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Showing papers on "Transdifferentiation published in 2011"


Journal ArticleDOI
TL;DR: The role of TGF-β signaling pathways in the fibrotic response is summarized in this minireview, which summarizes the involvement of the canonical activin receptor-like kinase 5/Smad3 pathway in fibrosis.
Abstract: Transforming growth factor β (TGF-β) is a central mediator of fibrogenesis. TGF-β is upregulated and activated in fibrotic diseases and modulates fibroblast phenotype and function, inducing myofibroblast transdifferentiation while promoting matrix preservation. Studies in a wide range of experimental models have demonstrated the involvement of the canonical activin receptor-like kinase 5/Smad3 pathway in fibrosis. Smad-independent pathways may regulate Smad activation and, under certain conditions, may directly transduce fibrogenic signals. The profibrotic actions of TGF-β are mediated, at least in part, through induction of its downstream effector, connective tissue growth factor. In light of its essential role in the pathogenesis of fibrosis, TGF-β has emerged as an attractive therapeutic target. However, the pleiotropic and multifunctional effects of TGF-β and its role in tissue homeostasis, immunity and cell proliferation raise concerns regarding potential side effects that may be caused by TGF-β bloc...

857 citations


Journal ArticleDOI
TL;DR: It is shown that conventional reprogramming towards pluripotency through overexpression of Oct4, Sox2, Klf4 and c-Myc can be shortcut and directed towards cardiogenesis in a fast and efficient manner.
Abstract: Here we show that conventional reprogramming towards pluripotency through overexpression of Oct4, Sox2, Klf4 and c-Myc can be shortcut and directed towards cardiogenesis in a fast and efficient manner. With as little as 4 days of transgenic expression of these factors, mouse embryonic fibroblasts (MEFs) can be directly reprogrammed to spontaneously contracting patches of differentiated cardiomyocytes over a period of 11-12 days. Several lines of evidence suggest that a pluripotent intermediate is not involved. Our method represents a unique strategy that allows a transient, plastic developmental state established early in reprogramming to effectively function as a cellular transdifferentiation platform, the use of which could extend beyond cardiogenesis. Our study has potentially wide-ranging implications for induced pluripotent stem cell (iPSC)-factor-based reprogramming and broadens the existing paradigm.

637 citations


Journal ArticleDOI
30 Jun 2011-Nature
TL;DR: It is demonstrated in mice that the adult heart contains a resident stem or progenitor cell population, which has the potential to contribute bona fide terminally differentiated cardiomyocytes after myocardial infarction and is shown to structurally and functionally integrate with resident muscle.
Abstract: A significant bottleneck in cardiovascular regenerative medicine is the identification of a viable source of stem/progenitor cells that could contribute new muscle after ischaemic heart disease and acute myocardial infarction. A therapeutic ideal--relative to cell transplantation--would be to stimulate a resident source, thus avoiding the caveats of limited graft survival, restricted homing to the site of injury and host immune rejection. Here we demonstrate in mice that the adult heart contains a resident stem or progenitor cell population, which has the potential to contribute bona fide terminally differentiated cardiomyocytes after myocardial infarction. We reveal a novel genetic label of the activated adult progenitors via re-expression of a key embryonic epicardial gene, Wilm's tumour 1 (Wt1), through priming by thymosin β4, a peptide previously shown to restore vascular potential to adult epicardium-derived progenitor cells with injury. Cumulative evidence indicates an epicardial origin of the progenitor population, and embryonic reprogramming results in the mobilization of this population and concomitant differentiation to give rise to de novo cardiomyocytes. Cell transplantation confirmed a progenitor source and chromosome painting of labelled donor cells revealed transdifferentiation to a myocyte fate in the absence of cell fusion. Derived cardiomyocytes are shown here to structurally and functionally integrate with resident muscle; as such, stimulation of this adult progenitor pool represents a significant step towards resident-cell-based therapy in human ischaemic heart disease.

