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International audience; Objective: To explore the regulatory role of soluble CD146 (sCD146) and its interaction with galectin-1 (Gal1) in placenta-mediated complications of pregnancy.Design: Prospective pilot and experimental studies.Setting: University-affiliated hospital and academic research laboratory.Patient(s): One hundred fifteen women divided into three groups: 30 healthy, nonpregnant women, 50 women with normal pregnancies, and 35 with placenta-mediated pregnancy complications.Intervention(s): Wound-healing experiments were conducted to study trophoblast migration.Main outcome measure(s): Quantification of sCD146 and Gal1 by enzyme-linked immunosorbent assay. Analysis of trophoblast migration by wound closure.Result(s): Concomitant detection of sCD146 and Gal1 showed lower sCD146 and higher Gal1 concentrations in women with normal pregnancies compared with nonpregnant women. In addition, follow-up of these women revealed a decrease in sCD146 associated with an increase in Gal1 throughout pregnancy. In contrast, in women with preeclampsia, we found significantly higher sCD146 concentrations compared with women with normal pregnancies and no modification of Gal1. We emphasize the opposing effects of sCD146 and Gal, since, unlike Gal1, sCD146 inhibits trophoblast migration. Moreover, the migratory effect of Gal1 was abrogated with the use of an anti-CD146 blocking antibody or the use of small interfering RNA to silence VEGFR2 expression. This suggests that trophoblast migration is mediated though the interaction of Gal1 with CD146, further activating the VEGFR2 signaling pathway. Significantly, sCD146 blocked the migratory effects of Gal1 on trophoblasts and inhibited its secretion, suggesting that sCD146 acts as a ligand trap.Conclusion(s): Soluble CD146 could be proposed as a biomarker in preeclampsia and a potential therapeutic target. Clinical trial registration number: NCT 01736826.Trial registration: ClinicalTrials.gov NCT01736826.

Background: Triple Negative Breast Cancers (TNBC) are the most aggressive breast cancers and lead to poor prognoses. This is due to a high resistance to therapies, mainly because of the presence of Cancer Stem Cells (CSCs). Plasticity, a feature of CSCs, is acquired through the Epithelial to Mesenchymal Transition (EMT), a process that has been recently shown to be regulated by a key molecule, CD146. Of interest, CD146 is over-expressed in TNBC. Methods: The MDA-MB-231 TNBC cell line was used as a model to study the role of CD146 and its secreted soluble form (sCD146) in the development and dissemination of TNBC using in vitro and in vivo studies. Results: High expression of CD146 in a majority of MDA-MB-231 cells leads to an increased secretion of sCD146 that up-regulates the expression of EMT and CSC markers on the cells. These effects can be blocked with a specific anti-sCD146 antibody, M2J-1 mAb. M2J-1 mAb was able to reduce tumour development and dissemination in a model of cells xenografted in nude mice and an experimental model of metastasis, respectively, in part through its effects on CSC. Conclusion: We propose that M2J-1 mAb could be used as an additional therapeutic approach to fight TNBC.

International audience; Objective Systemic sclerosis (SSc) is an autoimmune disorder characterized by excessive fibrosis, immune dysfunction, and vascular damage, in which the expression of many growth factors is deregulated. CD146 was recently described as a major actor in SSc. Since CD146 also exists as a circulating soluble form (sCD146) that acts as a growth factor in numerous angiogenic- and inflammation-related pathologies, we sought to identify the mechanisms underlying the generation of sCD146 and to characterize the regulation and functions of the different variants identified in SSc. Methods We performed in vitro experiments, including RNA-Seq and antibody arrays, and in vivo experiments using animal models of bleomycin-induced SSc and hind limb ischemia. Results Multiple forms of sCD146, generated by both shedding and alternative splicing of the primary transcript, were discovered. The shed form of sCD146 was generated from the cleavage of both long and short membrane isoforms of CD146 through ADAM-10 and TACE metalloproteinases, respectively. In addition, 2 novel sCD146 splice variants, I5-13-sCD146 and I10-sCD146, were identified. Of interest, I5-13-sCD146 was significantly increased in the sera of SSc patients (P < 0.001; n = 117), in particular in patients with pulmonary fibrosis (P < 0.01; n = 112), whereas I10-sCD146 was decreased (P < 0.05; n = 117). Further experiments revealed that shed sCD146 and I10-sCD146 displayed proangiogenic activity through the focal adhesion kinase and protein kinase C epsilon signaling pathways, respectively, whereas I5-13-sCD146 displayed profibrotic effects through the Wnt-1/beta-catenin/WISP-1 pathway. Conclusion Variants of sCD146, and in particular the novel I5-13-sCD146 splice variant, could constitute novel biomarkers and/or molecular targets for the diagnosis and treatment of SSc and other angiogenesis- or fibrosis-related disorders.

