Scientific Resources

Tumor angiogenesis is essential for malignant growth and metastasis. Bone marrow (BM)-derived endothelial progenitor cells (EPC) contribute to angiogenesis-mediated tumor growth. EPC ablation can reduce tumor growth; however,the lack of a marker that can track EPCs from the BM to tumor neovasculature has impeded progress in understanding the molecular mechanisms underlying EPC biology. Here,we report the use of transgenic mouse and lentiviral models to monitor the BM-derived compartment of the tumor stroma; this approach exploits the selectivity of the transcription factor inhibitor of DNA binding 1 (Id1) for EPCs to track EPCs in the BM,blood,and tumor stroma,as well as mature EPCs. Acute ablation of BM-derived EPCs using Id1-directed delivery of a suicide gene reduced circulating EPCs and yielded significant defects in angiogenesis-mediated tumor growth. Additionally,use of the Id1 proximal promoter to express microRNA-30-based short hairpin RNA inhibited the expression of critical EPC-intrinsic factors,confirming that signaling through vascular endothelial growth factor receptor 2 is required for EPC-mediated tumor biology. By exploiting the selectivity of Id1 gene expression in EPCs,our results establish a strategy to track and target EPCs in vivo,clarifying the significant role that EPCs play in BM-mediated tumor angiogenesis. View Publication

Systemic lupus erythematosus (SLE) is characterized by increased vascular risk due to premature atherosclerosis independent of traditional risk factors. We previously proposed that IFN-α plays a crucial role in premature vascular damage in SLE. IFN-α alters the balance between endothelial cell apoptosis and vascular repair mediated by endothelial progenitor cells (EPCs) and myeloid circulating angiogenic cells (CACs). In this study,we demonstrate that IFN-α promotes an antiangiogenic signature in SLE and control EPCs/CACs,characterized by transcriptional repression of IL-1α and β,IL-1R1,and vascular endothelial growth factor A,and upregulation of IL-1R antagonist and the decoy receptor IL-1R2. IL-1β promotes significant improvement in the functional capacity of lupus EPCs/CACs,therefore abrogating the deleterious effects of IFN-α. The beneficial effects from IL-1 are mediated,at least in part,by increases in EPC/CAC proliferation,by decreases in EPC/CAC apoptosis,and by preventing the skewing of CACs toward nonangiogenic pathways. IFN-α induces STAT2 and 6 phosphorylation in EPCs/CACs,and JAK inhibition abrogates the transcriptional antiangiogenic changes induced by IFN-α in these cells. Immunohistochemistry of renal biopsies from patients with lupus nephritis,but not anti-neutrophil cytoplasmic Ab-positive vasculitis,showed this pathway to be operational in vivo,with increased IL-1R antagonist,downregulation of vascular endothelial growth factor A,and glomerular and blood vessel decreased capillary density,compared with controls. Our study introduces a novel putative pathway by which type I IFNs may interfere with vascular repair in SLE through repression of IL-1-dependent pathways. This could promote atherosclerosis and loss of renal function in this disease. View Publication

UNLABELLED: Atherosclerosis develops in an environment of endothelial injury and inflammation. Circulating endothelial progenitor cells (EPCs) are required for vascular repair and restoration of normal endothelial function. We tested the hypothesis that the nonselective cyclooxygenase (COX) inhibitor aspirin (ASA) exerts an effect on circulating EPCs. METHODS: As part of a larger study evaluating the effect of aspirin dose in primary and secondary prevention,subjects (n=32) were assigned randomly to either 81 mg or 325 mg aspirin daily for two months,and circulating mononuclear cells were enumerated at the beginning of the study and after 2 months using fluorescent antibodies against CD34 and CD133 as well as based on aldehyde dehydrogenase (ALDH) activity. Brachial artery endothelial function via flow-mediated dilation (BAFMD) and light transmittance platelet aggregometry in response to physiologic agonists was also determined. RESULTS: Subjects taking aspirin at the time of study entry had a lower numbers of CD133+/34+ cells compared to those not previously exposed (0.01% vs. 0.05% of MNCs,Ptextless0.03). After 2 months,subjects randomized to 81 vs. 325 mg of ASA had no significant differences in the median numbers of EPCs,although mean numbers trended lower in the high dose group. Patients on chronic ASA therapy continued to have lower numbers of EPCs. Similar effects were observed in CD34 and CD 133 single-positive cells,as well as ALDH(br) cells. BAFMD did not differ nor change significantly over time between aspirin dose groups. All patients had decreased ex vivo platelet aggregation in response to arachidonic acid and ADP stimulation. CONCLUSIONS: Our preliminary studies suggest that aspirin exerts a time-dependent effect on circulating EPCs. Short-term exposure to differing doses of ASA had indeterminate effects on EPCs levels,suggesting that time of ASA exposure may play a more important role than dose. Determining the responsible mechanism(s) and the overall clinical relevance of these findings will require further investigation. View Publication