614 citations


Journal ArticleDOI
TL;DR: Current research aims to understand how the processes of dedifferentiation, transdifferentiation or reprogramming work and to eventually harness them for use in regenerative medicine.
Abstract: The ultimate goal of regenerative medicine is to replace lost or damaged cells. This can potentially be accomplished using the processes of dedifferentiation, transdifferentiation or reprogramming. Recent advances have shown that the addition of a group of genes can not only restore pluripotency in a fully differentiated cell state (reprogramming) but can also induce the cell to proliferate (dedifferentiation) or even switch to another cell type (transdifferentiation). Current research aims to understand how these processes work and to eventually harness them for use in regenerative medicine.

607 citations


Journal ArticleDOI
TL;DR: In this paper, transient induction of the four reprogramming factors (Oct4, Sox2, Klf4, and c-Myc) can efficiently transdifferentiate fibroblasts into functional neural stem/progenitor cells (NPCs) with appropriate signaling inputs.
Abstract: The simple yet powerful technique of induced pluripotency may eventually supply a wide range of differentiated cells for cell therapy and drug development. However, making the appropriate cells via induced pluripotent stem cells (iPSCs) requires reprogramming of somatic cells and subsequent redifferentiation. Given how arduous and lengthy this process can be, we sought to determine whether it might be possible to convert somatic cells into lineage-specific stem/progenitor cells of another germ layer in one step, bypassing the intermediate pluripotent stage. Here we show that transient induction of the four reprogramming factors (Oct4, Sox2, Klf4, and c-Myc) can efficiently transdifferentiate fibroblasts into functional neural stem/progenitor cells (NPCs) with appropriate signaling inputs. Compared with induced neurons (or iN cells, which are directly converted from fibroblasts), transdifferentiated NPCs have the distinct advantage of being expandable in vitro and retaining the ability to give rise to multiple neuronal subtypes and glial cells. Our results provide a unique paradigm for iPSC-factor–based reprogramming by demonstrating that it can be readily modified to serve as a general platform for transdifferentiation.

574 citations


Journal ArticleDOI
TL;DR: EndoMT may be an important mechanism in the pathogenesis of pulmonary, cardiac, and kidney fibrosis, and may represent a novel therapeutic target for fibrotic disorders.
Abstract: The accumulation of a large number of myofibroblasts is responsible for exaggerated and uncontrolled production of extracellular matrix during the development and progression of pathological fibrosis. Myofibroblasts in fibrotic tissues are derived from at least three sources: expansion and activation of resident tissue fibroblasts, transition of epithelial cells into mesenchymal cells (epithelial-mesenchymal transition, EMT), and tissue migration of bone marrow–derived circulating fibrocytes. Recently, endothelial to mesenchymal transition (EndoMT), a newly recognized type of cellular transdifferentiation, has emerged as another possible source of tissue myofibroblasts. EndoMT is a complex biological process in which endothelial cells lose their specific markers and acquire a mesenchymal or myofibroblastic phenotype and express mesenchymal cell products such as α smooth muscle actin (α-SMA) and type I collagen. Similar to EMT, EndoMT can be induced by transforming growth factor (TGF-β). Recent studies using cell-lineage analysis have demonstrated that EndoMT may be an important mechanism in the pathogenesis of pulmonary, cardiac, and kidney fibrosis, and may represent a novel therapeutic target for fibrotic disorders.