Cardiac fibrosis constitutes irreversible necrosis of the heart muscle as a consequence of different acute (myocardial infarction) or chronic (diabetes, hypertension, …) diseases but also due to genetic alterations or aging. Currently, there is no curative treatment that is able to prevent or attenuate this phenomenon that leads to progressive cardiac dysfunction and life-threatening outcomes. This review summarizes the different targets identified and the new strategies proposed to fight cardiac fibrosis. Future directions, including the use of exosomes or nanoparticles, will also be discussed.

Pathologies of large vessels, such as atherosclerosis and aneurysms tend to emerge at specific sites. The consistency in their distribution suggests that a combination of unique local stressors, including both physical forces and specific gene expression profiles are confounding factors in disease etiology. Here we used single-cell RNA sequencing to identify signatures in smooth muscle cells with site-restricted predominance to uncover potentially relevant gene products. We showed that a small cohort of transcripts (5.5%) display preferential expression at specific sites of the vascular tree and in accordance with their embryological origin. Importantly, in silico studies revealed that several of these genes mapped to linkage studies for which no specific disease-causing candidates had been previously found. One of these candidates was Mcam/CD146 that mapped to the familial aortic aneurysm 1 (FAA1) locus identified by linkage analysis two decades ago. We showed that Mcam was significantly reduced in the AngII / hypercholesterolemic model of aortic aneurysm and further demonstrated that absence of the gene in mice resulted in larger lesions and accelerated death due to dissection. Our study highlighted site-specific alterations in gene expression profiles of smooth muscle cells that yield important insight in understanding site-specific vascular pathologies.

International audience; Background Platelet P2Y12 antagonist ticagrelor reduces mortality after acute myocardial infarction (AMI) compared to clopidogrel, but the underlying mechanism is unknown. Because activated platelets, leukocytes, and endothelial cells release proinflammatory and prothrombotic extracellular vesicles (EVs), we hypothesized that the release of EVs is more efficiently inhibited by ticagrelor compared to clopidogrel. Objectives We compared EV concentrations and EV procoagulant activity in plasma of patients after AMI treated with ticagrelor or clopidogrel. Methods After percutaneous coronary intervention, 60 patients with first AMI were randomized to ticagrelor or clopidogrel. Flow cytometry was used to determine concentrations of EVs from activated platelets (CD61(+), CD62p(+)), fibrinogen(+), phosphatidylserine (PS+), leukocytes (CD45(+)), endothelial cells (CD31(+), 146(+)), and erythrocytes (CD235a(+)) in plasma at randomization, after 72 hours and 6 months of treatment. A fibrin generation test was used to determine EV procoagulant activity. Results Concentrations of platelet, fibrinogen(+), PS+, leukocyte, and erythrocyte EVs increased 6 months after AMI compared to the acute phase of AMI (P = .17). Conclusions Ticagrelor attenuates the increase of EV concentrations in plasma after acute myocardial infarction compared to clopidogrel. The ongoing release of EVs despite antiplatelet therapy might explain recurrent thrombotic events after AMI and worse clinical outcomes on clopidogrel compared to ticagrelor.

