大鼠肝卵圆细胞增殖过程中基质细胞衍生因子-1及其受体CXCR4的表达

近年来,有研究表明基质细胞衍生因子1(stromal cell-derived factor-1,SDF-1)和其受体CXCR4(SDF-1/CXCR4)轴在干细胞的增殖分化中起至关重要的作用[1].本研究采用2-乙酰氨基芴联合部分肝脏切除术(AAF/PH)成功诱导肝卵圆细胞增殖,同时给AAF/PH模型大鼠注射CXCR4特异性抑制剂AMD3100,通过检测SDF 1和其受体CXCR4在卵圆细胞增殖过程中表达的变化情况,进一步研究SDF-1/CXCR4轴在肝卵圆细胞增殖过程中的作用.     

Human immunodeficiency virus can infect CD4-negative human fibroblastoid cells.

Certain human immunodeficiency virus (HIV) strains were shown to infect human fibroblastoid cells. Replication was demonstrated only by coculturing normal peripheral blood mononuclear cells or human T-lymphotropic virus type 1-transformed T-cell lines with the infected human cells. This infection of human fibroblastoid cells did not involve the CD4 molecule and did not have the properties of endocytosis. Human sera could be distinguished by their ability to neutralize HIV infection of the fibroblastoid versus human T-cell lines. These observations demonstrate further that other mechanisms for viral entry, besides CD4 binding, must be considered for HIV. They also indicate the wide cellular host range and heterogeneity of HIV strains. The possibility that fibroblastoid cells serve as a reservoir for the AIDS virus and are involved in connective tissue disorders of infected individuals merits attention.     

Differential CD4(+) and CD8(+) T-cell responsiveness in hepatitis C virus infection

This study was performed to compare the vigor and phenotype of virus-specific CD4(+) and CD8(+) T-cell responses in patients with different virologic and clinical outcomes after hepatitis C virus (HCV) infection. The results show that a vigorous and multispecific CD4(+) proliferative T-cell response is maintained indefinitely after recovery from HCV infection whereas it is weak and focused in persistently infected patients. In contrast, the HCV-specific CD8(+) T-cell response was quantitatively low in both groups despite the use of sensitive direct ex vivo intracellular interferon gamma (IFN-gamma) staining. Furthermore, although HCV-specific cytolytic CD8(+) memory T cells were undetectable ex vivo, they were readily expanded from the peripheral blood of chronically HCV-infected patients but not from recovered subjects after in vitro stimulation, suggesting that ongoing viremia is required to maintain the HCV-specific memory CD8(+) T-cell response. HCV-specific CD8(+) T cells displayed a type 1 cytokine profile characterized by production of IFN-gamma despite persistent HCV viremia. The paradoxical observation that HCV-specific CD4(+) T cells survive and CD8(+) T cells are lost after viral clearance while the opposite occurs when HCV persists suggests the existence of differential requirements for the maintenance of CD4(+) and CD8(+) T-cell memory during HCV infection. Furthermore, the relative rarity of circulating CD8(+) effector T cells in chronically infected patients may explain the chronic insidious nature of the liver inflammation and also why they fail to eliminate the virus.     

CD4 and its role in infection of rabbit cell lines by human immunodeficiency virus type 1.

Human CD4 (HuCD4) is the principal receptor for human immunodeficiency virus type 1 (HIV-1) in human cell infection. Susceptibility of rabbit cell lines to infection with HIV-1 raised questions concerning whether a CD4 homolog serves as HIV-1 receptor on rabbit cells. Sequence comparisons of rabbit CD4 (RbCD4) cloned from a rabbit thymus cDNA library showed that 6 of the 18 residues implicated in HIV-1 binding by CD4 differ between the human and rabbit proteins. No correlation between RbCD4 expression by rabbit cell lines and their ability to support HIV-1 infection was seen. Transfection of RbCD4-negative, HTLV-I-transformed cell lines with HuCD4 significantly enhanced HIV-1 infectivity, suggesting that these lines lack a receptor present on other RbCD4-negative lines that produce high levels of p24 in their native state. Inhibition of HIV-1 infection with soluble HuCD4 was demonstrated for all rabbit lines tested, but complete inhibition was obtained only with a rabbit T-cell line expressing RbCD4 and with HuCD4 transfectants. The results suggest that HIV-1 infection of the RbCD4-positive line proceeds through a receptor similar to HuCD4 but that an additional receptor or receptors may serve this purpose in RbCD4-negative lines.     

Correlation between circulating stromal cell-derived factor 1 levels and CD4+ cell count in human immunodeficiency virus type 1-infected individuals.

