human cytomegalovirus (HCMV) infection is a major cause of central nervous system structural anomalies and sensory impairments. It is likely that the stage of fetal development,as well as the state of differentiation of susceptible cells at the time of infection,affects the severity of the disease. We used human embryonic stem (ES) cell-derived primitive prerosette neural stem cells (pNSCs) and neural progenitor cells (NPCs) maintained in chemically defined conditions to study HCMV replication in cells at the early stages of neural development. In contrast to what was observed previously using fetus-derived NPCs,infection of ES cell-derived pNSCs with HCMV was nonprogressive. At a low multiplicity of infection,we observed only a small percentage of cells expressing immediate-early genes (IE) and early genes. IE expression was found to be restricted to cells negative for the anterior marker FORSE-1,and treatment of pNSCs with retinoic acid restored IE expression. Differentiation of pNSCs into NPCs restored IE expression but not the transactivation of early genes. Virions produced in NPCs and pNSCs were exclusively cell associated and were mostly non-neural tropic. Finally,we found that viral genomes could persist in pNSC cultures for up to a month after infection despite the absence of detectable IE expression by immunofluorescence,and infectious virus could be produced upon differentiation of pNSCs to neurons. In conclusion,our results highlight the complex array of hurdles that HCMV must overcome in order to infect primitive neural stem cells and suggest that these cells might act as a reservoir for the virus. IMPORTANCE Human cytomegalovirus (HCMV) is a betaherpesvirus that is highly prevalent in the population. HCMV infection is usually asymptomatic but can lead to severe consequences in immunosuppressed individuals. HCMV is also the most important infectious cause of congenital developmental birth defects. Manifestations of fetal HCMV disease range from deafness and learning disabilities to more severe symptoms such as microcephaly. In this study,we have used embryonic stem cells to generate primitive neural stem cells and have used these to model HCMV infection of the fetal central nervous system (CNS) in vitro. Our results reveal that these cells,which are similar to those present in the developing neural tube,do not support viral replication but instead likely constitute a viral reservoir. Future work will define the effect of viral persistence on cellular functions as well as the exogenous signals leading to the reactivation of viral replication in the CNS. View Publication

SIRT1,an NAD-dependent deacetylase,plays a role in regulation of autophagy. SIRT1 increases mitochondrial function and reduces oxidative stress,and has been linked to age-related reactive oxygen species (ROS) generation,which is highly dependent on mitochondrial metabolism. H2O2 induces oxidative stress and autophagic cell death through interference with Beclin 1 and the mTOR signaling pathways. We evaluated connections between SIRT1 activity and induction of autophagy in murine (m) and human (h) embryonic stem cells (ESCs) upon ROS challenge. Exogenous H2O2 (1 mM) induced apoptosis and autophagy in wild-type (WT) and Sirt1-/- mESCs. High concentrations of H2O2 (1 mM) induced more apoptosis in Sirt1-/-,than in WT mESCs. However,addition of 3-methyladenine,a widely used autophagy inhibitor,in combination with H2O2 induced more cell death in WT than in Sirt1-/- mESCs. Decreased induction of autophagy in Sirt1-/- mESCs was demonstrated by decreased conversion of LC3-I to LC3-II,lowered expression of Beclin-1,and decreased LC3 punctae and LysoTracker staining. H2O2 induced autophagy with loss of mitochondrial membrane potential and disruption of mitochondrial dynamics in Sirt1-/- mESCs. Increased phosphorylation of P70/85-S6 kinase and ribosomal S6 was noted in Sirt1-/- mESCs,suggesting that SIRT1 regulates the mTOR pathway. Consistent with effects in mESCs,inhibition of SIRT1 using Lentivirus-mediated SIRT1 shRNA in hESCs demonstrated that knockdown of SIRT1 decreased H2O2-induced autophagy. This suggests a role for SIRT1 in regulating autophagy and mitochondria function in ESCs upon oxidative stress,effects mediated at least in part by the class III PI3K/Beclin 1 and mTOR pathways. Stem Cells 2014;32:1183-1194 View Publication

BACKGROUND Granulocyte colony-stimulating factor (G-CSF) is a pro-inflammatory cytokine that stimulates myeloid stem cell maturation,proliferation,and migration into circulation. Despite being a known growth factor,the impact of G-CSF on solid tumours has not been well examined. G-CSF receptor (G-CSFR) is expressed by some tumours,and thus the aim of this study was to examine the expression and impact of G-CSF and G-CSFR on gastrointestinal tumours. METHODS In this study,G-CSF expression was examined in human gastric and colon tumours and by tumour-derived stromal myofibroblasts and carcinoma cells. G-CSFR expression was examined on carcinoma cells isolated from human tissues. The effects of G-CSF on gastric and colon carcinoma cell proliferation,migration,and signalling were examined. RESULTS G-CSFR was highly expressed in 90% of human gastric and colon carcinomas. G-CSF was also found to be highly produced by stromal myofibroblasts and carcinoma cells. Exposure of carcinoma cells to G-CSF led to increased proliferation and migration,and expansion of a sub-population of carcinoma cells expressing stem-like markers. These processes were dependent on ERK1/2 and RSK1 phosphorylation. CONCLUSIONS These data suggest that the G-CSF/R axis promotes gastric and colorectal cancer development and suggest they are potential tumour targets. View Publication

The reliable derivation of induced pluripotent stem cells (iPSCs) from a noninvasive autologous source at birth would facilitate the study of patient-specific in vitro modeling of congenital diseases and would enhance ongoing efforts aimed at developing novel cell-based treatments for a wide array of fetal and pediatric disorders. Accordingly,we have successfully generated iPSCs from human fetal chorionic somatic cells extracted from term pregnancies by ectopic expression of OCT4,SOX2,KLF4,and cMYC. The isolated parental somatic cells exhibited an immunophenotypic profile consistent with that of chorionic mesenchymal stromal cells (CMSCs). CMSC-iPSCs maintained pluripotency in feeder-free systems for more than 15 passages based on morphology,immunocytochemistry,and gene expression studies and were capable of embryoid body formation with spontaneous trilineage differentiation. CMSC-iPSCs could be selectively differentiated in vitro into various germ layer derivatives,including neural stem cells,beating cardiomyocytes,and definitive endoderm. This study demonstrates the feasibility of term placental chorion as a novel noninvasive alternative to dermal fibroblasts and cord blood for human perinatal iPSC derivation and may provide additional insights regarding the reprogramming capabilities of extra-embryonic tissues as they relate to developmental ontogeny and perinatal tissue engineering applications. View Publication