Human immunodeficiency virus type 1 (HIV-1) infection promotes a generalized activation of host responses that involves not only CD4 T cells, but also cells of the microenvironment, which are not directly infected, such as endothelial cells. The mechanisms triggering HIV-1-associated vascular alterations remain poorly understood. Extracellular vesicles (EVs), implicated in cell-to-cell communication, have been recently described as carriers of microRNAs (miRNAs). Here, we show that miR-146b-5p is upregulated in both CD4 T cells, CD4 T cell-derived EVs and circulating EVs obtained from antiretroviral therapy-naive HIV-1-infected patients. We further demonstrate that EVs from T cell line overexpressing miR-146b-5p mimics (miR-146b-EVs): 1) protect their miRNA cargo from RNase degradation, 2) transfer miR-146b-5p mimics into endothelial cells and 3) reduce endothelial inflammatory responses in vitro and in vivo in the lungs of mice through the downregulation of nuclear factor-κB-responsive molecules. These data advance our understanding on chronic inflammatory responses affecting endothelial homeostasis, in infectious and non-infectious diseases and pave the way for potential new anti-inflammatory strategies.

International audience; CD146 is an endothelial junctional adhesion molecule, which expression is increased in human glomerular diseases. However, the pathological significance of this overexpression remains unknown. Induction of glomerulonephritis in mice, by using nephrotoxic serum, showed that CD146 expression was highly induced within damaged glomeruli and was associated with renal inflammation and fibrosis. Interestingly, 2 weeks after glomerulonephritis induction, CD146 knockout mice showed preserved renal function as proteinuria and blood urea nitrogen levels were significantly lower compared with wild-type littermates. Furthermore, renal structure was considerably conserved, since crescents formation, tubular dilation, monocyte and lymphocyte infiltration, and interstitial renal fibrosis were highly reduced. Colocalization with markers for different types of glomerular cells showed that CD146 expression was mainly increased within the injured endothelium of the glomerular tuft. Consequently, we generated a new transgenic strain in which CD146 was specifically deleted in the vascular endothelium. Similarly to CD146 knockout, these mice showed preservation of renal structure and function after the induction of glomerulonephritis compared with wild-type animals. These data show that endothelial CD146 plays a major role in glomerulonephritis and may represent a novel therapeutic target to reduce glomerular damage and the progression of renal disease.

International audience; Extracellular vesicles (EVs) are small vesicles released by the majority of cells in response to cell activation or death stimuli. They are grouped as small EVs or exosomes, large EVs such as microvesicles (MVs) and apoptotic bodies, resulting from distinct mechanisms of generation. EVs are released into the extracellular space, in most human biological fluids and tissues, including atherosclerotic plaques. They transport complex cargo of bioactive molecules, including proteins, lipids and genetic material and are therefore involved in pathophysiological pathways of cell-cell communication. Indeed, EVs are involved in several processes such as inflammation, coagulation, vascular dysfunction, angiogenesis and senescence, contributing to the initiation and progression of atherothrombotic diseases. Consequently, they behave as a determinant of atherosclerotic plaque vulnerability leading to major cardiovascular disorders. Over the last decade, the field of EVs research has grown, highlighting their involvement in atherosclerosis. However, limitations in both detection methodologies and standardisation have hindered implementation of EVs in the clinical settings. This review summarizes the effect of EVs in atherosclerosis development, progression and severity, with specific attention devoted to their ambivalent roles in senescence and hemostasis. This review will also highlight the role of MVs as multifaceted messengers, able to promote or to attenuate atherosclerosis progression. Finally, we will discuss the main technical challenges and prerequisites of standardization for driving EVs to the clinics and delineate their relevance as emergent biomarkers and innovative therapeutic approaches in atherosclerosis.