AIMS: Endothelial progenitor cells (EPC) have been shown to repair pulmonary endothelium,although they can also migrate into the arterial intima and differentiate into smooth muscle-like (mesenchymal) cells contributing to intimal hyperplasia. The molecular mechanisms by which this process proceeds have not been fully elucidated. Here,we study whether genes involved in the endothelial-to-mesenchymal transition (EnMT) may contribute to the mesenchymal phenotype acquisition of EPC and we evaluate whether transforming growth factor β1 (TGFβ1) is involved in this process. METHODS AND RESULTS: Our results show that co-culture of EPC with smooth muscle cells (SMC) increases the expression of the mesenchymal cell markers α-smooth muscle actin,sm22-α,and myocardin,and decreases the expression of the endothelial cell marker CD31. In the same conditions,we also observed a concomitant increase in the gene expression of the EnMT-related transcription factors: slug,snail,zeb1,and endothelin-1. This indicates that mesenchymal phenotype acquisition occurred through an EnMT-like process. Inhibition of TGFβ receptor I (TGFβRI) downregulated snail gene expression,blocked the EnMT,and facilitated the differentiation of EPC to the endothelial cell lineage. Furthermore,TGFβRI inhibition decreased migration of EPC stimulated by SMC without affecting their functionality and adhesion capacity. CONCLUSION: These results indicate that EPC may differentiate into SMC-like cells through an EnMT-like process and that TGFβI plays an important role in the fate of EPC. View Publication

OBJECTIVES: In this study,we hypothesized that an antihuman-CD34 antibody immobilized on the surface of commercially available sirolimus-eluting stents (SES) could enhance re-endothelialization compared with SES alone. BACKGROUND: Previous experience with antihuman-CD34 antibody surface modified Genous stents (GS) (OrbusNeich Medical,Fort Lauderdale,Florida) has shown enhanced stent endothelialization in vivo. METHODS: In the phase 1 study,stents were deployed in 21 pig coronary arteries for single stenting (9 vessels: 3 GS,3 SES,and 3 bare-metal stents) and overlapping stenting with various combinations (12 vessels: 4 GS+GS,4 SES+SES,and 4 GS+SES) and harvested at 14 days for scanning electron and confocal microscopy. In phase 2,immobilized anti-CD34 antibody coating was applied on commercially available SES (SES-anti-CD34,n = 7) and compared with GS (n = 8) and SES (n = 7) and examined at 3 and 14 days by scanning electron/confocal microscopy analysis. RESULTS: In phase 1,single stent implantation showed greatest endothelialization in GS (99%) and in bare-metal stent (99%) compared with SES (55%,p = 0.048). In overlapping stents,endothelialization at the overlapping zone was significantly greater in GS+GS (95 +/- 6%) and GS+SES (79 +/- 5%) compared with the SES+SES (36 +/- 14%) group (p = 0.007). In phase 2,SES-anti-CD34 resulted in increased endothelialization compared with SES alone at 3 days (SES-anti-CD34 36 +/- 26%; SES 7 +/- 3%; and GS 76 +/- 8%; p = 0.01),and 14 days (SES-anti-CD34 82 +/- 8%; SES 53 +/- 20%; and GS 98 +/- 2%; p = 0.009). CONCLUSIONS: Immobilization of anti-CD34 antibody on SES enhances endothelialization and may potentially be an effective therapeutic alternative to improve currently available drug-eluting stents. View Publication

In ischemic congestive heart failure (CHF),anemia is associated with poor prognosis. Whether anemia develops in nonischemic CHF is uncertain. The hematopoietic inhibitors TNF-alpha and nitric oxide (NO) are activated in ischemic CHF. We examined whether mice with ischemic or nonischemic CHF develop anemia and whether TNF-alpha and NO are involved. We studied mice (n = 7-9 per group) with CHF either due to myocardial infarction (MI) or to overexpression of the Ca(2+)-binding protein calsequestrin (CSQ) or to induced cardiac disruption of the sarcoplasmic reticulum Ca(2+)-ATPase 2 gene (SERCA2 KO). Hematopoiesis was analyzed by colony formation of CD34(+) bone marrow cells. Hemoglobin concentration was 14.0 +/- 0.4 g/dl (mean +/- SD) in controls,while it was decreased to 10.1 +/- 0.4,9.7 +/- 0.4,and 9.6 +/- 0.3 g/dl in MI,CSQ,and SERCA2 KO,respectively (P textless 0.05). Colony numbers per 100,000 CD34(+) cells in the three CHF groups were reduced to 33 +/- 3 (MI),34 +/- 3 (CSQ),and 39 +/- 3 (SERCA2 KO) compared with 68 +/- 4 in controls (P textless 0.05). Plasma TNF-alpha nearly doubled in MI,and addition of anti-TNF-alpha antibody normalized colony formation. Inhibition of colony formation was completely abolished with blockade of endothelial NO synthase in CSQ and SERCA2 KO,but not in MI. In conclusion,the mechanism of anemia in CHF depends on the etiology of cardiac disease; whereas TNF-alpha impairs hematopoiesis in CHF following MI,NO inhibits blood cell formation in nonischemic murine CHF. View Publication

