C-Reactive Protein in Atherothrombosis and Angiogenesis

C-reactive protein (CRP) is a short pentraxin mainly found as a pentamer in the circulation, or as non-soluble monomers CRP (mCRP) in tissues, exerting different functions. This review is focused on discussing the role of CRP in cardiovascular disease, including recent advances on the implication of CRP and its forms specifically on the pathogenesis of atherothrombosis and angiogenesis. Besides its role in the humoral innate immune response, CRP contributes to cardiovascular disease progression by recognizing and binding multiple intrinsic ligands. mCRP is not present in the healthy vessel wall but it becomes detectable in the early stages of atherogenesis and accumulates during the progression of atherosclerosis. CRP inhibits endothelial nitric oxide production and contributes to plaque instability by increasing endothelial cell adhesion molecules expression, by promoting monocyte recruitment into the atheromatous plaque and by enzymatically binding to modified low-density lipoprotein. CRP also contributes to thrombosis, but depending on its form it elicits different actions. Pentameric CRP has no involvement in thrombogenesis, whereas mCRP induces platelet activation and thrombus growth. In addition, mCRP has apparently contradictory pro-angiogenic and anti-angiogenic effects determining tissue remodeling in the atherosclerotic plaque and in infarcted tissues. Overall, CRP contributes to cardiovascular disease by several mechanisms that deserve an in-depth analysis.

A role for Hox A5 in regulating angiogenesis and vascular patterning

BACKGROUND

Homeobox (Hox) genes are transcriptional regulators which modulate embryonic morphogenesis and pathological tissue remodeling in adults via regulation of genes associated with cell-cell or cell extracellular matrix (ECM) interactions. We previously showed that while Hox 3 genes promote angiogenesis, Hox D10 inhibits this process.

METHODS AND RESULTS

Here we show that another Hox family gene, Hox A5, also blocks angiogenesis but accomplishes this by targeting different downstream genes than Hox D10. Sustained expression of Hox A5 leads to down regulation of many pro-angiogenic genes including VEGFR2, ephrin A1, Hif1alpha and COX-2. In addition, Hox A5 also upregulates expression of anti-angiogenic genes including Thrombospondin-2. Furthermore, we show that while Hox A5 mRNA is expressed in quiescent endothelial cells (EC), its expression is diminished or absent in active angiogenic EC found in association with breast tumors or in proliferating infantile hemangiomas.

CONCLUSIONS

Together our results suggest that restoring Hox A5 expression may provide a novel means to limit breast tumor growth or expansion of hemangiomas.

Homeobox D10 Induces Phenotypic Reversion of Breast Tumor Cells in a Three-Dimensional Culture Model

Homeobox (Hox) genes are master regulatory genes that direct organogenesis and maintain differentiated tissue function. We previously reported that HoxD10 helps to maintain a quiescent, differentiated phenotype in endothelial cells by suppressing expression of genes involved in remodeling the extracellular matrix and cell migration. Here we investigated whether HoxD10 could also promote or maintain a differentiated phenotype in epithelial cells. We observed that HoxD10 expression is progressively reduced in epithelial cells as malignancy increases in both breast and endometrial tumors. Retroviral gene transfer to restore expression of HoxD10 in the malignant breast tumor cells MDA-MB-231 significantly impaired migration, and when these cells were cultured in a three-dimensional laminin-rich basement membrane (3DlrBM) model, they formed polarized, acinar structures. This phenotypic reversion was accompanied by decreased alpha3 integrin expression and reduced proliferation. Importantly, expression of HoxD10 in the MDA-MB-231 cells inhibited their ability to form tumors in mouse xenografts. Taken together, our results suggest that HoxD10 has tumor-suppressive functions for mammary epithelial cells.

MicroRNA-145 Regulates the Differentiation of Adipose Stem Cells Toward Microvascular Endothelial Cells and Promotes Angiogenesis

RATIONALE

Adipose-derived stem cells (ASCs) are a potential adult mesenchymal stem cell source for restoring endothelial function in ischemic tissues. However, the mechanism that promotes ASCs differentiation toward endothelial cells (ECs) is not known.

OBJECTIVE

To investigate the mechanisms of ASCs differentiation into ECs.