484 citations


Journal ArticleDOI
TL;DR: It is suggested that the TDEC is an important player in the resistance to anti-VEGF therapy, and hence a potential target for GBM therapy.
Abstract: Glioblastoma (GBM) is the most malignant brain tumor and is highly resistant to intensive combination therapies and anti-VEGF therapies. To assess the resistance mechanism to anti-VEGF therapy, we examined the vessels of GBMs in tumors that were induced by the transduction of p53+/− heterozygous mice with lentiviral vectors containing oncogenes and the marker GFP in the hippocampus of GFAP-Cre recombinase (Cre) mice. We were surprised to observe GFP+ vascular endothelial cells (ECs). Transplantation of mouse GBM cells revealed that the tumor-derived endothelial cells (TDECs) originated from tumor-initiating cells and did not result from cell fusion of ECs and tumor cells. An in vitro differentiation assay suggested that hypoxia is an important factor in the differentiation of tumor cells to ECs and is independent of VEGF. TDEC formation was not only resistant to an anti-VEGF receptor inhibitor in mouse GBMs but it led to an increase in their frequency. A xenograft model of human GBM spheres from clinical specimens and direct clinical samples from patients with GBM also showed the presence of TDECs. We suggest that the TDEC is an important player in the resistance to anti-VEGF therapy, and hence a potential target for GBM therapy.

470 citations


Journal ArticleDOI
10 Jun 2011-Cell
TL;DR: The pluripotent state of embryonic stem cells provides a unique perspective on regulatory programs that govern self-renewal and differentiation and somatic cell reprogramming, and the complex interrelationships between pluripotency and chromatin factors are illustrated.

388 citations


Journal ArticleDOI
TL;DR: Results suggest that stimulation of endogenous cardiogenic progenitor activity is a critical mechanism of cardiac cell therapy, and therapy with c-kit(+) cells but not mesenchymal stem cells improved cardiac function.

383 citations


Journal ArticleDOI
TL;DR: Two main approaches to accomplishing cell-replacement therapy are reviewed: in vitro directed differentiation, which is used to push pluripotent stem cells, including embryonic stem cells or induced pluripOTS, through steps similar to those that occur during embryonic development; and reprogramming, in which a differentiated cell is converted directly into the cell of interest without proceeding through a pluripotency intermediate.
Abstract: Regenerative medicine offers the hope that cells for disease research and therapy might be created from readily available sources. To fulfil this promise, the cells available need to be converted into the desired cell types. We review two main approaches to accomplishing this goal: in vitro directed differentiation, which is used to push pluripotent stem cells, including embryonic stem cells or induced pluripotent stem cells, through steps similar to those that occur during embryonic development; and reprogramming (also known as transdifferentiation), in which a differentiated cell is converted directly into the cell of interest without proceeding through a pluripotent intermediate. We analyse the status of progress made using these strategies and highlight challenges that must be overcome to achieve the goal of cell-replacement therapy.

280 citations


Journal ArticleDOI
01 Jan 2011-Diabetes
TL;DR: Results indicate that fully differentiated pancreatic endocrine cells can be created via stepwise differentiation of hES cells, and these cells may serve as a useful screening tool for the identification of compounds that modulate glucagon secretion as well as those that promote the transdifferentiation of α-cells to β-cells.
Abstract: OBJECTIVE Differentiation of human embryonic stem (hES) cells to fully developed cell types holds great therapeutic promise. Despite significant progress, the conversion of hES cells to stable, fully differentiated endocrine cells that exhibit physiologically regulated hormone secretion has not yet been achieved. Here we describe an efficient differentiation protocol for the in vitro conversion of hES cells to functional glucagon-producing α- cells. RESEARCH DESIGN AND METHODS Using a combination of small molecule screening and empirical testing, we developed a six-stage differentiation protocol for creating functional α-cells. An extensive in vitro and in vivo characterization of the differentiated cells was performed. RESULTS A high rate of synaptophysin expression (>75%) and robust expression of glucagon and the α-cell transcription factor ARX was achieved. After a transient polyhormonal state in which cells coexpress glucagon and insulin, maturation in vitro or in vivo resulted in depletion of insulin and other β-cell markers with concomitant enrichment of α-cell markers. After transplantation, these cells secreted fully processed, biologically active glucagon in response to physiologic stimuli including prolonged fasting and amino acid challenge. Moreover, glucagon release from transplanted cells was sufficient to reduce demand for pancreatic glucagon, resulting in a significant decrease in pancreatic α-cell mass. CONCLUSIONS These results indicate that fully differentiated pancreatic endocrine cells can be created via stepwise differentiation of hES cells. These cells may serve as a useful screening tool for the identification of compounds that modulate glucagon secretion as well as those that promote the transdifferentiation of α-cells to β-cells.

