技术资料

Differences in clinical outcome of simian immunodeficiency virus (SIV) infection in disease-resistant African sooty mangabeys (SM) and disease-susceptible Asian rhesus macaques (RM) prompted us to examine the role of regulatory T cells (Tregs) in these two animal models. Results from a cross-sectional study revealed maintenance of the frequency and absolute number of peripheral Tregs in chronically SIV-infected SM while a significant loss occurred in chronically SIV-infected RM compared to uninfected animals. A longitudinal study of experimentally SIV-infected animals revealed a transient increase in the frequency of Tregs from baseline values following acute infection in RM,but no change in the frequency of Tregs occurred in SM during this period. Further examination revealed a strong correlation between plasma viral load (VL) and the level of Tregs in SIV-infected RM but not SM. A correlation was also noted in SIV-infected RM that control VL spontaneously or in response to antiretroviral chemotherapy. In addition,immunofluorescent cell count assays showed that while Treg-depleted peripheral blood mononuclear cells from RM led to a significant enhancement of CD4+ and CD8+ T-cell responses to select pools of SIV peptides,there was no detectable T-cell response to the same pool of SIV peptides in Treg-depleted cells from SIV-infected SM. Our data collectively suggest that while Tregs do appear to play a role in the control of viremia and the magnitude of the SIV-specific immune response in RM,their role in disease resistance in SM remains unclear. View Publication

Phosphoinositide 3-kinase (PI3K)-dependent signalling regulates a wide variety of cellular functions including proliferation and differentiation. Disruption of class I(A) PI3K isoforms has implicated PI3K-mediated signalling in development of the early embryo and lymphohaemopoietic system. We have used embryonic stem (ES) cells as an in vitro model to study the involvement of PI3K-dependent signalling during early development and haemopoiesis. Both pharmacological inhibition and genetic manipulation of PI3K-dependent signalling demonstrate that PI3K-mediated signals,most likely via 3-phosphoinositide-dependent protein kinase 1 (PDK1),are required for proliferation of cells within developing embryoid bodies (EBs). Surprisingly,the haemopoietic potential of EB-derived cells was not blocked upon PI3K inhibition but rather enhanced,correlating with modest increases in expression of haemopoietic marker genes. By contrast,PDK1-deficient EB-derived progeny failed to generate terminally differentiated haemopoietic lineages. This deficiency appeared to be due to a requirement for PI3K signalling during the proliferative phase of blast-colony-forming cell (BL-CFC) expansion,rather than as a result of effects on differentiation per se. We also demonstrate that PI3K-dependent signalling is required for optimal generation of erythroid and myeloid progenitors and their differentiation into mature haemopoietic colony types. These data demonstrate that PI3K-dependent signals play important roles at different stages of haemopoietic development. View Publication

Ubiquitously acting chromatin opening elements (UCOEs) consist of methylation-free CpG islands encompassing dual divergently transcribed promoters of housekeeping genes that have been shown to confer resistance to transcriptional silencing and to produce consistent and stable transgene expression in tissue culture systems. To develop improved strategies for hematopoietic cell gene therapy,we have assessed the potential of the novel human HNRPA2B1-CBX3 UCOE (A2UCOE) within the context of a self-inactivating (SIN) lentiviral vector. Unlike viral promoters,the enhancer-less A2UCOE gave rise to populations of cells that expressed a reporter transgene at a highly reproducible level. The efficiency of expression per vector genome was also markedly increased in vivo compared with vectors incorporating either spleen focus-forming virus (SFFV) or cytomegalovirus (CMV) promoters,suggesting a relative resistance to silencing. Furthermore,an A2UCOE-IL2RG vector fully restored the IL-2 signaling pathway within IL2RG-deficient human cells in vitro and successfully rescued the X-linked severe combined immunodeficiency (SCID-X1) phenotype in a mouse model of this disease. These data indicate that the A2UCOE displays highly reliable transcriptional activity within a lentiviral vector,largely overcoming insertion-site position effects and giving rise to therapeutically relevant levels of gene expression. These properties are achieved in the absence of classic enhancer activity and therefore may confer a high safety profile. View Publication