METHODS AND RESULTS

ASCs were isolated from clinical lipoaspirates and cultured with DMEM or endothelial cell-conditioned medium. Endothelial cell-conditioned medium induced downregulation of miR-145 in ASCs and promoted endothelial differentiation. We identified bFGF (basic fibroblast growth factor) released by ECs as inducer of ASCs differentiation through receptor-induced AKT (protein kinase B) signaling and phosphorylation of FOXO1 (forkhead box protein O1) suppressing its transcriptional activity and decreasing miR-145 expression. Blocking bFGF-receptor or PI3K/AKT signaling in ASCs increased miR-145 levels. Modulation of miR-145 in ASCs, using a miR-145 inhibitor, regulated their differentiation into ECs: increasing proliferation, migration, inducing expression of EC markers (VE-cadherin, VEGFR2 [vascular endothelial growth factor receptor 2], or VWF [von Willebrand Factor]), and tube-like formation. Furthermore, in vivo, downregulation of miR-145 in ASCs enhanced angiogenesis in subcutaneously implanted plugs in mice. In a murine hindlimb ischemia model injection of ASCs with downregulated miR-145 induced collateral flow and capillary formation evidenced by magnetic resonance angiography. Next, we identified ETS1 (v-ets avian erythroblastosis virus E26 oncogene homolog 1) as the target of miR-145. Upregulation of miR-145 in ASCs, by mimic miR-145, suppressed ETS1 expression and consequently abolished EC differentiation and the angiogenic properties of endothelial cell-conditioned medium-preconditioned ASCs; whereas, overexpression of ETS1 reversed the abrogated antiangiogenic capacity of miR-145. ETS1 overexpression induced similar results to those obtained with miR-145 knockdown.

CONCLUSIONS

bFGF released by ECs induces ASCs differentiation toward ECs through miR-145-regulated expression of ETS1. Downregulation of miR-145 in ASCs induce vascular network formation in ischemic muscle.

Microvesicles in Atherosclerosis and Angiogenesis: From Bench to Bedside and Reverse

Atherosclerosis (AT) is a progressive chronic disease involving lipid accumulation, fibrosis, and inflammation in medium and large-sized arteries, and it is the main cause of cardiovascular disease (CVD). AT is caused by dyslipidemia and mediated by both innate and adaptive immune responses. Despite lipid-lowering drugs have shown to decrease the risk of cardiovascular events (CVEs), there is a significant burden of AT-related morbidity and mortality. Identification of subjects at increased risk for CVE as well as discovery of novel therapeutic targets for improved treatment strategies are still unmet clinical needs in CVD. Microvesicles (MVs), small extracellular plasma membrane particles shed by activated and apoptotic cells have been widely linked to the development of CVD. MVs from vascular and resident cells by facilitating exchange of biological information between neighboring cells serve as cellular effectors in the bloodstream and play a key role in all stages of disease progression. This article reviews the current knowledge on the role of MVs in AT and CVD. Attention is focused on novel aspects of MV-mediated regulatory mechanisms from endothelial dysfunction, vascular wall inflammation, oxidative stress, and apoptosis to coagulation and thrombosis in the progression and development of atherothrombosis. MV contribution to vascular remodeling is also discussed, with a particular emphasis on the effect of MVs on the crosstalk between endothelial cells and smooth muscle cells, and their role regulating the active process of AT-driven angiogenesis and neovascularization. This review also highlights the latest findings and main challenges on the potential prognostic, diagnostic, and therapeutic value of cell-derived MVs in CVD. In summary, MVs have emerged as new regulators of biological functions in atherothrombosis and might be instrumental in cardiovascular precision medicine; however, significant efforts are still needed to translate into clinics the latest findings on MV regulation and function.

Angiogenic microvascular endothelial cells release microparticles rich in tissue factor that promotes postischemic collateral vessel formation

OBJECTIVE

Therapeutic angiogenesis is a promising strategy for treating ischemia. Our previous work showed that endogenous endothelial tissue factor (TF) expression induces intracrine signaling and switches-on angiogenesis in microvascular endothelial cells (mECs). We have hypothesized that activated mECs could exert a further paracrine regulation through the release of TF-rich microvascular endothelial microparticles (mEMPs) and induce neovascularization of ischemic tissues.

APPROACH AND RESULTS

Here, we describe for the first time that activated mECs are able to induce reparative neovascularization in ischemic zones by releasing TF-rich microparticles. We show in vitro and in vivo that mEMPs released by both wild-type and TF-upregulated-mECs induce angiogenesis and collateral vessel formation, whereas TF-poor mEMPs derived from TF-silenced mECs are not able to trigger angiogenesis. Isolated TF-bearing mEMPs delivered to nonperfused adductor muscles in a murine hindlimb ischemia model enhance collateral flow and capillary formation evidenced by MRI. TF-bearing mEMPs increase angiogenesis operating via paracrine regulation of neighboring endothelial cells, signaling through the β1-integrin pathway Rac1-ERK1/2-ETS1 and triggering CCL2 (chemokine [C-C motif] ligand 2) production to form new and competent mature neovessels.

