技术资料

Ethical and moral issues rule out the use of human induced pluripotent stem cells (iPSCs) in chimera studies that would determine the full extent of their reprogrammed state,instead relying on less rigorous assays such as teratoma formation and differentiated cell types. To date,only mouse iPSC lines are known to be truly pluripotent. However,initial mouse iPSC lines failed to form chimeric offspring,but did generate teratomas and differentiated embryoid bodies,and thus these specific iPSC lines were not completely reprogrammed or truly pluripotent. Therefore,there is a need to address whether the reprogramming factors and process used eventually to generate chimeric mice are universal and sufficient to generate reprogrammed iPSC that contribute to chimeric offspring in additional species. Here we show that porcine mesenchymal stem cells transduced with 6 human reprogramming factors (POU5F1,SOX2,NANOG,KLF4,LIN28,and C-MYC) injected into preimplantation-stage embryos contributed to multiple tissue types spanning all 3 germ layers in 8 of 10 fetuses. The chimerism rate was high,85.3% or 29 of 34 live offspring were chimeras based on skin and tail biopsies harvested from 2- to 5-day-old pigs. The creation of pluripotent porcine iPSCs capable of generating chimeric offspring introduces numerous opportunities to study the facets significantly affecting cell therapies,genetic engineering,and other aspects of stem cell and developmental biology. View Publication

Trib1,Trib2,and Trib3 are mammalian homologs of Tribbles,an evolutionarily conserved Drosophila protein family that mediates protein degradation. Tribbles proteins function as adapters to recruit E3 ubiquitin ligases and enhance ubiquitylation of the target protein to promote its degradation. Increased Trib1 and Trib2 mRNA expression occurs in human myeloid leukemia and induces acute myeloid leukemia in mice,whereas Trib3 has not been associated with leukemia. Given the high degree of structural conservation among Tribbles family members,we directly compared the 3 mammalian Tribbles in hematopoietic cells by reconstituting mice with hematopoietic stem cells retrovirally expressing these proteins. All mice receiving Trib1 or Trib2 transduced hematopoietic stem cells developed acute myeloid leukemia,whereas Trib3 mice did not. Our previous data indicated that Trib2-mediated degradation of the transcription factor,CCAAT/enhancer-binding protein-alpha (C/EBPalpha),is important for leukemogenesis. Similar to Trib2,Trib1 induced C/EBPalpha degradation and inhibited its function. In contrast,Trib3 failed to inactivate or promote efficient degradation of C/EBPalpha. These data reveal that the 3 Tribbles homologs differ in their ability to promote degradation of C/EBPalpha,which account for their differential ability to induce leukemia. View Publication

In somatic cells,eroded telomeres can induce DNA double-strand break signaling,leading to a form of replicative senescence or apoptosis,both of which are barriers to tumorigenesis. However,cancer cells might display telomere dysfunctions which in conjunction with defects in DNA repair and apoptosis,enables them to circumvent these pathways. Chronic lymphocytic leukemia (CLL) cells exhibit telomere dysfunction,and a subset of these cells are resistant to DNA damage-induced apoptosis and display short telomeres. We show here that these cells exhibit significant resection of their protective telomeric 3' single-stranded overhangs and an increased number of telomere-induced foci containing gammaH2AX and 53BP1. Chromatin immunoprecipitation and immunofluorescence experiments demonstrated increased levels of telomeric Ku70 and phospho-S2056-DNA-PKcs,2 essential components of the mammalian nonhomologous end-joining DNA repair system. Notably,these CLL cells display deletions of telomeric signals on one or 2 chromatids in parallel with 11q22 deletions,or with 13q14 deletions associated with another chromosomal aberration or with a complex karyotype. Taken together,our results indicate that a subset of CLL cells from patients with an unfavorable clinical outcome harbor a novel type of chromosomal aberration resulting from telomere dysfunction. View Publication

Although the importance of natural killer (NK) cells in innate immune responses against tumors or viral infections are well documented,their ability to directly recognize pathogens is less well defined. We have recently reported FimH,a bacterial fimbrial protein,as a novel Toll-like receptor (TLR)4 ligand that potently induces antiviral responses. Here,we investigated whether FimH either directly or indirectly can activate human and murine NK cells. We demonstrate that FimH potently activates both human and murine NK cells in vitro to induce cytokines [interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha] and cytotoxicity. Importantly,NK cells directly recognize FimH-expressing pathogens as FimH(+),but not FimH(-),bacteria were able to activate human NK cells. FimH activation of NK cells required TLR4 and MyD88 signaling,as NK cells from both TLR4(-/-) and MyD88(-/-) mice as well as human NK-92 cells,which lack TLR4,were all unresponsive to FimH. In addition,TLR4 neutralization significantly abrogated the response of human NK cells to FimH. Activation of purified NK cells by FimH was independent of lipopolysaccharide (LPS) or other bacterial contaminations. These data demonstrate for the first time that highly purified NK cells directly recognize and respond to FimH via TLR4-MyD88 pathways to aid innate protection against cancer or microbial infections. View Publication