The aims of our study were to verify whether it was possible to generate in vitro,from different adult human tissues,a population of cells that behaved,in culture,as multipotent stem cells and if these latter shared common properties. To this purpose,we grew and cloned finite cell lines obtained from adult human liver,heart,and bone marrow and named them human multipotent adult stem cells (hMASCs). Cloned hMASCs,obtained from the 3 different tissues,expressed the pluripotent state-specific transcription factors Oct-4,NANOG,and REX1,displayed telomerase activity,and exhibited a wide range of differentiation potential,as shown both at a morphologic and functional level. hMASCs maintained a human diploid DNA content,and shared a common gene expression signature,compared with several somatic cell lines and irrespectively of the tissue of isolation. In particular,the pathways regulating stem cell self-renewal/maintenance,such as Wnt,Hedgehog,and Notch,were transcriptionally active. Our findings demonstrate that we have optimized an in vitro protocol to generate and expand cells from multiple organs that could be induced to acquire morphologic and functional features of mature cells even embryologically not related to the tissue of origin. View Publication

Homing of hematopoietic stem cells (HSCs) into the bone marrow (BM) is a prerequisite for establishment of hematopoiesis during development and following transplantation. However,the molecular interactions that control homing of HSCs,in particular,of fetal HSCs,are not well understood. Herein,we studied the role of the alpha6 and alpha4 integrin receptors for homing and engraftment of fetal liver (FL) HSCs and hematopoietic progenitor cells (HPCs) to adult BM by using integrin alpha6 gene-deleted mice and function-blocking antibodies. Both integrins were ubiquitously expressed in FL Lin(-)Sca-1(+)Kit(+) (LSK) cells. Deletion of integrin alpha6 receptor or inhibition by a function-blocking antibody inhibited FL LSK cell adhesion to its extracellular ligands,laminins-411 and -511 in vitro,and significantly reduced homing of HPCs to BM. In contrast,the anti-integrin alpha6 antibody did not inhibit BM homing of HSCs. In agreement with this,integrin alpha6 gene-deleted FL HSCs did not display any homing or engraftment defect compared with wild-type littermates. In contrast,inhibition of integrin alpha4 receptor by a function-blocking antibody virtually abrogated homing of both FL HSCs and HPCs to BM,indicating distinct functions for integrin alpha6 and alpha4 receptors during homing of fetal HSCs and HPCs. View Publication

In CD34(+) acute myeloid leukemia (AML),the malignant stem cells reside in the CD38(-) compartment. We have shown before that the frequency of such CD34(+)CD38(-) cells at diagnosis correlates with minimal residual disease (MRD) frequency after chemotherapy and with survival. Specific targeting of CD34(+)CD38(-) cells might thus offer therapeutic options. Previously,we found that C-type lectin-like molecule-1 (CLL-1) has high expression on the whole blast compartment in the majority of AML cases. We now show that CLL-1 expression is also present on the CD34(+)CD38(-) stem- cell compartment in AML (77/89 patients). The CD34(+)CLL-1(+) population,containing the CD34(+)CD38(-)CLL-1(+) cells,does engraft in nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice with outgrowth to CLL-1(+) blasts. CLL-1 expression was not different between diagnosis and relapse (n = 9). In remission,both CLL-1(-) normal and CLL-1(+) malignant CD34(+)CD38(-) cells were present. A high CLL-1(+) fraction was associated with quick relapse. CLL-1 expression is completely absent both on CD34(+)CD38(-) cells in normal (n = 11) and in regenerating bone marrow controls (n = 6). This AML stem-cell specificity of the anti-CLL-1 antibody under all conditions of disease and the leukemia-initiating properties of CD34(+)CLL-1(+) cells indicate that anti-CLL-1 antibody enables both AML-specific stem-cell detection and possibly antigen-targeting in future. View Publication