CONCLUSIONS

These findings demonstrate that TF-rich mEMPs released by microvascular endothelial cells can overcome the consequences of arterial occlusion and tissue ischemia by promoting postischemic neovascularization and tissue reperfusion.

HoxA5 stabilizes adherens junctions via increased Akt1

Normal vascular development and angiogenesis is regulated by coordinated changes in cell-cell and cell-extracellular matrix (ECM) interactions. The Homeobox (Hox) family of transcription factors coordinately regulate expression of matrix degrading proteinases, integrins and ECM components and profoundly impact vascular remodeling. Whereas HoxA5 is down regulated in active angiogenic endothelial cells (EC), sustained expression of HoxA5 induces TSP-2 and blocks angiogenesis. Since HoxA5 is also lacking in EC in proliferating hemangiomas, we investigated whether restoring expression of HoxA5 could normalize hemangioma cell morphology and/or behavior. Sustained expression of HoxA5 in the murine hemangioma cell line (EOMA) reduced their growth in vivo and promoted branching morphogenesis in 3D BM cultures. Moreover, restoring HoxA5 expression increased the retention of beta-catenin in adherens junctions and reduced permeability. In addition we also show that the HoxA5 mediated increase in stability of adherens junctions requires Akt1 activity and introduction of constitutively active myr-Akt in EOMA cells also increased retention of beta-catenin in adherens junctions. Finally we show that HoxA5 increases Akt1 mRNA, protein expression and further enhances Akt activity via a coordinate down regulation of PTEN. Together these results demonstrate a central role for HoxA5 in coordinating a stable vascular phenotype.

Tissue Factor Regulates Microvessel Formation and Stabilization by Induction of Chemokine (C-C motif) Ligand 2 Expression

Objective—

Tissue factor (TF) triggers arterial thrombosis. TF is also able to initiate cellular signaling mechanisms leading to angiogenesis. Because high cardiovascular risk atherosclerotic plaques show significant angiogenesis, our objective was to investigate whether TF is able to trigger and stabilize atherosclerotic plaque neovessel formation.

Methods and Results—

In this study, we showed, by real-time confocal microscopy in 3-dimensional basement membrane cocultures, that TF in human microvascular endothelial cells (HMEC-1) and in human vascular smooth muscle cells (HVSMCs) plays an important role in the formation of capillary-like networks. TF silencing in endothelial cells and smooth muscle cells inhibits the formation of tube-like structures with stable phenotype. Using an in vivo model, we observed that TF inhibition in either HMEC-1 or HVSMCs reduced their shared ability to form new capillaries. The phenotypic changes induced by TF silencing were linked to reduced chemokine (C-C motif) ligand 2 (CCL2) expression in endothelial cells. Wound healing and chemotactic assays demonstrated that TF-induced release of CCL2 stimulated HVSMC migration to HMEC-1.

Conclusion—

Endogenous TF regulates CCL2 production in endothelial cells. Secreted CCL2 mediates the angiogenic effect of TF by recruiting smooth muscle cells toward endothelial cells and facilitates the maturation of newly formed microvessels.

Retroviral delivery of homeobox D3 gene induces cerebral angiogenesis in mice

Angiogenesis is regulated by concerted actions of angiogenic and angiostatic factors. Homeobox D3 gene (HOXD3) is a potent proangiogenic transcription factor that promotes angiogenesis by modulating the expression of matrix-degrading proteinases, integrins, and extracellular matrix components. Application of HOXD3 can promote angiogenesis in the skin, but its role in other vascular beds has not been examined. The authors examined HOXD3 expression in human brain vessels by in situ hybridization. Although little or no HOXD3 mRNA was detected in normal brain vessels, increased levels of HOXD3 and its target gene, alpha V beta 3, were found in angiogenic vessels in human brain arteriovenous malformations. The authors further investigated whether HOXD3 plays a role in cerebral angiogenesis in a murine model. Expression of HOXD3 in mouse brain was achieved through retroviral vector-mediated HOXD3 gene transfer. HOXD3 expression lead to a significant induction of cerebral angiogenesis as shown by quantitative microvessel counting (HOXD3: 241 +/- 19 vessels/mm2 vs. saline: 150 +/- 14 vessels/mm2, P < 0.05). The data also showed that focal cerebral blood flow was increased in the angiogenic region with less vascular leakage. Moreover, expression of HOXD3 led to an increase in the expression of a direct downstream target gene alpha V beta 3 integrin. The data suggest that HOXD3 may play an important role in regulating cerebral angiogenesis, and that gene transfer of HOXD3 may provide a novel and potent means to stimulate angiogenesis.