Stromal cell-derived factor 1 (SDF-1) is the natural ligand that recognizes CXCR4, which also serves as a coreceptor for some strains of HIV-1. In this study, we explored SDF-1 blood levels among HIV-1-infected individuals exhibiting a wide range of CD4+ cell counts. Plasma or serum concentrations of SDF-1 protein were measured by ELISA in samples from 31 HIV-1-seronegative individuals and 79 HIV-1-infected subjects. Although SDF-1 protein levels were stable for months among seronegative individuals (mean intrasubject variation, 17%), the absolute values varied widely (0.28 to 106.5 ng/ml; mean, 25.6 ng/ml). In HIV-1-infected subjects, there was a direct correlation between SDF-1 level and CD4+ cell count. Subjects with fewer than 50 CD4+ cells per cubic microliter of blood had significantly lower mean SDF-1 levels (+/-SD) than did either HIV-1-infected subjects with higher CD4+ cell counts or uninfected controls: CD4+ cell count <50, mean SDF-1 level of 10.7+/-33.7, 50 < CD4+ cell count <200, mean SDF-1 level of 12.9+/-19.0, 200 < CD4+ cell count <500, mean SDF-1 level of 19.3+/-36.8; CD4+ cell count >500, mean SDF-1 level of 18.5+/-25.2; uninfected control mean SDF-1 level, 25.6+/-34.7. No significant change in SDF-1 level was detected after administration of antiretroviral therapy in nine subjects with advanced disease (mean intrasubject variation, 43%). Analysis of SDF-1 mRNA expression in lymph nodes from HIV-1-infected subjects at different disease stages revealed that the medullary cords contained stromal cells that express SDF-1 mRNA. This preliminary analysis suggests a possible link between lower SDF-1 levels and disease progression.     

Human immunodeficiency virus infection of human bone marrow stromal fibroblasts.

The human immunodeficiency virus (HIV) preferentially infects CD4 positive T cells and monocytes. Other human cell types have been reported to be infectable with HIV, including cells of mesenchymal origin. In this report, we show that both primary human bone marrow stromal fibroblasts and an immortalized human stromal fibroblast line are susceptible to HIV infection. These cells are capable of passing HIV to cells of lymphoid or myeloid lineage, and may thereby act as a reservoir of virus. This in vitro system may be a useful model for assessing the pathophysiology of hematopoietic dysfunction in AIDS patients.     

Transforming growth factor-{beta}1 modulates responses of CD34+ cord blood cells to stromal cell-derived factor-1/CXCL12

Disruption of stromal cell-derived factor-1 (SDF-1/CXCL12 [CXC chemokine ligand 12]) interaction leads to mobilization of stem/progenitor cells from bone marrow to circulation. However, prolonged exposure of CD34+ cells to SDF-1 desensitizes them to SDF-1. So how do cells remain responsive to SDF-1 in vivo when they are continuously exposed to SDF-1? We hypothesized that one or more mechanisms mediated by cytokines exist that could modulate SDF-1 responsiveness of CD34+ cells and the desensitization process. We considered transforming growth factor-beta1 (TGF-beta1) a possible candidate, since TGF-beta1 has effects on CD34+ cells and is produced by stromal cells, which provide niches for maintenance and proliferation of stem/progenitor cells. TGF-beta1 significantly restored SDF-1-induced chemotaxis and sustained adhesion responses in cord blood CD34+ cells preexposed to SDF-1. Effects of TGF-beta1 were dependent on the dose and duration of TGF-beta1 pretreatment. Phosphorylation of extracellular signal-regulated kinase 1 (Erk1)/Erk2 was implicated in TGF-beta1 modulation of migratory and adhesion responses to SDF-1. Our results indicate that low levels of TGF-beta1 can modulate SDF-1 responsiveness of CD34+ cells and thus may facilitate SDF-1-mediated retention and nurturing of stem/progenitor cells in bone marrow.     

Stromal cell-derived factor 1/CXCR4 signaling is critical for early human T-cell development.