International audience; Background: Takayasu arteritis (TAK) is a large vessel vasculitis resulting in artery wall remodeling with segmental stenosis and/or aneurysm formation. Mast cells (MCs) are instrumental in bridging cell injury and inflammatory response.Objectives: This study sought to investigate the contribution of MCs on vessel permeability, angiogenesis, and fibrosis in patients with TAK. Methods: MC activation and their tissue expression were assessed in sera and in aorta from patients with TAK and from healthy donors (HDs). In vivo permeability was assessed using a modified Miles assay. Subconfluent cultured human umbilic vein endothelial cells and fibroblasts were used in vitro to investigate the effects of MC mediators on angiogenesis and fibrogenesis.Results: This study found increased levels of MC activation markers (histamine and indoleamine 2,3-dioxygenase) in sera of patients with TAK compared with in sera of HDs. Marked expression of MCs was shown in aortic lesions of patients with TAK compared with in those of noninflammatory aorta controls. Using Miles assay, this study showed that sera of patients with TAK significantly increased vascular permeability in vivo as compared with that of HDs. Vessel permeability was abrogated in MC-deficient mice. MCs stimulated by sera of patients with TAK supported neoangiogenesis (increased human umbilic vein endothelial cell proliferation and branches) and fibrosis by inducing increased production of fibronectin, type 1 collagen, and a-smooth muscle actin by fibroblasts as compared to MCs stimulated by sera of HD.Conclusions: MCs are a key regulator of vascular lesions in patients with TAK and may represent a new therapeutic target in large vessel vasculitis.

International audience; Initially discovered in human melanoma, CD146/MCAM is expressed on many tumors and is correlated with cancer progression and metastasis. However, targeting CD146 remains challenging since it is also expressed on other cell types, as vessel cells, where it displays important physiological functions. We previously demonstrated that CD146 is shed as a soluble form (sCD146) that vectorizes the effects of membrane CD146 on tumor angiogenesis, growth and survival. We thus generated a novel monoclonal antibody, the M2J-1 mAb, which specifically targets sCD146, but not membrane CD146, and counteracts these effects. In our study, we analyzed the effects of sCD146 on the dissemination and the associated procoagulant phenotype in two highly invasive human CD146-positive cancer cell lines (ovarian and melanoma). Results show that sCD146 induced epithelial to mesenchymal transition, favored the generation of cancer stem cells and increased the membrane expression of tissue factor. Treatment of cancer cells with sCD146 in two experimental models (subcutaneous xenografting and intracardiac injection of cancer cells in nude mice) led to increased tumor dissemination and procoagulant activity. The M2J-1 mAb drastically reduced metastasis but also procoagulant activity, in particular by decreasing the number of circulating tumor microparticles, and blocked the relevant signaling pathways as demonstrated by RNA expression profiling experiments. Thus, our findings demonstrate that sCD146 mediates important pro-metastatic and procoagulant effects in two CD146-positive tumors. Targeting sCD146 with the newly generated M2J-1 mAb could constitute an innovative strategy for preventing dissemination and thromboembolism in many CD146-positive tumors.

International audience; E dema is the main symptom of nephrotic syndrome associated to minimal change disease (MCD). Besides the increase in glomerular permeability, possibly induced by a circulating permeability factor, 1 an increase in systemic vascular permeability could participate in the constitution of edema. This study was conducted to evaluate the permeability of endothelial cells (EC) exposed to serum from nephrotic patients with MCD, to low-or high-molecularweight molecules, by trans-or paracellular transport.

International audience; Activated platelets contribute to thrombosis and inflammation by the release of extracellular vesicles (EVs) exposing P-selectin, phosphatidylserine (PS) and fibrinogen. P2Y12 receptor antagonists are routinely administered to inhibit platelet activation in patients after acute myocardial infarction (AMI), being a combined antithrombotic and anti-inflammatory therapy. The more potent P2Y12 antagonist ticagrelor improves cardiovascular outcome in patients after AMI compared to the less potent clopidogrel, suggesting that greater inhibition of platelet aggregation is associated with better prognosis. The effect of ticagrelor and clopidogrel on the release of EVs from platelets and other P2Y12-exposing cells is unknown. This study compares the effects of ticagrelor and clopidogrel on (1) the concentrations of EVs from activated platelets (primary end point), (2) the concentrations of EVs exposing fibrinogen, exposing PS, from leukocytes and from endothelial cells (secondary end points) and (3) the procoagulant activity of plasma EVs (tertiary end points) in 60 consecutive AMI patients. After the percutaneous coronary intervention, patients will be randomized to antiplatelet therapy with ticagrelor (study group) or clopidogrel (control group). Blood will be collected from patients at randomization, 48 hours after randomization and 6 months following the index hospitalization. In addition, 30 age- and gender-matched healthy volunteers will be enrolled in the study to investigate the physiological concentrations and procoagulant activity of EVs using recently standardized protocols and EV-dedicated flow cytometry. Concentrations of EVs will be determined by flow cytometry. Procoagulant activity of EVs will be determined by fibrin generation test. The compliance and response to antiplatelet therapy will be assessed by impedance aggregometry. We expect that plasma from patients treated with ticagrelor (1) contains lower concentrations of EVs from activated platelets, exposing fibrinogen, exposing PS, from leukocytes and from endothelial cells and (2) has lower procoagulant activity, when compared to patients treated with clopidogrel. Antiplatelet therapy effect on EVs may identify a new mechanism of action of ticagrelor, as well as create a basis for future studies to investigate whether lower EV concentrations are associated with improved clinical outcomes in patients treated with P2Y12 antagonists.