Neonatal hyperoxia impairs vascular and alveolar growth in mice and decreases endothelial progenitor cells. To determine the role of bone marrow-derived cells in restoration of neonatal lung structure after injury,we studied a novel bone marrow myeloid progenitor cell population from Tie2-green fluorescent protein (GFP) transgenic mice (bone marrow-derived angiogenic cells; BMDAC). We hypothesized that treatment with BMDAC would restore normal lung structure in infant mice during recovery from neonatal hyperoxia. Neonatal mice (1-day-old) were exposed to 80% oxygen for 10 days. BMDACs (1 x 10(5)),embryonic endothelial progenitor cells,mouse embryonic fibroblasts (control),or saline were then injected into the pulmonary circulation. At 21 days of age,saline-treated mice had enlarged alveoli,reduced septation,and a reduction in vascular density. In contrast,mice treated with BMDAC had complete restoration of lung structure that was indistinguishable from room air controls. BMDAC comprised 12% of distal lung cells localized to pulmonary vessels or alveolar type II (AT2) cells and persist (8.8%) for 8 wk postinjection. Coculture of AT2 cells or lung endothelial cells (luEC) with BMDAC augmented AT2 and luEC cell growth in vitro. We conclude that treatment with BMDAC after neonatal hyperoxia restores lung structure in this model of bronchopulmonary dysplasia. View Publication

BACKGROUND: Many patients with ischemic heart disease have cardiovascular risk factors such as cigarette smoking. We tested the effect of nicotine (a key component of cigarette smoking) on the therapeutic effects of human embryonic stem cell-derived endothelial cells (hESC-ECs).backslashnbackslashnMETHODS AND RESULTS: To induce endothelial cell differentiation,undifferentiated hESCs (H9 line) underwent 4-day floating EB formation and 8-day outgrowth differentiation in EGM-2 media. After 12 days,CD31(+) cells (13.7+/-2.5%) were sorted by FACScan and maintained in EGM-2 media for further differentiation. After isolation,these hESC-ECs expressed endothelial specific markers such as vWF (96.3+/-1.4%),CD31 (97.2+/-2.5%),and VE-cadherin (93.7+/-2.8%),form vascular-like channels,and incorporated DiI-labeled acetylated low-density lipoprotein (DiI-Ac-LDL). Afterward,5x10(6) hESC-ECs treated for 24 hours with nicotine (10(-8) M) or PBS (as control) were injected into the hearts of mice undergoing LAD ligation followed by administration for two weeks of vehicle or nicotine (100 microg/ml) in the drinking water. Surprisingly,bioluminescence imaging (BLI) showed significant improvement in the survival of transplanted hESC-ECs in the nicotine treated group at 6 weeks. Postmortem analysis confirmed increased presence of small capillaries in the infarcted zones. Finally,in vitro mechanistic analysis suggests activation of the MAPK and Akt pathways following activation of nicotinic acetylcholine receptors (nAChRs).backslashnbackslashnCONCLUSIONS: This study shows for the first time that short-term systemic administrations of low dose nicotine can improve the survival of transplanted hESC-ECs,and enhance their angiogenic effects in vivo. Furthermore,activation of nAChRs has anti-apoptotic,angiogenic,and proliferative effects through MAPK and Akt signaling pathways. View Publication

Antiangiogenic effects of the proteasome inhibitor bortezomib were analyzed on tumor xenografts in vivo. Bortezomib strongly inhibited angiogenesis and vascularization in the chicken chorioallantoic membrane. Bortezomib's inhibitory effects on chorioallantoic membrane vascularization were abrogated in the presence of distinct tumor xenografts,thanks to a soluble factor secreted by tumor cells. Through size-exclusion and ion-exchange chromatography as well as mass spectroscopy,we identified GRP-78,a chaperone protein of the unfolded protein response,as being responsible for bortezomib resistance. Indeed,a variety of bortezomib-resistant solid tumor cell lines (PC-3,HRT-18),but not myeloma cell lines (U266,OPM-2),were able to secrete high amounts of GRP-78. Recombinant GRP-78 conferred bortezomib resistance to endothelial cells and OPM-2 myeloma cells. Knockdown of GRP78 gene expression in tumor cells and immunodepletion of GRP-78 protein from tumor cell supernatants restored bortezomib sensitivity. GRP-78 did not bind or complex bortezomib but induced prosurvival signals by phosphorylation of extracellular signal-related kinase and inhibited p53-mediated expression of proapoptotic Bok and Noxa proteins in endothelial cells. From our data,we conclude that distinct solid tumor cells are able to secrete GRP-78 into the tumor microenvironment,thus demonstrating a hitherto unknown mechanism of resistance to bortezomib. View Publication