Journal ArticleDOI
TL;DR: Transposon-based clonal analysis is used to identify the lineage classes that make the adult zebrafish caudal fin and shows that, the same as in growth, lineages retain fate restriction when passed through the regeneration blastema.

Journal ArticleDOI
TL;DR: It is demonstrated that Nkx2.2 is part of a large repression complex in pancreatic β cells that includes DNMT3a, Grg3, and HDAC1, and it is shown that the repressor activities of Nk x 2.2 on the methylated Arx promoter in β cells are the primary regulatory events required for maintaining β-cell identity.
Abstract: Regulation of cell differentiation programs requires complex interactions between transcriptional and epigenetic networks. Elucidating the principal molecular events responsible for the establishment and maintenance of cell fate identities will provide important insights into how cell lineages are specified and maintained and will improve our ability to recapitulate cell differentiation events in vitro. In this study, we demonstrate that Nkx2.2 is part of a large repression complex in pancreatic β cells that includes DNMT3a, Grg3, and HDAC1. Mutation of the endogenous Nkx2.2 tinman (TN) domain in mice abolishes the interaction between Nkx2.2 and Grg3 and disrupts β-cell specification. Furthermore, we demonstrate that Nkx2.2 preferentially recruits Grg3 and HDAC1 to the methylated Aristaless homeobox gene (Arx) promoter in β cells. The Nkx2.2 TN mutation results in ectopic expression of Arx in β cells, causing β-to-α-cell transdifferentiation. A corresponding β-cell-specific deletion of DNMT3a is also sufficient to cause Arx-dependent β-to-α-cell reprogramming. Notably, subsequent removal of Arx in the β cells of Nkx2.2(TNmut/TNmut) mutant mice reverts the β-to-α-cell conversion, indicating that the repressor activities of Nkx2.2 on the methylated Arx promoter in β cells are the primary regulatory events required for maintaining β-cell identity.

Journal ArticleDOI
TL;DR: The results suggest that miR-125b is involved in vascular calcification in vitro and in vivo, at least partially by targeting SP7, as revealed by expression analysis revealed the osteoblast transcription factor SP7 (osterix) as a target of miR -125b.
Abstract: Vascular calcification is a prominent feature of atherosclerosis and is closely linked to osteoporosis. Cellular differentiation is regulated by various microRNAs (miRs), including miR-125b, which is known to be involved in osteoblast differentiation. However, no specific miR has been defined that modulates vascular calcification. Herein, we assessed the impact of miR-125b in osteogenic transformation of vascular smooth muscle cells. Osteogenic transdifferentiation of human coronary artery smooth muscle cells was induced by osteogenic medium and enhanced the formation of mineralized matrix, resulting in a significantly higher mineral deposition after 21 days. Increased expression of miR-125b was time-dependent in human coronary artery smooth muscle cells and diminished during osteogenic transdifferentiation. At day 21, miR-125b was significantly reduced (−42%) compared with that in the untreated control. The expression of miR-processing enzymes, RNase III endonucleases DICER1 and DROSHA, was also decreased. Furthermore, inhibition of endogenous miR-125b promoted osteogenic transdifferentiation, as measured by increased alkaline phosphatase activity and matrix mineralization. Expression analysis revealed the osteoblast transcription factor SP7 (osterix) as a target of miR-125b. In vivo, miR-125b was decreased in calcified aortas of apolipoprotein E knockout mice. In conclusion, our results suggest that miR-125b is involved in vascular calcification in vitro and in vivo, at least partially by targeting SP7. Evaluating the role of miRs in arterial calcification in vivo may have important therapeutic implications.