The mechanisms regulating inflammation in large vessels vasculitis (LVV) are poorly understood. Interleukin 33 (IL-33) has been shown to license innate and adaptive immunity by enhancing Th2 cytokines production. We aimed to examine the role of IL-33 in the immunomodulation of T cell activation in LVV. T cell homeostasis and cytokines production were determined in peripheral blood from 52 patients with giant cell arteritis (GCA) and 50 healthy donors (HD), using Luminex assay, flow cytometry, quantitative RT-PCR and by immunofluorescence analysis in inflammatory aorta lesions. We found increased level of IL-33 and its receptor ST2/IL-1R4 in the serum of patient with LVV. Endothelial cells were the main source of IL-33, whereas Th2 cells, Tregs and mast cells (MC) express ST2 in LVV vessels. IL-33 had a direct immunomodulatory impact by increasing Th2 and Tregs. IL-33 and MC further enhanced Th2 and regulatory responses by inducing a 6.1 fold increased proportion of Tregs (p = 0.008). Stimulation of MC by IL-33 increased indoleamine 2 3-dioxygenase (IDO) activity and IL-2 secretion. IL-33 mRNA expression was significantly correlated with the expression of IL-10 and TGF-β within aorta inflammatory lesions. To conclude, our findings suggest that IL-33 may exert a critical immunoregulatory role in promoting Tregs and Th2 cells in LVV.

International audience; Systemic sclerosis (SSc) is an autoimmune disorder characterized by vascular damage, excessive fibrosis and abnormal T cells immune-regulation. CD146 is an adhesion molecule essentially expressed in the vascular system, but also on TH17 lymphocytes. In view of the recently described role of CD146 in SSc, we hypothesized an involvement of CD146 positive TH17 cells in this disease. Compared to healthy controls, we showed that both soluble form of CD146 (sCD146), and IL17A levels were increased in patients with SSc with a positive correlation between both factors. A significant increase in TH17 cells attested by an increase of RORγT, IL17A mRNA and CD4+ IL17A+ cell was observed in patients with SSc. Interestingly, the percentage of TH17 cells expressing CD146 was higher in patients with SSc and inversely correlated with pulmonary fibrosis. In vitro experiments showed an augmentation of the percentage of TH17 cells expressing CD146 after cell treatment with sCD146, suggesting that, in patients the increase of this sub-population could be the consequence of the sCD146 increase in serum. In conclusion, TH17 cells expressing CD146 could represent a new component of the adaptive immune response, opening the way for the generation of new tools for the management of SSc. Systemic sclerosis (SSc) is an autoimmune disease characterized by excessive fibrosis in the skin and internal organs, vascular damage and immune dysfunction. Two major clinical subsets, namely limited cutaneous (lcSSc) and diffuse cutaneous (dcSSc) forms have been described according to the extent of skin fibrosis 1. Pulmonary fibrosis and pulmonary arterial hypertension (PAH), are the most serious complications and constitute currently the major causes of death 2,3. The study of new molecular targets is essential in the understanding of the physiopa-thology of the disease, and the establishment of new therapeutic strategies. Among them, CD146 has been recently proposed as a new molecular target in SSc 4. This cell adhesion molecule , also called MUC18 and MCAM, is a membrane glycoprotein belonging to the Immunoglobulin super family 5. It is ubiquitously distributed on endothelium 6,7 , with a preferential localization at the endothelial junction 7. CD146 is involved in several functions such as cell adhesion 8 , inflammation 9 , and angiogenesis through different signaling pathways 8. CD146 also exists as a soluble form (sCD146) in the blood, resulting from the proteolysis of the membrane form 9-11. In a mice model of SSc induced by bleomycin, we showed that mice lacking CD146 were more susceptible to develop skin fibrosis than wild type animal. Fibrosis development could be prevented by subcutaneous sCD146 injection. We also evidenced the involvement of Wnt pathway since CD146 deficiency was associated with an up-regulation of the canonical Wnt pathway, leading to the profibrotic state 4. The expression of CD146 is not restricted to the endothelium since it is also expressed on other cell types such as melanoma cells 12 , extra villous trophoblastic cells 13 and TH17 cells 14. TH17 cells are involved in the pathogenesis of several autoimmune diseases including SSc 15. These cells play a critical role in the pathogenesis of autoimmune diseases, leading to production of several cytokines as IL17A, IL22, IL21 and IL26 14. The retinoic acid receptor-related-orphan-receptor-gamma T (RORγT), is the key transcription factor required for TH17 cell