Human mesenchymal stromal cells (hMSCs) have generated significant interest due to their potential use in clinical applications. hMSCs are present at low frequency in vivo,but after isolation can be expanded considerably,generating clinically useful numbers of cells. In this study,we demonstrate the use of a defined embryonic stem cell expansion medium,mTeSR (Stem Cell Technologies),for the expansion of bone-marrow-derived hMSCs. The hMSCs grow at comparable rates,demonstrate tri-lineage differentiation potential,and show similar surface marker profiles (CD29(+),CD44(+),CD49a(+),CD73(+),CD90(+),CD105(+),CD146(+),CD166(+),CD34(-),and CD45(-)) in both the fetal bovine serum (FBS)-supplemented medium and mTeSR. However,expression of early differentiation transcription factors runt-related transcription factor 2,sex-determining region Y box 9,and peroxisome proliferator-activated receptor gamma changed significantly. Both runt-related transcription factor 2 and sex-determining region Y box 9 were upregulated,whereas peroxisome proliferator-activated receptor gamma was downregulated in mTeSR compared with FBS. Although osteogenic and chondrogenic differentiation was comparable in cells grown in mTeSR compared to FBS,adipogenic differentiation was significantly decreased in mTeSR-expanded cells,both in terms of gene expression and absolute numbers of adipocytes. The removal of the FBS from the medium and the provision of a defined medium with disclosed composition make mTeSR a superior study platform for hMSC biology in a controlled environment. Further,this provides a key step toward generating a clinical-grade medium for expansion of hMSCs for clinical applications that rely on osteo- and chondroinduction of MSCs,such as bone repair and cartilage generation. View Publication

Umbilical cord blood (CB) represents a main source of circulating endothelial progenitor cells (cEPCs). In view of their clinical use,in either the autologous or allogeneic setting,cEPCs should likely be expanded from CB kept frozen in CB banks. In this study,we compared the expansion,functional features,senescence pattern over culture,and in vivo angiogenic potential of cEPCs isolated from fresh or cryopreserved CB (cryoCB). cEPCs could be isolated in only 59% of cryoCB compared to 94% for fresh CB,while CB units were matched in terms of initial volume,nucleated and CD34(+) cell number. Moreover,the number of endothelial colony-forming cells was significantly decreased when using cryoCB. Once cEPCs culture was established,the proliferation,migration,tube formation,and acetylated-LDL uptake potentials were similar in both groups. In addition,cEPCs derived from cryoCB displayed the same senescence status and telomeres length as that of cEPCs derived from fresh CB. Karyotypic aberrations were found in cells obtained from both fresh and cryoCB. In vivo,in a hind limb ischemia murine model,cEPCs from fresh and cryoCB were equally efficient to induce neovascularization. Thus,cEPCs isolated from cryoCB exhibited similar properties to those of fresh CB in vitro and in vivo. However,the low frequency of cEPCs colony formation after cryopreservation shed light on the need for specific freezing conditions adapted to cEPCs in view of their future clinical use. View Publication

The cancer stem cell (CSC) theory has been proposed to explain the tumor heterogeneity and carcinogenesis process. Recent studies indicate that aldehyde dehydrogenase (ALDH) activity represents a promising CSC marker. Here,we aimed to determine whether human adenoid cystic carcinoma (AdCC) also follows CSC model by exploring the CSC properties of AdCC cells expressing high level of ALDH activity. Utilizing in-vivo series transplantation assays,we found ALDH(high) AdCC cells were capable of self-renewal and of generating tumors that recapitulate the heterogeneity of the parental tumor. Utilizing in-vitro assay,we found only ALDH(high) AdCC cells have tumorsphere-forming ability in anchorage-independent cultures. Finally,we showed ALDH(high) AdCC cells possess highly invasive capability and are responsible for mediating metastasis. These findings suggest the existence of a developmental hierarchy within human AdCC and further elucidation of the unique survival mechanism of AdCC derived CSC population may provide novel therapeutic strategies to treat AdCC. View Publication

Human embryonic stem cells (hESCs) share an identical genome with lineage-committed cells,yet possess the remarkable properties of self-renewal and pluripotency. The diverse cellular properties in different cells have been attributed to their distinct epigenomes,but how much epigenomes differ remains unclear. Here,we report that epigenomic landscapes in hESCs and lineage-committed cells are drastically different. By comparing the chromatin-modification profiles and DNA methylomes in hESCs and primary fibroblasts,we find that nearly one-third of the genome differs in chromatin structure. Most changes arise from dramatic redistributions of repressive H3K9me3 and H3K27me3 marks,which form blocks that significantly expand in fibroblasts. A large number of potential regulatory sequences also exhibit a high degree of dynamics in chromatin modifications and DNA methylation. Additionally,we observe novel,context-dependent relationships between DNA methylation and chromatin modifications. Our results provide new insights into epigenetic mechanisms underlying properties of pluripotency and cell fate commitment. textcopyright 2010 Elsevier Inc. View Publication

