技术资料

Given their self-renewing and pluripotent capabilities,human embryonic stem cells (hESCs) are well poised as a cellular source for tissue regeneration therapy. However,the host immune response against transplanted hESCs is not well characterized. In fact,controversy remains as to whether hESCs have immune-privileged properties. To address this issue,we used in vivo bioluminescent imaging to track the fate of transplanted hESCs stably transduced with a double-fusion reporter gene consisting of firefly luciferase and enhanced GFP. We show that survival after transplant is significantly limited in immunocompetent as opposed to immunodeficient mice. Repeated transplantation of hESCs into immunocompetent hosts results in accelerated hESC death,suggesting an adaptive donor-specific immune response. Our data demonstrate that transplanted hESCs trigger robust cellular and humoral immune responses,resulting in intragraft infiltration of inflammatory cells and subsequent hESC rejection. Moreover,we have found CD4(+) T cells to be an important modulator of hESC immune-mediated rejection. Finally,we show that immunosuppressive drug regimens can mitigate the anti-hESC immune response and that a regimen of combined tacrolimus and sirolimus therapies significantly prolongs survival of hESCs for up to 28 days. Taken together,these data suggest that hESCs are immunogenic,trigger both cellular and humoral-mediated pathways,and,as a result,are rapidly rejected in xenogeneic hosts. This process can be mitigated by a combined immunosuppressive regimen as assessed by molecular imaging approaches. View Publication

Endogenous neural stem/precursor cells (NPCs) are considered a functional reservoir for promoting tissue homeostasis and repair after injury,therefore regenerative strategies that mobilize these cells have recently been proposed. Despite evidence of increased neurogenesis upon acute inflammatory insults (e.g. ischaemic stroke),the plasticity of the endogenous brain stem cell compartment in chronic CNS inflammatory disorders remains poorly characterized. Here we show that persistent brain inflammation,induced by immune cells targeting myelin,extensively alters the proliferative and migratory properties of subventricular zone (SVZ)-resident NPCs in vivo leading to significant accumulation of non-migratory neuroblasts within the SVZ germinal niche. In parallel,we demonstrate a quantitative reduction of the putative brain stem cells proliferation in the SVZ during persistent brain inflammation,which is completely reversed after in vitro culture of the isolated NPCs. Together,these data indicate that the inflamed brain microenvironment sustains a non cell-autonomous dysfunction of the endogenous CNS stem cell compartment and challenge the potential efficacy of proposed therapies aimed at mobilizing endogenous precursors in chronic inflammatory brain disorders. View Publication

TGF-beta can be a potent suppressor of lymphocyte effector cell functions and can mediate these effects via distinct molecular pathways. The role of TGF-beta in regulating CD16-mediated NK cell IFN-gamma production and antibody-dependent cellular cytotoxicity (ADCC) is unclear,as are the signaling pathways that may be utilized. Treatment of primary human NK cells with TGF-beta inhibited IFN-gamma production induced by CD16 activation with or without IL-12 or IL-2,and it did so without affecting the phosphorylation/activation of MAP kinases ERK and p38,as well as STAT4. TGF-beta treatment induced SMAD3 phosphorylation,and ectopic overexpression of SMAD3 resulted in a significant decrease in IFN-gamma gene expression following CD16 activation with or without IL-12 or IL-2. Likewise,NK cells obtained from smad3(-/-) mice produced more IFN-gamma in response to CD16 activation plus IL-12 when compared with NK cells obtained from wild-type mice. Coactivation of human NK cells via CD16 and IL-12 induced expression of T-BET,the positive regulator of IFN-gamma,and T-BET was suppressed by TGF-beta and by SMAD3 overexpression. An extended treatment of primary NK cells with TGF-beta was required to inhibit ADCC,and it did so by inhibiting granzyme A and granzyme B expression. This effect was accentuated in cells overexpressing SMAD3. Collectively,our results indicate that TGF-beta inhibits CD16-mediated human NK cell IFN-gamma production and ADCC,and these effects are mediated via SMAD3. View Publication

Cancer in humans is the result of a multi-step process. This process often involves the activation of oncogenes and/or the inactivation of tumor suppressor genes. These two steps arise not only due to mutations,but can also be the result of a translocation or an altered transcription rate. One important mechanism is the occurrence of epigenetic alterations like promotor methylation (which may lead to tumor suppressor silencing) or decreased histone acetylation (which can result in the downregulation of proteins involved in apoptosis). Today,histone acetylation and DNA methylation are epigenetic modifications which have been linked closely to the pathology of human cancers and inhibitors of both enzyme classes for clinical use are at hand. In contrast,other fields of epigenetics still lack of similarly thorough knowledge. This is especially true for the group of histone methyltransferases and their inhibitors. Since connections between histone methylation patterns and cancer progression have been recognized,histone methyltransferases represent promising targets for future cancer treatment. View Publication