Introduction The platelet P2Y12 antagonist ticagrelor reduces all-cause and cardiovascular mortality in patients after acute myocardial infarction (AMI) compared to clopidogrel, but the underlying mechanism is unknown. Because activated platelets release prothrombotic extracellular vesicles (EVs) exposing P-selectin, fibrinogen and phosphatidylserine (PS), we hypothesized that ticagrelor inhibits the release of EVs compared to clopidogrel. Purpose To compare the effects of ticagrelor and clopidogrel on the concentrations of platelet EVs in relation to platelet reactivity, and on the concentrations of EVs from other P2Y12-exposing cells (leukocytes, endothelial cells). Methods After the percutaneous coronary intervention, patients with first AMI (n=60, age 64.5±10.8 years, 68% male) were randomized in 1:1 ratio to antiplatelet therapy with ticagrelor or clopidogrel. Venous blood was collected from fasting patients at randomisation, 48 hours after randomisation, and 6 months following the index hospitalization with informed consent. Flow cytometry (Apogee A60 Micro) was used to determine plasma concentrations of EVs labelled with antibodies for activated platelets (CD61, CD62p; PEVs), fibrinogen, phosphatidylserine (PS), leukocytes (CD45; LEVs) and endothelial cells (CD146; EEVs). To maximize the reliability, the analysis of the 1,224 flow cytometry data files was performed with software enabling automatic flow rate stabilization, diameter and refractive index determination, size distribution fitting, fluorescent gate determination, and statistics reporting (MATLAB R2018a). To differentiate between EVs and small platelets, only particles Results Concentrations of PEVs exposing P-selectin, fibrinogen and PS were lower after 6 months of therapy with ticagrelor compared to clopidogrel, and decreased over time (p=0.034; p=0.021; p=0.018, respectively). Concentrations of LEVs were lower both after 72 hours and after 6 months of therapy with ticagrelor compared to clopidogrel (p=0.018; p Conclusions Ticagrelor decreases concentrations of prothrombotic EVs, compared to clopidogrel, suggesting that the clinical benefits of ticagrelor may be at least partly explained by inhibition of EV release from activated platelets. Further research is warranted to link this effect with clinical outcomes. Acknowledgement/Funding Medical University of Warsaw (1WR/PM2/18)