Journal ArticleDOI
TL;DR: This study shows that mature mammals have a natural capacity to initiate vestibular hair cell regeneration and suggests that regional notch activity is a significant inhibitor of direct transdifferentiation of supporting cells into hair cells following damage.
Abstract: The capacity of adult mammals to regenerate sensory hair cells is not well defined. To explore early steps in this process, we examined reactivation of a transiently expressed developmental gene, Atoh1, in adult mouse utricles after neomycin-induced hair cell death in culture. Using an adenoviral reporter for Atoh1 enhancer, we found that Atoh1 transcription is activated in some hair cell progenitors (supporting cells) 3 d after neomycin treatment. By 18 d after neomycin, the number of cells with Atoh1 transcriptional activity increased significantly, but few cells acquired hair cell features (i.e., accumulated ATOH1 or myosin VIIa protein or developed stereocilia). Treatment with DAPT, an inhibitor of γ-secretase, reduced notch pathway activity, enhanced Atoh1 transcriptional activity, and dramatically increased the number of Atoh1-expressing cells with hair cell features, but only in the striolar/juxtastriolar region. Similar effects were seen with TAPI-1, an inhibitor of another enzyme required for notch activity (TACE). Division of supporting cells was rare in any control or DAPT-treated utricles. This study shows that mature mammals have a natural capacity to initiate vestibular hair cell regeneration and suggests that regional notch activity is a significant inhibitor of direct transdifferentiation of supporting cells into hair cells following damage.

Journal ArticleDOI
TL;DR: Identifying the perturbations in signaling pathways, mediators and differentiation programs that are responsible for SSc tissue damage allows their selective targeting, and opens the door for therapies utilizing novel compounds, or drug repurposing by innovative uses of already-approved drugs.

Journal ArticleDOI
TL;DR: This work shows a feed-forward loop where MyoD indirectly down-regulates MyoR via miR-378 during myogenic differentiation in C2C12 cells, and significantly reduces the ability of MyiR to prevent the MyiD-driven transdifferentiation of fibroblasts.

Journal ArticleDOI
TL;DR: The potential of MSCs as candidates for use in therapies to treat neurological disorders and the molecular and cellular mechanisms by which they are understood to act are discussed.

Journal ArticleDOI
TL;DR: The therapeutic properties of using HFSC to treat LSCD in a mouse model while demonstrating a strong translational potential are highlighted and points to the niche as a key factor for determining stem cell differentiation.
Abstract: Limbal stem cell deficiency (LSCD) leads to severe ocular surface abnormalities that can result in the loss of vision. The most successful therapy currently being used is transplantation of limbal epithelial cell sheets cultivated from a limbal biopsy obtained from the patient's healthy, contralateral eye or cadaveric tissue. In this study, we investigated the therapeutic potential of murine vibrissae hair follicle bulge-derived stem cells (HFSCs) as an autologous stem cell (SC) source for ocular surface reconstruction in patients bilaterally affected by LSCD. This study is an expansion of our previously published work showing transdifferentiation of HFSCs into cells of a corneal epithelial phenotype in an in vitro system. In this study, we used a transgenic mouse model, K12(rtTA/rtTA) /tetO-cre/ROSA(mTmG) , which allows for HFSCs to change color, from red to green, once differentiation to corneal epithelial cells occurs and Krt12, the corneal epithelial-specific differentiation marker, is expressed. HFSCs were isolated from transgenic mice, amplified by clonal expansion on a 3T3 feeder layer, and transplanted on a fibrin carrier to the eye of LSCD wild-type mice (n = 31). The HFSC transplant was able to reconstruct the ocular surface in 80% of the transplanted animals; differentiating into cells with a corneal epithelial phenotype, expressing Krt12, and repopulating the corneal SC pool while suppressing vascularization and conjunctival ingrowth. These data highlight the therapeutic properties of using HFSC to treat LSCD in a mouse model while demonstrating a strong translational potential and points to the niche as a key factor for determining stem cell differentiation.