Monocyte-secreted Wnt5a interacts with FZD5 in microvascular endothelial cells and induces angiogenesis through tissue factor signaling

Angiogenesis during reactive and pathologic processes is characteristically associated with inflammation. Inflammatory cells participate in angiogenesis by secreting different molecules that affect endothelial cell functions. We had previously shown that induced tissue factor (TF) expression in activated microvascular endothelial cells (mEC) is able to induce angiogenesis via autocrine regulation. However, the signals that induce TF expression in mEC are not fully known. Here, we demonstrate that monocyte paracrine cross-talk with mECs triggers mEC-TF expression. We have identified that monocyte-secreted Wnt5a induces TF expression in mEC and functionally induces cell monolayer repair and angiotube formation in vitro as well as microvessel formation in vivo. Monocyte-secreted Wnt5a activates FZD5 in mECs, which signals to induce the release of intracellular Ca(2+) and increase NFκB transcription activity and TF gene expression. In sum, Wnt5a secreted by monocytes signals through the noncanonical Wnt-FZD5 pathway in mECs to induce TF expression that induces angiogenesis by autocrine regulation.

Subcellular localization of tissue factor and human coronary artery smooth muscle cell migration

BACKGROUND

Tissue factor (TF) is the most relevant physiological trigger of thrombosis. Additionally TF is a transmembrane receptor with cell signaling functions.

OBJECTIVES

The aim of this study was to investigate TF subcellular localization, function and signaling in human coronary artery smooth muscle cell migration.

METHODS

Coronary arteries and primary cultures of vascular smooth muscle cells (HVSMC) were obtained from human explanted hearts. Wound repair and Boyden chamber assays were used to measure migration in vitro. TF-pro-coagulant activity (TF-PCA) was measured in extracted cellular membranes. Analysis of TF distribution was performed by confocal microscopy. A nucleofector device was used for TF and protease activated receptor 2 (PAR2) silencing. mRNA levels were analyzed by RT-PCR.

RESULTS

In migrating HVSMC TF translocates to the leading edge of the cells showing an intense patch-like staining in the lamellipodia. In the migrating front TF colocalizes with filamin (FLN) in the polarized lipid rafts. TF-PCA was increased in migrating cells. Silencing of the TF gene inhibits RSK-induced FLN-Ser-2152 phosphorylation, down-regulates CDC42, RhoA, and Rac1 protein expression and significantly inhibits cell migration. Silencing PAR2 also inhibits cell migration; however, silencing both TF and PAR2 induces a significantly higher effect on migration. Smooth muscle cells expressing TF have been identified in non-lipid-rich human coronary artery atherosclerotic plaques.

CONCLUSIONS

TF translocates to the cell front in association with cytoskeleton proteins and regulates HVSMC migration by mechanisms dependent and independent of factor (F)VIIa/PAR2. These results extend the functional role of TF to smooth muscle cell trafficking in vessel wall remodeling.

Tissue factor-Akt signaling triggers microvessel formation

BACKGROUND

Tissue factor (TF) and its signaling mediators play a crucial role in angiogenesis. We have previously shown that TF-induced endothelial cell (EC) CCL2 release contributes to neovessel formation.

OBJECTIVE

In this study, we have investigated the signaling pathways involved in TF-induced EC tube formation.

METHODS

The human microvascular endothelial cell line (HMEC-1) cultured onto basement membrane-like gel (Matrigel) was used to study TF signaling pathways during neovessels formation.

RESULTS

Inhibition of endogenous TF expression in ECs using siRNA resulted in inhibition of a stable tube-like structure formation in three-dimensional cultures, associated with a down-regulation of Akt activation, an increased phosphorylation of Raf at Ser(259) with a subsequent reduction of Raf kinase and a reduction of ERK1/2 phosphorylation ending up in Ets-1 transcription factor inhibition. Conversely, overexpression of TF resulted in an increase in tube formation and up-regulation of Akt protein. Moreover, immunoprecipitation of Akt and western blotting of the immunoprecipitates with anti-TF antibody revealed a direct interaction between TF and Akt. The effects of silencing TF were partially reversed by a PAR2 agonist that rescued tube formation, indicating that the TF-Akt pathway induces PAR2-independent effector signaling. Finally, enforced expression of Akt in TF-silenced ECs rescued tube formation in a Matrigel assay and induced Ets-1 phosphorylation.

CONCLUSIONS

In EC, TF forms a complex with Akt activating Raf/ERK and Ets-1 signaling induces microvessel formation.