Mesenchymal stromal cells (MSC) provide a supportive cellular microenvironment and are able to maintain the self-renewal capacity of hematopoietic progenitor cells (HPC). Isolation procedures for MSC vary extensively,and this may influence their biologic properties. In this study,we have compared human MSC isolated from bone marrow (BM) using two culture conditions,from cord blood (CB),and from adipose tissue (AT). The ability to maintain long-term culture-initiating cell frequency and a primitive CD34(+)CD38(-) immunophenotype was significantly higher for MSC derived from BM and CB compared with those from AT. These results were in line with a significantly higher adhesion of HPC to MSC from BM and CB versus MSC from AT. We have compared the cytokine production of MSC by cytokine antibody arrays,enzyme-linked immunosorbent assay,and a cytometric bead array. There were reproducible differences in the chemokine secretion profiles of various MSC preparations,but there was no clear concordance with differences in their potential to maintain primitive function of HPC. Global gene expression profiles of MSC preparations were analyzed and showed that adhesion proteins including cadherin-11,N-cadherin,vascular cell adhesion molecule 1,neural cell adhesion molecule 1,and integrins were highly expressed in MSC preparations derived from BM and CB. Thus,MSC from BM and CB are superior to MSC from AT for maintenance of primitive HPC. The latter property is associated with specific molecular profiles indicating the significance of cell-cell junctions but not with secretory profiles. Disclosure of potential conflicts of interest is found at the end of this article. View Publication

The histo-blood group i and I antigens have been characterized as straight and branched repeats of N-acetyllactosamine,respectively,and the conversion of the straight-chain i to the branched-chain I structure on red cells is regulated to occur after birth. It has been demonstrated that the human I locus expresses 3 IGnT transcripts,IGnTA,IGnTB,and IGnTC,and that the last of these is responsible for the I branching formation on red cells. In the present investigation,the K-562 cell line was used as a model to show that the i-to-I transition in erythroid differentiation is determined by the transcription factor CCAAT/enhancer binding protein alpha (C/EBPalpha),which enhances transcription of the IGnTC gene,consequently leading to formation of the I antigen. Further investigation suggested that C/EBPalpha IGnTC-activation activity is modulated at a posttranslational level,and that the phosphorylation status of C/EBPalpha may have a crucial effect. Results from studies using adult and cord erythropoietic cells agreed with those derived using the K-562 cell model,with lentiviral expression of C/EBPalpha in CD34(+) hemopoietic cells demonstrating the determining role of C/EBPalpha in the induction of the IGnTC gene as well as in I antigen expression. View Publication

Recently,a number of clinical trials used either mesenchymal stem cells (MSCs) or natural killer (NK) cells in an attempt to improve the effectiveness of hematopoietic stem cell transplantation (HSCT). In view of the relevant role of both MSCs and NK cells in HSCT,we have recently explored the result of possible interactions between the 2 cell types. We found that activated NK cells could kill MSCs,whereas MSCs strongly inhibited interleukin-2 (IL-2)-induced NK-cell proliferation. In this study,we further analyzed the inhibitory effect exerted by MSCs on NK cells. We show that MSCs not only inhibit the cytokine-induced proliferation of freshly isolated NK cells but also prevent the induction of effector functions,such as cytotoxic activity and cytokine production. Moreover,we show that this inhibitory effect is related to a sharp down-regulation of the surface expression of the activating NK receptors NKp30,NKp44,and NKG2D. Finally,we demonstrate that indoleamine 2,3-dioxygenase and prostaglandin E2 represent key mediators of the MSC-induced inhibition of NK cells. View Publication

Successful reprogramming of differentiated human somatic cells into a pluripotent state would allow creation of patient- and disease-specific stem cells. We previously reported generation of induced pluripotent stem (iPS) cells,capable of germline transmission,from mouse somatic cells by transduction of four defined transcription factors. Here,we demonstrate the generation of iPS cells from adult human dermal fibroblasts with the same four factors: Oct3/4,Sox2,Klf4,and c-Myc. Human iPS cells were similar to human embryonic stem (ES) cells in morphology,proliferation,surface antigens,gene expression,epigenetic status of pluripotent cell-specific genes,and telomerase activity. Furthermore,these cells could differentiate into cell types of the three germ layers in vitro and in teratomas. These findings demonstrate that iPS cells can be generated from adult human fibroblasts. View Publication