Journal ArticleDOI
TL;DR: It is indicated that LPA accelerates HCC progression by recruiting PTFs and promoting their transdifferentiation into myofibroblasts and the consequent enhanced proliferation, migration, and invasion of HCC cells.

Journal ArticleDOI
TL;DR: The evidence strongly suggests that under these circumstances, hepatocytes or biliary epithelial cells can function as facultative stem cells for each other and replenish the inhibited cellular compartment by a process of transdifferentiation, involving complex signaling pathways.

Journal ArticleDOI
TL;DR: Nongenetic and genetic lineage tracing methods showed that human acinar cells can transdifferentiate into cells that express specific ductal markers, such as cytokeratin 19, hepatocyte nuclear factor 1β, SOX9, CD133, carbonic anhydrase II, and cystic fibrosis transmembrane conductance regulator.

Journal ArticleDOI
TL;DR: Liver fibrogenic cells are a heterogenous population of cells that include α-smooth muscle actin positive myofibroblasts that promote the progression of chronic liver diseases towards cirrhosis by means of their multiple phenotypic responses to injury.
Abstract: Liver fibrogenic cells are a heterogenous population of cells that include α-smooth muscle actin positive myofibroblasts (MFs). MFs promote the progression of chronic liver diseases (CLDs) towards cirrhosis. MFs are highly proliferative and contractile and promote fibrogenesis by means of their multiple phenotypic responses to injury. These include: excess deposition and altered remodelling of extracellular matrix; the synthesis and release of growth factor which sustain and perpetuate fibrogenesis; chronic inflammatory response and neo-angiogenesis. MFs mainly originate from hepatic stellate cells or portal fibroblasts through activation and transdifferentiation. MFs may also potentially differentiate from bone marrow-derived stem cells. It has been suggested that MFs can be derived from hepatocytes or cholangiocytes through a process of epithelial to mesenchymal transition in the liver, however this is controversial. Hepatic MFs may also modulate the immune responses to hepatocellular carcinomas and metastatic cancers through cross talk with hepatic progenitor and tumour cells.

Journal ArticleDOI
TL;DR: Results suggested that miR‐21 participated in TGF‐β1‐induced myofibroblast transdifferentiation in cancer stroma by targeting PDCD4 and targeting programmed cell death 4 gene.
Abstract: Transforming growth factor-β1 (TGF-β1) induces stromal fibroblast-to-myofibroblast transdifferentiation in the tumor-stroma interactive microenvironment via modulation of multiple phenotypic and functional genes, which plays a critical role in tumor progression. Up to now, the involvement of micro-RNAs (miRNAs) and their roles in TGF-β1-induced myofibroblast differentiation in tumor-stroma interaction are unclear. Using quantitative real-time RT-PCR, we demonstrated that the expression of micro-RNA-21 (miR-21) was upregulated in activated fibroblasts after treatment with TGF-β1 or conditioned medium from cancer cells. To determine the potential roles of miR-21 in TGF-β1-mediated gene regulation during myofibroblast conversion, we showed that miR-21 expression was downregulated by miR-21 inhibitor and upregulated by miR-21 mimic. Interestingly, downregulation of miR-21 with the inhibitor effectively inhibited TGF-β1-induced myofibroblast differentiation while upregulation of miR-21 with a mimic significantly promoted myofibroblast differentiation. We further demonstrated that MiR-21 directly targeted and downregulated programmed cell death 4 (PDCD4) gene, which in turn acted as a negative regulator of several phenotypic and functional genes of myofibroblasts. Taken together, these results suggested that miR-21 participated in TGF-β1-induced myofibroblast transdifferentiation in cancer stroma by targeting PDCD4.

Journal ArticleDOI
TL;DR: The results indicate that gastric fundic lineages display remarkable plasticity in both physiological ontogeny and pathophysiological pre-neoplastic metaplasia.