High-density lipoprotein remodelled in hypercholesterolaemic blood induce epigenetically driven down-regulation of endothelial HIF-1α expression in a preclinical animal model

AIMS

High-density lipoproteins (HDLs) are circulating micelles that transport proteins, lipids, and miRNAs. HDL-transported miRNAs (HDL-miRNAs) have lately received attention but their effects on vascular cells are not fully understood. Additionally, whether cardiovascular risk factors affect HDL-miRNAs levels and miRNA transfer to recipient cells remains equally poorly known. Here, we have investigated the changes induced by hypercholesterolaemia on HDL-miRNA levels and its effect on recipient endothelial cells (ECs).

METHODS AND RESULTS

Pigs were kept on a high-fat diet (HC; n = 10) or a normocholesterolaemic chow (NC; n = 10) for 10 days reaching cholesterol levels of 321.0 (229.7-378.5) mg/dL and 74.0 (62.5-80.2) mg/dL, respectively. HDL particles were isolated, purified, and quantified. HDL-miRNA profiling (n = 149 miRNAs) of HC- and NC-HDLs was performed by multipanel qPCR. Cell cultures of porcine aortic ECs were used to determine whether HDL-miRNAs were delivered to ECs. Potential target genes modulated by miRNAs were identified by bioinformatics and candidate miRNAs were validated by molecular analysis. In vivo effects in the coronary arteries of normocholesterolaemic swine administered HC- or NC-HDLs were analysed. Among the HDL-miRNAs, four were found in different amounts in HC- and NC-HDL (P < 0.05). miR-126-5p and -3p and miR-30b-5p (2.7×, 1.7×, and 1.3×, respectively) were found in higher levels and miR-103a-3p and miR-let-7g-5p (-1.6×, -1.4×, respectively) in lower levels in HC-HDL. miR-126-5p and -3p were transferred from HC-HDL to EC (2.5×; P < 0.05), but not from NC-HDL, by a SRB1-mediated mechanism. Bioinformatics revealed that HIF1α was the miR-126 target gene with the highest predictive value, which was accordingly found to be markedly reduced in HC-HDL-treated ECs and in miR126 mimic transfected ECs. In vivo validation confirmed that HIF1α was diminished in the coronary endothelial layer of NC pigs administered HC-HDL vs. those administered NC-HDL (P < 0.05).

CONCLUSION

Hypercholesterolaemia induces changes in the miRNA content of HDL enhancing miR126 and its delivery to ECs with the consequent down-regulation of its target gene HIF1α.

Extracellular vesicles in atherothrombosis: From biomarkers and precision medicine to therapeutic targets

Atherosclerotic cardiovascular disease (ASCVD) remains the leading cause of global mortality. Extracellular vesicles (EVs) are small phospholipid vesicles that convey molecular bioactive cargoes and play essential roles in intercellular communication and, hence, a multifaceted role in health and disease. The present review offers a glimpse into the current state and up-to-date concepts on EV field. It also covers their association with several cardiovascular risk factors and ischemic conditions, being subclinical atherosclerosis of utmost relevance for prevention. Interestingly, we show that EVs hold promise as prognostic and diagnostic as well as predictive markers of ASCVD in the precision medicine era. We then report on the role of EVs in atherothrombosis, disentangling the mechanisms involved in the initiation, progression, and complication of atherosclerosis and showing their direct effect in the context of arterial thrombosis. Finally, their potential use for therapeutic intervention is highlighted.

Ets-1 transcription is required in tissue factor driven microvessel formation and stabilization

Tissue factor (TF) has well-recognized roles as initiator of blood coagulation as well as an intracellular signaling receptor. TF signaling regulates gene transcription and protein translation. Recently, we have shown that TF-induced mature neovessel formation is ultimately driven by CCL2 expression. However, the signaling process induced by TF to promote microvessel formation remains to be determined. This study was designed with the objective to investigate the mechanisms involved in TF-induced neovessel formation. Here, we have identified that Ets-1 expression is a downstream effector of TF signaling. TF-siRNA induced a highly significant reduction in Ets-1 expression levels and in Ets-1/DNA binding while inducing abrogation of microvessel formation. Activation of Ets-1 rescued the effect of TF inhibition and restored microvessel formation confirming the critical role of Ets-1 in TF-induced angiogenesis. VE-cadherin expression, a key regulator of endothelial intercellular junctions, and an Ets-1 target molecule was dependent of TF-inhibition. We show that TF signals through ERK1/2 to activate Ets-1 and induce CCL2 gene expression by binding to its promoter region. We conclude that endothelial cell TF signals through ERK1/2 and Ets-1 to trigger microvessel formation.