The present study investigated the potential role of stromal cell-derived factor 1 (SDF-1) in human intrathymic T-cell differentiation. Results show that SDF-1 is produced by human thymic epithelial cells from the subcapsular and medullary areas, and its receptor, CXCR4, is up-regulated on CD34(+) precursor cells committed to the T-cell lineage. Chimeric human-mouse fetal thymus organ culture (FTOC) seeded with purified CD34(+) thymic progenitors and treated with neutralizing antibodies against SDF-1 or CXCR4 showed a significant reduction of the number of human thymocytes and an arrested thymocyte differentiation in the transition between CD34(+) precursor cells and CD4(+) immature thymocytes. SDF-1-treated FTOC showed an increase of human thymocyte numbers, mainly affecting the most immature subpopulations. Moreover, these results suggest that CXCR4/SDF-1 signaling is not critical for the CD34(+) cell precursor recruitment to the thymus. On the other hand, SDF-1 significantly increased the viability of CD34(+) T-cell precursors modulating the expression of BCL-2 and BAX genes, and stimulated the proliferation of CD34(+) thymic precursor cells, particularly in synergy with interleukin 7 (IL-7), but not with other cytokines, such as stem cell factor or flt3-ligand. Accordingly, only IL-7 was able to up-regulate CXCR4 expression on CD34(+) thymic progenitors. In addition, deprivation of SDF-1 partially inhibited human thymocyte expansion induced by IL-7 in human-mouse FTOC. This study indicates that SDF-1/CXCR4 signaling is required for the survival, expansion, and subsequent differentiation of human early thymocytes and identifies a new mechanism by which IL-7 mediates its effects on human thymopoiesis.     

胰腺癌及胰腺星状细胞中基质细胞衍生因子SDF-1及其受体CXCR4的表达

目的 检测基质细胞衍生因子(SDF-1)及其受体CXCR4在胰腺癌组织、细胞株及星状细胞(PSC)中的表达.方法 采用免疫组织化学方法 检测37例胰腺癌及10例癌旁正常胰腺组织SDF-1、CXCR4、α-SMA蛋白表达以及细胞株AsPC-1、PSC的SDF-1、CXCR4蛋白表达.RT-PCR检测AsPC-1、BxPC3、SW1990及PSC的SDF-1、CXCR4 mRNA表达.结果 37例胰腺癌CXCR4表达(+)8例、(++)20例、(+++)9例;10例癌旁正常胰腺组织CXCR4表达(-)2例、(+)7例、(++)1例,两者差异显著(P<0.01).胰腺癌的间质组织SDF-1的表达高于癌旁间质组织(P<0.01),并随α-SMA表达的增加而增加.胰腺癌细胞株AsPC-1有CXCR4蛋白表达,而PSC有SDF-1蛋白表达.AsPC-1、BxPC3、SW1990细胞株均有CXCR4 mRNA的表达,而无SDF-1 mRNA的表达;PSC有SDF-1 mRNA表达,CXCR4 mRNA微弱表达.结论 胰腺癌组织及细胞系表达CXCR4,PSC表达SDF-1,PSC有可能通过SDF-1/CXCR4轴促进胰腺癌的侵袭转移.     

Human immunodeficiency virus infection of human brain capillary endothelial cells occurs via a CD4/galactosylceramide-independent mechanism.

Neuropathologic studies of AIDS patients have shown that brain capillary endothelial cells are a cellular target for human immunodeficiency virus (HIV) in vivo. We have established in vitro cultures of primary human brain capillary endothelial (HBCE) cells. Using this model system, we have shown a significant HIV infection of HBCE cells that is productive yet noncytopathic. The infection is mediated by a cellular interaction with gp120 that does not involve CD4 or galactosylceramide. HIV infection of HBCE cells may contribute to AIDS-associated neuropathology by disturbing the physiology of the endothelium and directly or indirectly facilitating dissemination of virus to the central nervous system.     

Human erythrocytes bearing electroinserted CD4 neutralize infection in vitro by primary isolates of human immunodeficiency virus type 1

Human erythrocytes bearing electroinserted full-length CD4 (RBC-CD4) can bind and fuse with a laboratory strain of human immunodeficiency virus type 1 (HIV-1) or with T cells infected by HIV-1. Here we show that RBC-CD4 neutralize primary HIV-1 strains in an assay of cocultivation of peripheral blood mononuclear cells (PBMC) from HIV-1- infected persons with uninfected PBMC. RBC-CD4 inhibited viral p24 core antigen accumulation in these cocultures up to 10,000-fold compared with RBC alone. Viral p24 accumulation was inhibited equally well when measured in culture supernatants or in call extracts. The inhibition was dose-dependent and long-lived. Two types of recombinant CD4 tested in parallel were largely ineffective. The neutralization of primary HIV- 1 by RBC-CD4 in vitro was demonstrated in PBMC cultures from 21 of a total of 23 patients tested at two independent sites. RBC-CD4 may offer a route to blocking HIV-1 infection in vivo.     