Journal ArticleDOI
TL;DR: The findings are consistent with the notion that the conversion from pre-B cells to macrophages is mostly direct and does not involve overt retrodifferentiation.
Abstract: Earlier work has shown that pre-B cells can be converted into macrophages by the transcription factor CCAAT/enhancer binding protein α at very high frequencies. Using this system, we performed a systematic analysis of whether during transdifferentiation the cells transiently reactivate progenitor-restricted genes or even retrodifferentiate. A transcriptome analysis of transdifferentiating cells showed that most genes are up- or down-regulated continuously, acquiring a macrophage phenotype within 5 d. In addition, we observed the transient reactivation of a subset of immature myeloid markers, as well as low levels of the progenitor markers Kit and FMS-like tyrosine kinase 3 and a few lineage-inappropriate genes. Importantly, however, we were unable to observe the reexpression of cell-surface marker combinations that characterize hematopoietic stem and progenitor cells, including c-Kit and FMS-like tyrosine kinase 3, even when CAAT/enhancer binding protein α was activated in pre-B cells under culture conditions that favor growth of hematopoietic stem and progenitor cells or when the transcription factor was activated in a time-limited fashion. Together, our findings are consistent with the notion that the conversion from pre-B cells to macrophages is mostly direct and does not involve overt retrodifferentiation.

Journal ArticleDOI
TL;DR: The role of viral FLICE-inhibitory protein (vFLIP) is revealed in the initiation of PEL and MCD by specifically expressing vFLIP at different stages of B cell differentiation in vivo by defining immunological functions for vFLip in vivo and revealing what the authors believe to be a novel viral-mediated tumorigenic mechanism involving B cell reprogramming.
Abstract: Kaposi sarcoma herpesvirus (KSHV) is specifically associated with Kaposi sarcoma (KS) and 2 B cell lymphoproliferative diseases, namely primary effusion lymphoma (PEL) and multicentric Castleman disease (MCD). KS, PEL, and MCD are largely incurable and poorly understood diseases most common in HIV-infected individuals. Here, we have revealed the role of viral FLICE-inhibitory protein (vFLIP) in the initiation of PEL and MCD by specifically expressing vFLIP at different stages of B cell differentiation in vivo. Mice showed MCD-like abnormalities and immunological defects including lack of germinal centers (GCs), impaired Ig class switching, and affinity maturation. In addition, they showed increased numbers of cells expressing cytoplasmic IgM-λ, a thus far enigmatic feature of the KSHV-infected cells in MCD. B cell-derived tumors arose at high incidence and displayed Ig gene rearrangement with downregulated expression of B cell-associated antigens, which are features of PEL. Interestingly, these tumors exhibited characteristics of transdifferentiation and acquired expression of histiocytic/dendritic cell markers. These results define immunological functions for vFLIP in vivo and reveal what we believe to be a novel viral-mediated tumorigenic mechanism involving B cell reprogramming. Additionally, the robust recapitulation of KSHV-associated diseases in mice provides a model to test inhibitors of vFLIP as potential anticancer agents.

Journal ArticleDOI
TL;DR: Results indicate that c-Abl and PKCδ are crucial for TGFβ-induced EndoMT and that imatinib mesylate and rottlerin or similar kinase inhibitor molecules may be effective therapeutic agents for SSc and other fibroproliferative vasculopathies in which EndOMT plays a pathogenetic role.
Abstract: Objective The origin of the mesenchymal cells responsible for the intimal fibrosis in Systemic Sclerosis (SSc) has not been fully identified. Here, we investigated whether subendothelial mesenchymal cells may emerge through transdifferentiation of endothelial cells (EC) into myofibroblasts via endothelial-mesenchymal transition (EndoMT) in vitro and the signaling pathways involved in this process.