Allogenic adipose-derived stem cell therapy overcomes ischemia-induced microvessel rarefaction in the myocardium: systems biology study

Background

Myocardial microvascular loss after myocardial infarction (MI) remains a therapeutic challenge. Autologous stem cell therapy was considered as an alternative; however, it has shown modest benefits due to the impairing effects of cardiovascular risk factors on stem cells. Allogenic adipose-derived stem cells (ASCs) may overcome such limitations, and because of their low immunogenicity and paracrine potential may be good candidates for cell therapy. In the present study we investigated the effects of allogenic ASCs and their released products on cardiac rarefaction post MI.

Methods

Pig subcutaneous adipose tissue ASCs were isolated, expanded and GFP-labeled. ASC angiogenic function was assessed by the in-vivo chick chorioallantoic membrane (CAM) model. Pigs underwent MI induction and 7 days after were randomized to receive: allogenic ASCs (intracoronary infusion); conditioned media (CM; intravenous infusion); ASCs + CM; or PBS/placebo (control). Cardiac damage and function were monitored by 3-T cardiac magnetic resonance imaging upon infusion (baseline CMR) and 1 and 3 weeks thereafter. We assessed in the myocardium: microvessel density; angiogenic markers (CD105, CD31, TF, VEGFR2, VEGFR1, vWF, eNOS, CD62); collagen deposition; and reparative fibrosis (TGFβ/TβRII/collagen). Differential proteomics of ASCs and CM was performed to characterize the ASC protein signature.

Results

CAM indicated a significant ASC proangiogenic capacity. In pigs after MI, only PBS/placebo animals displayed an impaired cardiac function 3 weeks after infusion (p < 0.05 vs baseline). Administration of ASCs + CM significantly enhanced neovessel formation and favored cardiac repair post MI (p < 0.05 vs the other groups). Molecular markers of angiogenesis were significantly upregulated both at transcriptional and protein levels (p < 0.05). The in-silico bioinformatics analysis of the ASC and CM proteome (interactome) indicated activation of a coordinated protein network involved in the formation of microvessels and the resolution of rarefaction.

Conclusion

Coadministration of allogenic ASCs and their CM synergistically contribute to the neovascularization of the infarcted myocardium through a coordinated upregulation of the proangiogenic protein interactome.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0509-2) contains supplementary material, which is available to authorized users.

PAR2-SMAD3 in microvascular endothelial cells is indispensable for vascular stability via tissue factor signaling

Tissue factor (TF) signaling regulates gene expression and protein synthesis leading to the modulation of cell function. Recently, we have demonstrated in microvascular endothelial cells (mECs) that TF signaling induces activation of ETS1 transcription factor. Because combinatorial control is a characteristic property of ETS family members, involving the interaction between ETS1 and other transcription factors, here we investigate whether additional transcription factors are involved in TF-induced angiogenesis. We show by in vitro and in vivo experiments that in addition to ETS1, SMAD3 contributes to tube-like stabilization induced by TF in mECs. Whereas the ability of TF-overexpressing cells to induce gene expression through ETS1 is dependent on AKT signaling, SMAD3 induces ETS1 by an alternative AKT-independent pathway. Moreover, while TF-AKT-ETS1 pathway to induce CCL2 is PAR2-independent, PAR2 is required for TF-SMAD3-induced CCL2 expression. PAR2-dependent activation of SMAD3 is mediated by PKC phosphorylation. In addition, disruption of SMAD3 expression in mECs reduces ERK1/2 phosphorylation and decreases target gene promoter activity. In conclusion, in mECs TF-induced angiogenesis seems to be the result of two signaling pathways: TF-induced microvessel formation is regulated through β1 integrin-AKT-ETS1; and TF-induced microvessel stabilization is regulated via PAR2-SMAD3 that is indispensable for the maintenance of vascular integrity.

CD142+/CD61+, CD146+ and CD45+ microparticles predict cardiovascular events in high risk patients following a Mediterranean diet supplemented with nuts

