技术资料

In February 2013,zoonotic transmission of a novel influenza A virus of the H7N9 subtype was reported in China. Although at present no sustained human-to-human transmission has been reported,a pandemic outbreak of this H7N9 virus is feared. Since neutralizing antibodies to the hemagglutinin (HA) globular head domain of the virus are virtually absent in the human population,there is interest in identifying other correlates of protection,such as cross-reactive CD8(+) T cells (cytotoxic T lymphocytes [CTLs]) elicited during seasonal influenza A virus infections. These virus-specific CD8(+) T cells are known to recognize conserved internal proteins of influenza A viruses predominantly,but it is unknown to what extent they cross-react with the newly emerging H7N9 virus. Here,we assessed the cross-reactivity of seasonal H3N2 and H1N1 and pandemic H1N1 influenza A virus-specific polyclonal CD8(+) T cells,obtained from HLA-typed study subjects,with the novel H7N9 virus. The cross-reactivity of CD8(+) T cells to H7N9 variants of known influenza A virus epitopes and H7N9 virus-infected cells was determined by their gamma interferon (IFN-γ) response and lytic activity. It was concluded that,apart from recognition of individual H7N9 variant epitopes,CD8(+) T cells to seasonal influenza viruses display considerable cross-reactivity with the novel H7N9 virus. The presence of these cross-reactive CD8(+) T cells may afford some protection against infection with the new virus. View Publication

Down's syndrome (DS),caused by trisomy of human chromosome 21,is the most common genetic cause of intellectual disability. Here we use induced pluripotent stem cells (iPSCs) derived from DS patients to identify a role for astrocytes in DS pathogenesis. DS astroglia exhibit higher levels of reactive oxygen species and lower levels of synaptogenic molecules. Astrocyte-conditioned medium collected from DS astroglia causes toxicity to neurons,and fails to promote neuronal ion channel maturation and synapse formation. Transplantation studies show that DS astroglia do not promote neurogenesis of endogenous neural stem cells in vivo. We also observed abnormal gene expression profiles from DS astroglia. Finally,we show that the FDA-approved antibiotic drug,minocycline,partially corrects the pathological phenotypes of DS astroglia by specifically modulating the expression of S100B,GFAP,inducible nitric oxide synthase,and thrombospondins 1 and 2 in DS astroglia. Our studies shed light on the pathogenesis and possible treatment of DS by targeting astrocytes with a clinically available drug. View Publication

Human induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM)-based assays are emerging as a promising tool for the in vitro preclinical screening of QT interval-prolonging side effects of drugs in development. A major impediment to the widespread use of human iPSC-CM assays is the low throughput of the currently available electrophysiological tools. To test the precision and applicability of the near-infrared fluorescent voltage-sensitive dye 1-(4-sulfanatobutyl)-4-β[2-(di-n-butylamino)-6-naphthyl]butadienylquinolinium betaine (di-4-ANBDQBS) for moderate-throughput electrophysiological analyses,we compared simultaneous transmembrane voltage and optical action potential (AP) recordings in human iPSC-CM loaded with di-4-ANBDQBS. Optical AP recordings tracked transmembrane voltage with high precision,generating nearly identical values for AP duration (AP durations at 10%,50%,and 90% repolarization). Human iPSC-CMs tolerated repeated laser exposure,with stable optical AP parameters recorded over a 30-min study period. Optical AP recordings appropriately tracked changes in repolarization induced by pharmacological manipulation. Finally,di-4-ANBDQBS allowed for moderate-throughput analyses,increasing throughput textgreater10-fold over the traditional patch-clamp technique. We conclude that the voltage-sensitive dye di-4-ANBDQBS allows for high-precision optical AP measurements that markedly increase the throughput for electrophysiological characterization of human iPSC-CMs. View Publication