Adipose tissue-derived stem cells have been demonstrated to differentiate into cardiomyocytes and vascular endothelial cells. Here we investigate whether mature adipocyte-derived dedifferentiated fat (DFAT) cells can differentiate to cardiomyocytes in vitro and in vivo by establishing DFAT cell lines via ceiling culture of mature adipocytes. DFAT cells were obtained by dedifferentiation of mature adipocytes from GFP-transgenic rats. We evaluated the differentiating ability of DFAT cells into cardiomyocytes by detection of the cardiac phenotype markers in immunocytochemical and RT-PCR analyses in vitro. We also examined effects of the transplantation of DFAT cells into the infarcted heart of rats on cardiomyocytes regeneration and angiogenesis. DFAT cells expressed cardiac phenotype markers when cocultured with cardiomyocytes and also when grown in MethoCult medium in the absence of cardiomyocytes,indicating that DFAT cells have the potential to differentiate to cardiomyocyte lineage. In a rat acute myocardial infarction model,transplanted DFAT cells were efficiently accumulated in infarcted myocardium and expressed cardiac sarcomeric actin at 8 weeks after the cell transplantation. The transplantation of DFAT cells significantly (ptextless0.05) increased capillary density in the infarcted area when compared with hearts from saline-injected control rats. We demonstrated that DFAT cells have the ability to differentiate to cardiomyocyte-like cells in vitro and in vivo. In addition,transplantation of DFAT cells led to neovascuralization in rats with myocardial infarction. We propose that DFAT cells represent a promising candidate cell source for cardiomyocyte regeneration in severe ischemic heart disease. View Publication

Endoglin is an accessory receptor for TGF-beta signaling and is required for normal hemangioblast,early hematopoietic,and vascular development. We have previously shown that an upstream enhancer,Eng -8,together with the promoter region,mediates robust endothelial expression yet is inactive in blood. To identify hematopoietic regulatory elements,we used array-based methods to determine chromatin accessibility across the entire locus. Subsequent transgenic analysis of candidate elements showed that an endothelial enhancer at Eng +9 when combined with an element at Eng +7 functions as a strong hemato-endothelial enhancer. Chromatin immunoprecipitation (ChIP)-chip analysis demonstrated specific binding of Ets factors to the promoter as well as to the -8,+7+9 enhancers in both blood and endothelial cells. By contrast Pu.1,an Ets factor specific to the blood lineage,and Gata2 binding was only detected in blood. Gata2 was bound only at +7 and GATA motifs were required for hematopoietic activity. This modular assembly of regulators gives blood and endothelial cells the regulatory freedom to independently fine-tune gene expression and emphasizes the role of regulatory divergence in driving functional divergence. View Publication

Adipose tissue development is associated with neovascularization,which might be exploited therapeutically. We investigated the neovasculogenesis antigenic profile and kinetics in adipose tissue-derived stromal cells (ADSCs) to understand the potential of ADSCs to generate new vessels. Murine and human visceral adipose tissues were processed with collagenase to obtain ADSCs from the stromal vascular fraction. Freshly isolated murine and human ADSCs featured the expression of early markers of endothelial differentiation [uptake of DiI-labeled acetylated LDL,CD133,CD34,kinase insert domain receptor (KDR)],but not markers for more mature endothelial cells (CD31 and von Willebrand factor). In methylcellulose medium,multilocular cells positive for Oil Red O staining appeared after 6 days. After 10 days,clusters of ADSCs spontaneously formed branched tubelike structures,which were strongly positive for CD34 and CD31,while losing their ability to undergo adipocyte differentiation. In Matrigel,in the presence of endothelial growth factors ADSCs formed branched tubelike structures. By clonal assays in methylcellulose we also determined the frequency of granulocyte-macrophage (CFU-GM) and erythroid (BFU-E) colony-forming units from ADSCs,compared with bone marrow-derived stromal cells (BMSCs) used as a positive control. After 4-14 days,BMSCs formed 8 +/- 3 BFU-E and 40 +/- 10 CFU-GM,while ADSCs never produced colonies of myeloid progenitors. The developing adipose tissue has neovasculogenic potential,based on the recruitment of local rather than circulating progenitors. Adipose tissue might therefore be a viable autonomous source of cells for postnatal neovascularization. View Publication