Circulating microparticles (cMPs) are small phospholipid-rich microvesicles shed by activated cells that play a pivotal role in cell signalling related to the pathogenesis of atherothrombosis. We aimed to investigate the prognostic value of cMPs released from different vascular cells for cardiovascular event (CVE) presentation in asymptomatic patients at high cardiovascular risk factors under nutritional and pharmacologic treatment. This is a nested case-control study of 50 patients from the five-year follow-up prospective PREDIMED trial enrolled in the nuts arm of the Mediterranean diet (MedDiet-nuts). We randomly selected 25 patients who had suffered a CVE during follow-up and pair-matched them for sex, age, and classical CV risk factors to 25 patients who remained asymptomatic (no-CVE). Total Annexin V-(AV)+ cMPs and cMPs from cells of the vascular compartment were quantified by flow cytometry at baseline and after one year follow-up. MedDiet-nuts and pharmacological treatment neither modified levels nor source of MP shedding in CVE patients. However, no-CVE patients showed 40-86 % decreased total AV+, PAC-1+/AV+, CD61+/AV+, CD142+/CD61+/AV+, CD62P+/AV+, CD146+/AV+, CD63+/AV+ and CD11a+/AV+ cMPs at one year follow-up (p≤0.046, all). CD142+/CD61+/AV+, CD146+/AV+ and CD45+/AV+ cMPs were decreased in no-CVE patients compared to CVE patients. A ROC-curve clustered model for CD142+/CD61+/AV+, CD45+/AV+ and CD146+/AV+ cMPs predicted a future CVE [p<0.0001, AUC=0.805 (0.672 to 0.938)]. In patients at high CV risk profile treated with a controlled MedDiet supplemented with nuts and receiving up-to-date CV drug treatment, reduced cMPs derived from activated platelets, leukocytes and endothelial cells are predictive of protection against CVE within the next four years.

mCRP triggers angiogenesis by inducing F3 transcription and TF signalling in microvascular endothelial cells

Inflammation contributes to vascular disease progression. However, the role of circulating inflammatory molecules on microvascular endothelial cell (mECs) is not fully elucidated. The aim of this study was to investigate the effects of the short pentraxin CRP on microvascular endothelial cell angiogenic function. Subcutaneously implanted collagen plugs seeded with human mECs exposed to monomeric CRP (mCRP) in mice showed formation of an extended network of microvessels both in the plug and the overlying skin tissue, while mECs exposure to pentameric native CRP (nCRP) induced a much milder effect. To understand the mechanisms behind this angiogenic effects, mECs were exposed to both CRP forms and cell migration, wound repair and tube-like formation were investigated. nCRP effects were moderate and of slow-onset whereas mCRP induced rapid, and highly significant effects. We investigated how circulating nCRP is transformed into mCRP by confocal microscopy and western blot. nCRP is transformed into mCRP on the mECs membranes in a time dependent fashion. This transformation is specific and in part receptor dependent, and the formed mCRP triggers F3 gene transcription and TF-protein expression in mECs to induce angiogenesis. F3-silenced mECs are unable to form angiotubes. In agreement, mCRP induced upregulation of the TF signalling pathway in mECs with downstream phosphorylation of AKT and activation of the transcription factor ETS1 leading to increased CCL2 release. The circulating pentraxin nCRP with little pro-angiogenic effect when dissociated into mCRP on the surface of mECs is able to trigger potent proangiogenic effects by inducing F3-gene upregulation and TF signalling.

Tissue factor variants induce monocyte transformation and transdifferentiation into endothelial cell-like cells

Essentials Monocytes (Mo) transdifferentiate into endothelial cell-like (ECL) cells. Mo induce tissue factor (TF) expression and secretion in microvascular endothelial cells (mECs). TF interacts with Mo in a paracrine fashion, inducing their transdifferentiation into ECL cells. TF generates a positive feedback crosstalk between Mo and mECs that promotes angiogenesis.

SUMMARY

Background Monocytes (Mo) increase neovascularization by releasing proangiogenic mediators and/or transdifferentiating into endothelial cell-like (ECL) cells. Recently, we have reported that Mo-microvascular endothelial cells (mECs) crosstalk induces mEC-tissue factor (TF) expression and promotes angiogenesis. However, the effect of TF on Mo remains unknown. Objective Here, we analyzed whether TF might exert angiogenic effects by inducing transdifferentiation of Mo. Methods Full-length TF (flTF) and alternatively spliced TF (asTF) were overexpressed in mECs, and their supernatants were added to Mo cultures. CD16 positivity and expression of vascular endothelial cell (VEC) markers in Mo were analyzed by fluorescence activated cell sorting. The capacity to form tube-like structures were visualized in three-dimensional cultures. Results In mECs flTF and asTF expression and release were increased in cultures with Mo-conditioned media. TF variants induced expansion of a CD16+ Mo subset and Mo transdifferentiation into ECL-cells expressing VEC markers that can form new microvessels. CD16+ Mo exposed to TF showed an increased expression of VE-cadherin, von Willebrand factor (VWF) and eNOS. Mo cultured with supernatants obtained from TF-silenced mECs did not transdifferentiate to ECL-cells or expressed VEC markers. Blocking β1-integrin in Mo significantly blocked the effects of the TF variants. Conclusions Mo induce mECs to express and release TF, which drives CD16- Mo to transform into CD16+ Mo and to transdifferentiate into ECL-cells that can form new microvessels. Our results reveal a TF-mediated positive feedback between mECs and Mo that stimulates Mo differentiation and induces angiogenesis.