Human pluripotent stem cells (hPSCs) tend to acquire genomic aberrations in culture,the most common of which is trisomy of chromosome 12. Here we dissect the cellular and molecular implications of this trisomy in hPSCs. Global gene expression analyses reveal that trisomy 12 profoundly affects the gene expression profile of hPSCs,inducing a transcriptional programme similar to that of germ cell tumours. Comparison of proliferation,differentiation and apoptosis between diploid and aneuploid hPSCs shows that trisomy 12 significantly increases the proliferation rate of hPSCs,mainly as a consequence of increased replication. Furthermore,trisomy 12 increases the tumorigenicity of hPSCs in vivo,inducing transcriptionally distinct teratomas from which pluripotent cells can be recovered. Last,a chemical screen of 89 anticancer drugs discovers that trisomy 12 raises the sensitivity of hPSCs to several replication inhibitors. Together,these findings demonstrate the extensive effect of trisomy 12 and highlight its perils for successful hPSC applications. View Publication

Long interspersed element-1 (LINE-1 or L1) retrotransposition induces insertional mutations that can result in diseases. It was recently shown that the copy number of L1 and other retroelements is stable in induced pluripotent stem cells (iPSCs). However,by using an engineered reporter construct over-expressing L1,another study suggests that reprogramming activates L1 mobility in iPSCs. Given the potential of human iPSCs in therapeutic applications,it is important to clarify whether these cells harbor somatic insertions resulting from endogenous L1 retrotransposition. Here,we verified L1 expression during and after reprogramming as well as potential somatic insertions driven by the most active human endogenous L1 subfamily (L1Hs). Our results indicate that L1 over-expression is initiated during the reprogramming process and is subsequently sustained in isolated clones. To detect potential somatic insertions in iPSCs caused by L1Hs retotransposition,we used a novel sequencing strategy. As opposed to conventional sequencing direction,we sequenced from the 3' end of L1Hs to the genomic DNA,thus enabling the direct detection of the polyA tail signature of retrotransposition for verification of true insertions. Deep coverage sequencing thus allowed us to detect seven potential somatic insertions with low read counts from two iPSC clones. Negative PCR amplification in parental cells,presence of a polyA tail and absence from seven L1 germline insertion databases highly suggested true somatic insertions in iPSCs. Furthermore,these insertions could not be detected in iPSCs by PCR,likely due to low abundance. We conclude that L1Hs retrotransposes at low levels in iPSCs and therefore warrants careful analyses for genotoxic effects. View Publication

The liver is the main organ responsible for the modification,clearance,and transformational toxicity of most xenobiotics owing to its abundance in cytochrome P450 (CYP450) enzymes. However,the scarcity and variability of primary hepatocytes currently limits their utility. Human pluripotent stem cells (hPSCs) represent an excellent source of differentiated hepatocytes; however,current protocols still produce fetal-like hepatocytes with limited mature function. Interestingly,fetal hepatocytes acquire mature CYP450 expression only postpartum,suggesting that nutritional cues may drive hepatic maturation. We show that vitamin K2 and lithocholic acid,a by-product of intestinal flora,activate pregnane X receptor (PXR) and subsequent CYP3A4 and CYP2C9 expression in hPSC-derived and isolated fetal hepatocytes. Differentiated cells produce albumin and apolipoprotein B100 at levels equivalent to primary human hepatocytes,while demonstrating an 8-fold induction of CYP450 activity in response to aryl hydrocarbon receptor (AhR) agonist omeprazole and a 10-fold induction in response to PXR agonist rifampicin. Flow cytometry showed that over 83% of cells were albumin and hepatocyte nuclear factor 4 alpha (HNF4α) positive,permitting high-content screening in a 96-well plate format. Analysis of 12 compounds showed an R(2) correlation of 0.94 between TC50 values obtained in stem cell-derived hepatocytes and primary cells,compared to 0.62 for HepG2 cells. Finally,stem cell-derived hepatocytes demonstrate all toxicological endpoints examined,including steatosis,apoptosis,and cholestasis,when exposed to nine known hepatotoxins. CONCLUSION: Our work provides fresh insights into liver development,suggesting that microbial-derived cues may drive the maturation of CYP450 enzymes postpartum. Addition of these cues results in the first functional,inducible,hPSC-derived hepatocyte for predictive toxicology. (Hepatology 2015). View Publication