The developmental potential of human ES cells makes them an important tool in developmental,pharmacological,and clinical research. For human ES cell technology to be fully exploited,however,culture efficiency must be improved,large-scale culture enabled,and safety ensured. Traditional human ES cell culture systems have relied on serum products and mouse feeder layers,which limit the scale,present biological variability,and expose the cells to potential contaminants. Defined,feeder-independent culture systems improve the safety and efficiency of ES cell technology,enabling translational research. The protocols herein are designed with the standard research laboratory in mind. They contain recipes for the formulation of mTeSR (a defined medium for human ES cell culture) and detailed protocols for the culture,transfer,and passage of cells grown in these feeder-independent conditions. They provide a basis for routine feeder-independent culture,and a starting point for additional optimization of culture conditions. View Publication

Recent evidence suggests that blockade of aberrant Hedgehog signaling can be exploited as a therapeutic strategy for pancreatic cancer. Our previous studies using the prototype Hedgehog small-molecule antagonist cyclopamine had shown the striking inhibition of systemic metastases on Hedgehog blockade in spontaneously metastatic orthotopic xenograft models. Cyclopamine is a natural compound with suboptimal pharmacokinetics,which impedes clinical translation. In the present study,a novel,orally bioavailable small-molecule Hedgehog inhibitor,IPI-269609,was tested using in vitro and in vivo model systems. In vitro treatment of pancreatic cancer cell lines with IPI-269609 resembled effects observed using cyclopamine (i.e.,Gli-responsive reporter knockdown,down-regulation of the Hedgehog target genes Gli1 and Ptch,as well as abrogation of cell migration and colony formation in soft agar). Single-agent IPI-269609 profoundly inhibited systemic metastases in orthotopic xenografts established from human pancreatic cancer cell lines,although Hedgehog blockade had minimal effect on primary tumor volume. The only discernible phenotype observed within the treated primary tumor was a significant reduction in the population of aldehyde dehydrogenase-bright cells,which we have previously identified as a clonogenic tumor-initiating population in pancreatic cancer. Selective ex vivo depletion of aldehyde dehydrogenase-bright cells with IPI-269609 was accompanied by significant reduction in tumor engraftment rates in athymic mice. Pharmacologic blockade of aberrant Hedgehog signaling might prove to be an effective therapeutic strategy for inhibition of systemic metastases in pancreatic cancer,likely through targeting subsets of cancer cells with tumor-initiating (cancer stem cell") properties." View Publication

With their unique ability to differentiate into all cell types,embryonic stem (ES) cells hold great therapeutic promise. To improve the efficiency of embryoid body (EB)-mediated ES cell differentiation,we studied murine EBs on the basis of their size and found that EBs with an intermediate size (diameter 100-300 microm) are the most proliferative,hold the greatest differentiation potential,and have the lowest rate of cell death. In an attempt to promote the formation of this subpopulation,we surveyed several biocompatible substrates with different surface chemical parameters and identified a strong correlation between hydrophobicity and EB development. Using self-assembled monolayers of various lengths of alkanethiolates on gold substrates,we directly tested this correlation and found that surfaces that exhibit increasing hydrophobicity enrich for the intermediate-size EBs. When this approach was applied to the human ES cell system,similar phenomena were observed. Our data demonstrate that hydrophobic surfaces serve as a platform to deliver uniform EB populations and may significantly improve the efficiency of ES cell differentiation. View Publication

Epithelial-mesenchymal transition (EMT) plays important roles in various physiological and pathological processes,and is regulated by signaling pathways mediated by cytokines,including transforming growth factor beta (TGFbeta). Embryonic endothelial cells also undergo differentiation into mesenchymal cells during heart valve formation and aortic maturation. However,the molecular mechanisms that regulate such endothelial-mesenchymal transition (EndMT) remain to be elucidated. Here we show that TGFbeta plays important roles during mural differentiation of mouse embryonic stem cell-derived endothelial cells (MESECs). TGFbeta2 induced the differentiation of MESECs into mural cells,with a decrease in the expression of the endothelial marker claudin 5,and an increase in expression of the mural markers smooth muscle alpha-actin,SM22alpha and calponin,whereas a TGFbeta type I receptor kinase inhibitor inhibited EndMT. Among the transcription factors involved in EMT,Snail was induced by TGFbeta2 in MESECs. Tetracycline-regulated expression of Snail induced the differentiation of MESECs into mural cells,whereas knockdown of Snail expression abrogated TGFbeta2-induced mural differentiation of MESECs. These results indicate that Snail mediates the actions of endogenous TGFbeta signals that induce EndMT. View Publication