Stem cells from human cardiac adipose tissue depots show different gene expression and functional capacities

BACKGROUND

The composition and function of the adipose tissue covering the heart are poorly known. In this study, we have investigated the epicardial adipose tissue (EAT) covering the cardiac ventricular muscle and the EAT covering the left anterior descending artery (LAD) on the human heart, to identify their resident stem cell functional activity.

METHODS

EAT covering the cardiac ventricular muscle was isolated from the apex (avoiding areas irrigated by major vessels) of the heart (ventricular myocardium adipose tissue (VMAT)) and from the area covering the epicardial arterial sulcus of the LAD (PVAT) in human hearts excised during heart transplant surgery. Adipose stem cells (ASCs) from both adipose tissue depots were immediately isolated and phenotypically characterized by flow cytometry. The different behavior of these ASCs and their released secretome microvesicles (MVs) were investigated by molecular and cellular analysis.

RESULTS

ASCs from both VMAT (mASCs) and the PVAT (pASCs) were characterized by the expression of CD105, CD44, CD29, CD90, and CD73. The angiogenic-related genes VEGFA, COL18A1, and TF, as well as the miRNA126-3p and miRNA145-5p, were analyzed in both ASC types. Both ASCs were functionally able to form tube-like structures in three-dimensional basement membrane substrates. Interestingly, pASCs showed a higher level of expression of VEGFA and reduced level of COL18A1 than mASCs. Furthermore, MVs released by mASCs significantly induced human microvascular endothelial cell migration.

CONCLUSION

Our study indicates for the first time that the resident ASCs in human epicardial adipose tissue display a depot-specific angiogenic function. Additionally, we have demonstrated that resident stem cells are able to regulate microvascular endothelial cell function by the release of MVs.

Inhibition of cytoskeletal assembly by cytochalasin B prevents signaling through tyrosine phosphorylation and secretion triggered by collagen but not by thrombin

Activation of platelets leads to cytoskeletal assembly that is responsible for platelet motility and internal contraction. We have evaluated the involvement of the cytoskeleton in platelet activation by two strong agonists, collagen and thrombin. Activation was assessed by measuring changes in cytoskeletal assembly, externalization of activation-dependent markers and expression of procoagulant activity, and tyrosine phosphorylation of proteins, in both the absence and the presence of cytochalasin B. Activation of platelets with collagen and thrombin induced morphological changes and increased the expression of CD62P, CD63, glycoprotein IV, and binding of annexin V to platelets. Moreover, both activating agents induced actin polymerization, increased the association of other contractile proteins, and promoted tyrosine phosphorylation of multiple proteins, some of which were associated with the cytoskeleton. The presence of cytochalasin B blocked the previous events when collagen was used as the activating agent, although binding of annexin V still occurred. In contrast, platelet response to thrombin was not completely prevented by the presence of cytochalasin B. Thus, activation by collagen requires a functional cytoskeleton to trigger signaling through tyrosine phosphorylation and secretion. This is not the case for thrombin, which is capable of activating signaling mechanisms in the presence of strong inhibitors of cytoskeletal assembly. Moreover, the expression of a procoagulant surface in platelets still occurs even when platelet motility has been inhibited.

Tissue factor induces human coronary artery smooth muscle cell motility through Wnt-signalling

BACKGROUND

Tissue factor (TF) is the most relevant physiological trigger of thrombosis contributing to the presentation of clinical ischemic events after plaque rupture. However, the role of human vascular smooth muscle cell (HVSMC) TF in vascular remodeling, restenosis and atherosclerosis is less known. We have hypothesized that TF contributes to atherosclerotic lesion formation, triggering smooth muscle cell migration through a specific yet unknown signaling pathway.

OBJECTIVES

The aim of this study has been to investigate the signal transduction mechanism by which TF may contribute to the transition of resident static contractile HVSMC into a migrating cell that promotes atherosclerotic plaque progression.

METHODS

We have used a system biology discovery approach with gene-engineered HVSMCs to identify genes/proteins involved in the TF-triggered effects in HVSMC obtained from the coronary arteries of human adult hearts.

RESULTS

Analysis of wild-type HVSMC (TF(+) ) and TF(-) silenced HVSMC (TF(-) ) showed that TF is involved in the regulation of Wnt signaling and in the expression of downstream proteins that affect the atherosclerotic process.

CONCLUSIONS

The 'in silico' analysis pointed to specific Wnt-pathway proteins that have been validated in cell culture and also have been found expressed in human advanced atherosclerotic plaques but not in early lesions. TF signals through Wnt to regulate coronary smooth muscle cell migration and vascular remodeling.