Many acute and chronic anaemias,including haemolysis,sepsis and genetic bone marrow failure diseases such as Diamond-Blackfan anaemia,are not treatable with erythropoietin (Epo),because the colony-forming unit erythroid progenitors (CFU-Es) that respond to Epo are either too few in number or are not sensitive enough to Epo to maintain sufficient red blood cell production. Treatment of these anaemias requires a drug that acts at an earlier stage of red cell formation and enhances the formation of Epo-sensitive CFU-E progenitors. Recently,we showed that glucocorticoids specifically stimulate self-renewal of an early erythroid progenitor,burst-forming unit erythroid (BFU-E),and increase the production of terminally differentiated erythroid cells. Here we show that activation of the peroxisome proliferator-activated receptor α (PPAR-α) by the PPAR-α agonists GW7647 and fenofibrate synergizes with the glucocorticoid receptor (GR) to promote BFU-E self-renewal. Over time these agonists greatly increase production of mature red blood cells in cultures of both mouse fetal liver BFU-Es and mobilized human adult CD34(+) peripheral blood progenitors,with a new and effective culture system being used for the human cells that generates normal enucleated reticulocytes. Although Ppara(-/-) mice show no haematological difference from wild-type mice in both normal and phenylhydrazine (PHZ)-induced stress erythropoiesis,PPAR-α agonists facilitate recovery of wild-type but not Ppara(-/-) mice from PHZ-induced acute haemolytic anaemia. We also show that PPAR-α alleviates anaemia in a mouse model of chronic anaemia. Finally,both in control and corticosteroid-treated BFU-E cells,PPAR-α co-occupies many chromatin sites with GR; when activated by PPAR-α agonists,additional PPAR-α is recruited to GR-adjacent sites and presumably facilitates GR-dependent BFU-E self-renewal. Our discovery of the role of PPAR-α agonists in stimulating self-renewal of early erythroid progenitor cells suggests that the clinically tested PPAR-α agonists we used may improve the efficacy of corticosteroids in treating Epo-resistant anaemias. View Publication

PURPOSE: Genz-644282 [8,9-dimethoxy-5-(2-N-methylaminoethyl)-2,3-methylenedioxy-5H-dibenzo[c,h][1,6]naphthyridin-6-one] has emerged as a promising candidate for antitumor agents. This report describes the bone marrow colony-forming unit,granulocyte macrophage (CFU-GM) and tumor cell CFU activity of topoisomerase I (Top1) inhibitors,such as Genz-644282,topotecan,irinotecan/SN-38,and ARC-111,and examines their activity in several human tumor xenograft models. EXPERIMENTAL DESIGN: Colony-forming assays were conducted with mouse and human bone marrow and eight human tumor cell lines. In addition,29 human tumor cell lines representing a range of histology and potential resistance mechanisms were assayed for sensitivity to Genz-644282 in a 72-hour exposure assay. The efficacy of Genz-644282 was compared with standard anticancer drugs (i.e.,irinotecan,docetaxel,and dacarbazine) in human tumor xenografts of colon cancer,renal cell carcinoma,non-small cell lung cancer,and melanoma. RESULTS: Human bone marrow CFU-GM was more sensitive to the Top1 inhibitors than was mouse bone marrow CFU-GM. The ratio of mouse to human IC(90) values was more than 10 for the camptothecins and less than 10 for Genz-644282,which had more potency as a cytotoxic agent toward human tumor cells in culture than the camptothecins in the colony-forming and 72-hour proliferation assays. Genz-644282 has superior or equal antitumor activity in the human tumor xenografts than the standard drug comparators. CONCLUSIONS: On the basis of preclinical activity and safety,Genz-644282 was selected for development and is currently undergoing phase 1 clinical trial. View Publication

SPARC is an extracellular matrix protein that exerts pleiotropic effects on extracellular matrix organization,growth factor availability,cell adhesion,differentiation,and immunity in cancer. Chronic myelogenous leukemia (CML) cells resistant to the BCR-ABL inhibitor imatinib (IM-R cells) were found to overexpress SPARC mRNA. In this study,we show that imatinib triggers SPARC accumulation in a variety of tyrosine kinase inhibitor (TKI)-resistant CML cell lines. SPARC silencing in IM-R cells restored imatinib sensitivity,whereas enforced SPARC expression in imatinib-sensitive cells promoted viability as well as protection against imatinib-mediated apoptosis. Notably,we found that the protective effect of SPARC required intracellular retention inside cells. Accordingly,SPARC was not secreted into the culture medium of IM-R cells. Increased SPARC expression was intimately linked to persistent activation of the Fyn/ERK kinase signaling axis. Pharmacologic inhibition of this pathway or siRNA-mediated knockdown of Fyn kinase resensitized IM-R cells to imatinib. In support of our findings,increased levels of SPARC mRNA were documented in blood cells from CML patients after 1 year of imatinib therapy compared with initial diagnosis. Taken together,our results highlight an important role for the Fyn/ERK signaling pathway in imatinib-resistant cells that is driven by accumulation of intracellular SPARC. View Publication