The origins of the epithelial cells participating in the development,tissue homeostasis,and cancer of the human breast are poorly understood. However,emerging evidence suggests a role for adult tissue-specific stem cells in these processes. In a hierarchical manner,these generate the two main mammary cell lineages,producing an increasing number of cells with distinct properties. Understanding the biological characteristics of human breast stem cells and their progeny is crucial in attempts to compare the features of normal stem cells and cancer precursor cells and distinguish these from nonprecursor cells and cells from the bulk of a tumor. A historical overview of research on human breast stem cells in primary tissue and in culture reveals the progress that has been made in this area,whereas a focus on the cell-of-origin and reprogramming that occurs during neoplastic conversion provides insight into the enigmatic way in which human breast cancers are skewed toward the luminal epithelial lineage. View Publication

The development of mature blood cells from hematopoietic stem cells requires coordinated activities of transcriptional networks. Transcriptional repressor growth factor independence 1 (Gfi-1) is required for the development of B cells,T cells,neutrophils,and for the maintenance of hematopoietic stem cell function. However,the mechanisms by which Gfi-1 regulates hematopoiesis and how Gfi-1 integrates into transcriptional networks remain unclear. Here,we provide evidence that Id2 is a transcriptional target of Gfi-1,and repression of Id2 by Gfi-1 is required for B-cell and myeloid development. Gfi-1 binds to 3 conserved regions in the Id2 promoter and represses Id2 promoter activity in transient reporter assays. Increased Id2 expression was observed in multipotent progenitors,myeloid progenitors,T-cell progenitors,and B-cell progenitors in Gfi-1(-/-) mice. Knockdown of Id2 expression or heterozygosity at the Id2 locus partially rescues the B-cell and myeloid development but not the T-cell development in Gfi-1(-/-) mice. These studies demonstrate a role of Id2 in mediating Gfi-1 functions in B-cell and myeloid development and provide a direct link between Gfi-1 and the B-cell transcriptional network by its ability to repress Id2 expression. View Publication

We hypothesized that specific activation of a single retinoic acid receptor-alpha (RARalpha),without direct and concurrent activation of RARbeta and gamma,will inhibit mammary tumor oncogenesis in murine models relevant to human cancer. A total of 50 uniparous mouse mammary tumor virus (MMTV)-neu and 50 nuliparous MMTV-wnt1 transgenic mice were treated with RARalpha agonist (retinobenzoic acid,Am580) that was added to the diet for 40 (neu) and 35 weeks (wnt1),respectively. Among the shared antitumor effects was the inhibition of epithelial hyperplasia,a significant increase (Ptextless0.05) in tumor-free survival and a reduction in tumor incidence and in the growth of established tumors. In both models,the mechanisms responsible for these effects involved inhibition of proliferation and survival pathways,and induction of apoptosis. The treatment was more effective in the MMTV-wnt1 model in which Am580 also induced differentiation,in both in vivo and three-dimensional (3D) cultures. In these tumors Am580 inhibited the wnt pathway,measured by loss of nuclear beta-catenin,suggesting partial oncogene dependence of therapy. Am580 treatment increased RARbeta and lowered the level of RARgamma,an isotype whose expression we linked with tumor proliferation. The anticancer effect of RARalpha,together with the newly discovered pro-proliferative role of RARgamma,suggests that specific activation of RARalpha and inhibition of RARgamma might be effective in breast cancer therapy. View Publication

The endosteal niche is critical for the maintenance of hematopoietic stem cells (HSCs). However,it consists of a heterogeneous population in terms of differentiation stage and function. In this study,we characterized endosteal cell populations and examined their ability to maintain HSCs. Bone marrow endosteal cells were subdivided into immature mesenchymal cell-enriched ALCAM(-)Sca-1(+) cells,osteoblast-enriched ALCAM(+)Sca-1(-),and ALCAM(-)Sca-1(-) cells. We found that all 3 fractions maintained long-term reconstitution (LTR) activity of HSCs in an in vitro culture. In particular,ALCAM(+)Sca-1(-) cells significantly enhanced the LTR activity of HSCs by the up-regulation of homing- and cell adhesion-related genes in HSCs. Microarray analysis showed that ALCAM(-)Sca-1(+) fraction highly expressed cytokine-related genes,whereas the ALCAM(+)Sca-1(-) fraction expressed multiple cell adhesion molecules,such as cadherins,at a greater level than the other fractions,indicating that the interaction between HSCs and osteoblasts via cell adhesion molecules enhanced the LTR activity of HSCs. Furthermore,we found an osteoblastic marker(low/-) subpopulation in ALCAM(+)Sca-1(-) fraction that expressed cytokines,such as Angpt1 and Thpo,and stem cell marker genes. Altogether,these data suggest that multiple subsets of osteoblasts and mesenchymal progenitor cells constitute the endosteal niche and regulate HSCs in adult bone marrow. View Publication