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Retinal vascular damages are the cardinal hallmarks of retinopathy of prematurity (ROP),a leading cause of vision impairment and blindness in childhood. Both angiogenesis and vasculogenesis are disrupted in the hyperoxia-induced vaso-obliteration phase,and recapitulated,although aberrantly,in the subsequent ischemia-induced neovessel formation phase of ROP. Yet,whereas the histopathological features of ROP are well characterized,many key modulators with a therapeutic potential remain unknown. The CCN1 protein also known as cysteine-rich protein 61 (Cyr61) is a dynamically expressed,matricellular protein required for proper angiogenesis and vasculogenesis during development. The expression of CCN1 becomes abnormally reduced during the hyperoxic and ischemic phases of ROP modeled in the mouse eye with oxygen-induced retinopathy (OIR). Lentivirus-mediated re-expression of CCN1 enhanced physiological adaptation of the retinal vasculature to hyperoxia and reduced pathological angiogenesis following ischemia. Remarkably,injection into the vitreous of OIR mice of hematopoietic stem cells (HSCs) engineered to express CCN1 harnessed ischemia-induced neovessel outgrowth without adversely affecting the physiological adaptation of retinal vessels to hyperoxia. In vitro exposure of HSCs to recombinant CCN1 induced integrin-dependent cell adhesion,migration,and expression of specific endothelial cell markers as well as many components of the Wnt signaling pathway including Wnt ligands,their receptors,inhibitors,and downstream targets. CCN1-induced Wnt signaling mediated,at least in part,adhesion and endothelial differentiation of cultured HSCs,and inhibition of Wnt signaling interfered with normalization of the retinal vasculature induced by CCN1-primed HSCs in OIR mice. These newly identified functions of CCN1 suggest its possible therapeutic utility in ischemic retinopathy. View Publication

OBJECTIVE: The role of semaphorins in tumor progression is still poorly understood. In this study,we aimed at elucidating the regulatory role of semaphorin 3A (SEMA3A) in primary tumor growth and metastatic dissemination. METHODS AND RESULTS: We used 3 different experimental approaches in mouse tumor models: (1) overexpression of SEMA3A in tumor cells,(2) systemic expression of SEMA3A following liver gene transfer in mice,and (3) tumor-targeted release of SEMA3A using gene modified Tie2-expressing monocytes as delivery vehicles. In each of these experimental settings,SEMA3A efficiently inhibited tumor growth by inhibiting vessel function and increasing tumor hypoxia and necrosis,without promoting metastasis. We further show that the expression of the receptor neuropilin-1 in tumor cells is required for SEMA3A-dependent inhibition of tumor cell migration in vitro and metastatic spreading in vivo. CONCLUSIONS: In sum,both systemic and tumor-targeted delivery of SEMA3A inhibits tumor angiogenesis and tumor growth in multiple mouse models; moreover,SEMA3A inhibits the metastatic spreading from primary tumors. These data support the rationale for further investigation of SEMA3A as an anticancer molecule. View Publication

Recent studies have demonstrated that cancer stem cells play an important role in the pathobiology of head and neck squamous cell carcinomas (HNSCC). However,little is known about functional interactions between head and neck cancer stem-like cells (CSC) and surrounding stromal cells. Here,we used aldehyde dehydrogenase activity and CD44 expression to sort putative stem cells from primary human HNSCC. Implantation of 1,000 CSC (ALDH+CD44+Lin-) led to tumors in 13 (out of 15) mice,whereas 10,000 noncancer stem cells (ALDH-CD44-Lin-) resulted in 2 tumors in 15 mice. These data demonstrated that ALDH and CD44 select a subpopulation of cells that are highly tumorigenic. The ability to self-renew was confirmed by the observation that ALDH+CD44+Lin- cells sorted from human HNSCC formed more spheroids (orospheres) in 3-D agarose matrices or ultra-low attachment plates than controls and were serially passaged in vivo. We observed that approximately 80% of the CSC were located in close proximity (within 100-μm radius) of blood vessels in human tumors,suggesting the existence of perivascular niches in HNSCC. In vitro studies demonstrated that endothelial cell-secreted factors promoted self-renewal of CSC,as demonstrated by the upregulation of Bmi-1 expression and the increase in the number of orospheres as compared with controls. Notably,selective ablation of tumor-associated endothelial cells stably transduced with a caspase-based artificial death switch (iCaspase-9) caused a marked reduction in the fraction of CSC in xenograft tumors. Collectively,these findings indicate that endothelial cell-initiated signaling can enhance the survival and self-renewal of head and neck CSC. View Publication

The physiologic roles of angiopoietin-like proteins (Angptls) in the hematopoietic system remain unknown. Here we show that hematopoietic stem cells (HSCs) in Angptl3-null mice are decreased in number and quiescence. HSCs transplanted into Angptl3-null recipient mice exhibited impaired repopulation. Bone marrow sinusoidal endothelial cells express high levels of Angptl3 and are adjacent to HSCs. Importantly,bone marrow stromal cells or endothelium deficient in Angptl3 have a significantly decreased ability to support the expansion of repopulating HSCs. Angptl3 represses the expression of the transcription factor Ikaros,whose unregulated overexpression diminishes the repopulation activity of HSCs. Angptl3,as an extrinsic factor,thus supports the stemness of HSCs in the bone marrow niche. View Publication

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

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