Journal ArticleDOI
TL;DR: Lung fibroblasts that become senescent after ionizing radiation may contribute to lung cancer progression, and the presence of irradiation-mediated senescent cells strongly enhances the growth of cancer cells in vitro and in immunocompromised mice in vivo.
Abstract: Cellular senescence, being the result of serial subculturing or of exogenous stresses, is considered to be a potent anticancer mechanism. However, it has been proposed that senescent cells may enhance the growth of adjacent malignant epithelial cells. On the other hand, exposure of tumors to repeated low doses of γ-irradiation is a common treatment regime. Nevertheless, γ-irradiation also affects the neighboring stromal cells and the interaction of the latter with cancer cells. Accordingly, in this study, we have exposed confluent cultures of human lung fibroblasts to repeated subcytotoxic doses of 4 Gy of γ-irradiation. We found that a single dose immediately activates a DNA damage response, leading to an intense, but reversible, cell cycle arrest. After a series of doses (total dose approximately 50 Gy) cellular senescence was accelerated, as shown by permanent growth arrest and the upregulation of specific biochemical and morphological senescence-associated markers. This process was found to be p53-dependent. Next, we studied the effect of these prematurely senescent cells on the growth of human malignant lung cell lines (A549 and H1299) and found that the presence of irradiation-mediated senescent cells strongly enhances the growth of these cancer cells in vitro and in immunocompromised (SCID) mice in vivo. This effect seems not to be related to an induction of epithelial-to-mesenchymal transdifferentiation but, to a significant extent, to the increased expression of matrix metalloproteases (MMPs), as a specific MMP inhibitor significantly restrains the growth of cancer in the presence of senescent fibroblasts. These findings indicate that lung fibroblasts that become senescent after ionizing radiation may contribute to lung cancer progression.

Journal ArticleDOI
TL;DR: The observations suggest the functional role of hGSPCs as endothelial progenitors, which have properties that give rise to VECs, and have the ability to form vascular endothelial tubes.
Abstract: Previous studies suggest that tumor cells might be the progenitor for tumor vasculature. Whether vascular tube formation from transdifferentiation of human glioma stem/progenitor cells (hGSPCs) contribute to angiogenesis of gliomas remain largely uncertain. hGSPCs were isolated from thirteen surgical specimens of gliomas and cultured in medium favored for stem cell growth. In vitro transdifferentiation of hGSPCs was performed under hypoxia. Expression of vascular endothelial cells (VECs) markers CD31, CD34, kinase insert domain receptor (KDR), and von Willebrand factor (vWF) were analyzed with real-time quantitative RT-PCR and immunofluorescence techniques. Vasculogenic mimicry of hGSPCs was evaluated in a tumor stem cell xenograft model in vivo. Relationships between content of hGSPCs and expression levels of both VECs markers and proangiogenic factors in large number of clinical specimens were further investigated in glioma tissue microarray. In vitro, hGSPCs can transdifferentiate into VECs under hypoxia, they manifested typical “flagstone” pattern when cultivated in medium containing VEGF for a few days; when cultivated on Matrigel they were capable of forming capillary-like structures. Expression of VECs markers including CD31, CD34, KDR, and vWF were significantly up-regulated after transdifferentiation. Human leukocyte antigen (HLA) positively stained vessels were observed inside the xenograft tumors after intracerebral transplantation of hGSPCs in athymic nude mice, implied part of tumor cells with human origin were involved in formation of tumor vessels. In surgical specimens of human glioma, tumor vascular cells coexpressing the markers of early VECs (CD34) and markers of hGSPCs (ABCG2 and nestin) suggest that these vascular cells may stemmed from hGSPCs. Our observations suggest the functional role of hGSPCs as endothelial progenitors, which have properties that give rise to VECs, and have the ability to form vascular endothelial tubes. However, unspecific markers (ABCG2, nestin) that stain for both endothelial as well as glioma stem cells, were found to be expressed in tumor vasculature of human specimen, and limit further interpretation of this finding.