Expression of Mpl is restricted to hematopoietic cells in the megakaryocyte lineage and to undifferentiated progenitors,where it initiates critical cell survival and proliferation signals after stimulation by its ligand,thrombopoietin (TPO). As a result,a deficiency in Mpl function in patients with congenital amegakaryocytic thrombocytopenia (CAMT) and in mpl(-/-) mice produces profound thrombocytopenia and a severe stem cell-repopulating defect. Gene therapy has the potential to correct the hematopoietic defects of CAMT by ectopic gene expression that restores normal Mpl receptor activity. We rescued the mpl(-/-) mouse with a transgenic vector expressing mpl from the promoter elements of the 2-kb region of DNA just proximal to the natural gene start site. Transgene rescued mice exhibit thrombocytosis but only partial correction of the stem cell defect. Furthermore,they show very low-level expression of Mpl on platelets and megakaryocytes,and the transgene-rescued megakaryocytes exhibit diminished TPO-dependent kinase phosphorylation and reduced platelet production in bone marrow chimeras. Thrombocytosis is an unexpected consequence of reduced Mpl expression and activity. However,impaired TPO homeostasis in the transgene-rescued mice produces elevated plasma TPO levels,which serves as an unchecked stimulus to drive the observed excessive megakaryocytopoiesis. View Publication

Decay-accelerating factor (DAF) is a cell surface regulator that accelerates the dissociation of C3/C5 convertases and thereby prevents the amplification of complement activation on self cells. In the context of transplantation,DAF has been thought to primarily regulate antibody-mediated allograft injury,which is in part serum complement-dependent. Based on our previously delineated link between DAF and CD4 T cell responses,we evaluated the effects of donor Daf1 (the murine homolog of human DAF) deficiency on CD8 T cell-mediated cardiac allograft rejection. MHC-disparate Daf1(-/-) allografts were rejected with accelerated kinetics compared with wild-type grafts. The accelerated rejection predominantly tracked with DAF's absence on bone marrow-derived cells in the graft and required allograft production of C3. Transplantation of Daf1(-/-) hearts into wild-type allogeneic hosts augmented the strength of the anti-donor (direct pathway) T cell response,in part through complement-dependent proliferative and pro-survival effects on alloreactive CD8 T cells. The accelerated allograft rejection of Daf1(-/-) hearts occurred in recipients lacking anti-donor Abs. The results reveal that donor DAF expression,by controlling local complement activation on interacting T cell APC partners,regulates the strength of the direct alloreactive CD8(+) T cell response. The findings provide new insights into links between innate and adaptive immunity that could be exploited to limit T cell-mediated injury to an allograft following transplantation. View Publication

Peripheral CD103(+)Foxp3(+) regulatory T cells (Tregs) can develop both from conventional naive T cells upon cognate Ag delivery under tolerogenic conditions and from thymic-derived,expanded/differentiated natural Tregs. We here show that CD47 expression,a marker of self on hematopoietic cells,selectively regulated CD103(+)Foxp3(+) Treg homeostasis at the steady state. First,the proportion of effector/memory-like (CD44(high)CD62L(low)) CD103(+)Foxp3(+) Tregs rapidly augmented with age in CD47-deficient mice (CD47(-/-)) as compared with age-matched control littermates. Yet,the percentage of quiescent (CD44(low)CD62L(high)) CD103(-)Foxp3(+) Tregs remained stable. Second,the increased proliferation rate (BrdU incorporation) observed within the CD47(-/-)Foxp3(+) Treg subpopulation was restricted to those Tregs expressing CD103. Third,CD47(-/-) Tregs maintained a normal suppressive function in vitro and in vivo and their increased proportion in old mice led to a decline of Ag-specific T cell responses. Thus,sustained CD47 expression throughout life is critical to avoid an excessive expansion of CD103(+) Tregs that may overwhelmingly inhibit Ag-specific T cell responses. View Publication

The human transferrin receptor (hTfR) is a target for cancer immunotherapy due to its overexpression on the surface of cancer cells. We previously developed an antibody-avidin fusion protein that targets hTfR (anti-hTfR IgG3-Av) and exhibits intrinsic cytotoxicity against certain malignant cells. Gambogic acid (GA),a drug that also binds hTfR,induces cytotoxicity in several malignant cell lines. We now report that anti-hTfR IgG3-Av and GA induce cytotoxicity in a new broader panel of hematopoietic malignant cell lines. Our results show that the effect of anti-hTfR IgG3-Av is iron-dependent whereas that of GA is iron-independent in all cells tested. In addition,we observed that GA exerts a TfR-independent cytotoxicity. We also found that GA increases the generation of reactive oxygen species that may play a role in the cytotoxicity induced by this drug. Additive cytotoxicity was observed by simultaneous combination treatment with these drugs and synergy by using anti-hTfR IgG3-Av as a chemosensitizing agent. In addition,we found a concentration of GA that is toxic to malignant hematopoietic cells but not to human hematopoietic progenitor cells. Our results suggest that these two compounds may be effective,alone or in combination,for the treatment of human hematopoietic malignancies. View Publication