Even though myelodysplastic syndromes (MDS) are characterized by ineffective hematopoiesis,the molecular alterations that lead to marrow failure have not been well elucidated. We have previously shown that the myelosuppressive TGF-β pathway is constitutively activated in MDS progenitors. Because there is conflicting data about upregulation of extracellular TGF-β levels in MDS,we wanted to determine the molecular basis of TGF-β pathway overactivation and consequent hematopoietic suppression in this disease. We observed that SMAD7,a negative regulator of TGF-β receptor I (TBRI) kinase,is markedly decreased in a large meta-analysis of gene expression studies from MDS marrow-derived CD34(+) cells. SMAD7 protein was also found to be significantly decreased in MDS marrow progenitors when examined immunohistochemically in a bone marrow tissue microarray. Reduced expression of SMAD7 in hematopoietic cells led to increased TGF-β-mediated gene transcription and enhanced sensitivity to TGF-β-mediated suppressive effects. The increased TGF-β signaling due to SMAD7 reduction could be effectively inhibited by a novel clinically relevant TBRI (ALK5 kinase) inhibitor,LY-2157299. LY-2157299 could inhibit TGF-β-mediated SMAD2 activation and hematopoietic suppression in primary hematopoietic stem cells. Furthermore,in vivo administration of LY-2157299 ameliorated anemia in a TGF-β overexpressing transgenic mouse model of bone marrow failure. Most importantly,treatment with LY-2157199 stimulated hematopoiesis from primary MDS bone marrow specimens. These studies demonstrate that reduction in SMAD7 is a novel molecular alteration in MDS that leads to ineffective hematopoiesis by activating of TGF-β signaling in hematopoietic cells. These studies also illustrate the therapeutic potential of TBRI inhibitors in MDS. View Publication

View Publication

Chemotherapy is the most common way to treat malignancies,but myelosuppression,one of its common side-effects,is a formidable problem. The present study described the protective role of dammarane sapogenins (DS),an active fraction from oriental ginseng,on myelosuppression induced by cyclophosphamide (CP) in mice. DS was orally administered at different dosages (37.5,75,and 150 mg/kg) for 10 d after CP administration (200 mg/kg intraperitoneally). The results showed that DS increased the number of white blood cells (WBC) on day 3 and day 7 (P textless 0.05),such that WBC levels were increased by 105.7 ± 29.5% at 75 mg/kg of DS on day 3 (P textless 0.05,compared with the CP group). Similar results were observed in red blood cells and platelets in DS-treated groups. The colony-forming assay demonstrated that the depressed numbers of CFU-GM (colony-forming unit-granulocyte and macrophage),CFU-E (colony-forming unit-erythroid),BFU-E (burst-forming unit-erythroid),CFU-Meg (colony-forming unit-megakaryocyte) and CFU-GEMM (colony-forming unit-granulocyte,-erythrocyte,-monocyte and -megakaryocyte) induced by CP were significantly reversed after DS treatment. Moreover,the ameliorative effect of DS on myelosuppression was also observed in the femur by hematoxylin/eosin staining. In DS-treated groups,ConA-induced splenocyte proliferation was enhanced significantly at all the doses (37.5,75,150 mg/kg) on day 3 at the rate of 50.3 ± 8.0%,77.6 ± 8.5% and 44.5 ± 8.4%,respectively,while lipopolysaccharide-induced proliferation was increased mainly on day 7 (P textless 0.01),with an increased rate of 39.8 ± 5.6%,34.9 ± 6.6% and 38.3 ± 7.3%,respectively. The thymus index was also markedly increased by 70.4% and 36.6% at 75 mg/kg on days 3 and 7,respectively,as compared with the CP group. In summary,DS has a protective function against CP-induced myelosuppression. Its mechanism might be related to stimulating hematopoiesis recovery,as well as enhancing the immunological function. View Publication