Interleukin-7 and infection itself by human immunodeficiency virus 1 favor virus persistence in mature CD4(+)CD8(-)CD3(+) thymocytes through sustained induction of Bcl-2

The sequence of events and the mechanisms leading to the destruction of the thymus during human immunodeficiency virus (HIV) infection are still poorly characterized. Investigated here are the survival capacity on HIV-1 infection of the mature single-positive CD4(+)CD8(-)CD3(+) (SP CD4(+)) and the intermediate CD4(+) CD8(-)CD3(-) thymocytes previously shown to be able to replicate the virus in the thymic microenvironment. It is demonstrated that the mature SP CD4(+) thymocytes exhibit a high survival capacity despite the production of a high yield of viruses. Interleukin-7, reported to be a crucial cofactor of tumor necrosis factor (TNF) to promote HIV replication, is shown here to counteract the apoptotic activity of TNF. Resistance to apoptosis of SP CD4(+) cells is conferred by a high expression of the IL-7 receptor (IL-7R) associated with the capacity of IL-7 to permanently up-regulate Bcl-2. In addition, this high Bcl-2 level is further enhanced by infection itself. In contrast, intermediate thymocytes, which replicate the virus at a lower level, are more sensitive to apoptosis, and their differentiation into double-positive CD4(+)CD8(+)CD3(-) (DP CD3(-)) cells strongly increases their death rate on infection. This sensitivity is related to a lower expression of IL-7R and Bcl-2 in intermediate thymocytes, which further decreases at the DP CD3(-) stage. In addition, a decreased level of Bcl-2 is observed in this subset during infection. Altogether these data suggest that in vivo, HIV infection might create a persistent virus reservoir within the SP CD4(+) thymocytes, whereas the later infection of intermediate cells might lead to thymopoiesis failure.     

Human CD34(+) stem cells express the hiwi gene, a human homologue of the Drosophila gene piwi

Hematopoietic stem cells (HSCs) are characterized by their dual abilities to undergo differentiation into multiple hematopoietic cell lineages or to undergo self-renewal. The molecular basis of these properties remains poorly understood. Recently the piwi gene was found in the embryonic germline stem cells (GSCs) of Drosophila melanogaster and has been shown to be important in GSC self-renewal. This study demonstrated that hiwi, a novel human homologue of piwi, is also present in human CD34(+) hematopoietic progenitor cells but not in more differentiated cell populations. Placing CD34(+) cells into culture conditions that supported differentiation and rapid exit from the stem cell compartment resulted in a loss of hiwi expression by day 5 of a 14-day culture period. Expression of the hiwi gene was detected in many developing fetal and adult tissues. By means of 5' RACE cloning methodology, a novel putative full-length hiwi complementary DNA was cloned from human CD34(+) marrow cells. At the amino acid level, the human HIWI protein was 52% homologous to the Drosophila protein. The transient expression of hiwi in the human leukemia cell line KG1 resulted in a dramatic reduction in cellular proliferation. Overexpression of hiwi led to programmed cell death of KG1 cells as demonstrated by the Annexin V assay system. These studies suggest that hiwi maybe an important negative developmental regulator, which, in part, underlies the unique biologic properties associated with hematopoietic stem and progenitor cells.     

基质细胞衍生因子-1和受体CXCR4在急性白血病和恶性淋巴瘤中的表达

目的分析急性白血病(AL)和恶性淋巴瘤(ML)患者外周血血清基质细胞衍生因子1(SDF1)及其骨髓单个核细胞(MNC)表面特异性受体CXCR4的表达,并进行对照研究。方法ELISA法检测血清中SDF1表达,流式细胞术检测骨髓MNC表面CXCR4的表达。结果26例AL患者包含9例急性淋巴细胞白血病和17例急性非淋巴细胞白血病,其SDF1、CXCR4表达分别为(7115.8±946.5)ng/L、(77.2±9.7)%和(4642.2±1146.8)ng/L、(38.9±11.0)%;18例ML患者包含5例霍奇金淋巴瘤和13例非霍奇金淋巴瘤,其SDF1、CXCR4表达分别为(3728.9±690.9)ng/L、(9.2±2.7)%和(4442.1±1073.0)ng/L、(8.5±2.4)%,上述各组SDF1/CXCR4表达均高于对照组水平(2369.3±966.5)ng/L、(2.7±1.5)%(P<0.01)。有髓外浸润的AL患者其SDF1/CXCR4的表达水平高于同组其他患者,有广泛浸润的ML患者其SDF1的表达水平高于同组其他患者。结论CXCR4/SDF1的高表达与AL和ML的发病及其浸润特性存在一定联系,为上述肿瘤的治疗提供了新思路。