International audience; Aims: The progression of atherosclerosis is based on the continued recruitment of leukocytes in the vessel wall. The previously described role of CD146 in leukocyte infiltration suggests an involvement for this adhesion molecule in the inflammatory response. In this study, we investigated the role of CD146 in leukocyte recruitment by using an experimental model of atherogenesis.Methods and results: The role of CD146 was explored in atherosclerosis by crossing CD146-/- mice with ApoE-/- mice. CD146 -/-/ApoE -/- and ApoE -/- mice were fed a Western diet for 24 weeks and were monitored for aortic wall thickness using high frequency ultrasound. The arterial wall was significantly thicker in CD146-deficient mice. After 24 weeks of Western diet, a significant increase of atheroma in both total aortic lesion and aortic sinus of CD146-null mice was observed. In addition, atherosclerotic lesions were more inflammatory since plaques from CD146-deficient mice contained more neutrophils and macrophages. This was due to up-regulation of RANTES secretion by macrophages in CD146-deficient atherosclerotic arteries. This prompted us to further address the function of CD146 in leukocyte recruitment during acute inflammation by using a second experimental model of peritonitis induced by thioglycollate. Neutrophil recruitment was significantly increased in CD146-deficient mice 12 h after peritonitis induction and associated with higher RANTES levels in the peritoneal cavity. In CD146-null macrophages, we also showed that increased RANTES production was dependent on constitutive inhibition of the p38-MAPK signaling pathway. Finally, Maraviroc, a RANTES receptor antagonist, was able to reduce atherosclerotic lesions and neutrophilia in CD146-deficient mice to the same level as that found in ApoE -/- mice.Conclusions: Our data indicate that CD146 deficiency is associated with the upregulation of RANTES production and increased inflammation of atheroma, which could influence the atherosclerotic plaque fate. Thus, these data identify CD146 agonists as potential new therapeutic candidates for atherosclerosis treatment.

International audience; Although progress was made in in vitro fertilization (IVF) techniques, the majority of embryos transferred fail to implant. Morphology embryo scoring is the standard procedure for most of IVF centres for choosing the best embryo, but remains limited since even the embryos classified as ªtop qualityº may not implant. As it has been shown that i) CD146 is involved in embryo implantation and ii) membrane form is shed to generate soluble CD146 (sCD146), we propose that sCD146 in embryo supernatants may constitute a new biomarker of embryo selection. Immunocytochemical staining showed expression of CD146 in early embryo stages and sCD146 was detected by ELISA and Western-blot in embryo supernatants from D2. We retrospectively studied 126 couples who underwent IVF attempt. The embryo culture medium from each transferred embryo (n = 222) was collected for measurement of sCD146 by ELISA. Significantly higher sCD146 concentrations were present in embryo supernatants that did not implant (n = 185) as compared to those that successfully implanted (n = 37) (1310 +/- 1152 pg.mL-1 vs. 845+/- 1173 pg.mL-1, p = 0.024). Sensitivity analysis performed on single embryo transfers (n = 71) confirmed this association (p = 0.0054). The computed ROC curve established that the optimal sCD146 concentration for embryo implantation is under 1164 pg.mL-1 (sensitivity: 76%, specificity: 48%, PPV: 25% and NPV: 92%). Over this sCD146 threshold, the implantation rate was significantly lower (9% with sCD146 levels >1164 pg.ml-1 vs. 22% with sCD146 levels 1164 pg.mL-1, p = 0.01). Among the embryos preselected by morphologic scoring, sCD146 determination could allow a better selection of the embryo(s), thus improving the success of elective single embryo transfer. This study establishes the proof of concept for the use of sCD146 as a biomarker for IVF by excluding the embryo with the highest sCD146 level. A multicentre prospective study will now be necessary to further establish its use in clinical practice.

International audience; CD146 (cluster of differentiation 146) is an adhesion molecule that is expressed by different cells constituting vessels, particularly endothelial cells. The last 30 years of research in this field have shown that CD146 plays a key role in the control of several vessel functions. Three forms of CD146 have been described, including 2 transmembrane isoforms and a soluble protein that is detectable in the plasma. These CD146 forms mediate pleiotropic functions through homophilic and heterophilic interactions with proteins present on surrounding partners. Several studies used neutralizing antibodies, siRNA, or genetically modified mice to demonstrate the involvement of CD146 in the regulation of angiogenesis, vascular permeability, and leukocyte transmigration. In this review, we will focus on the current knowledge of the roles of CD146 in vascular homeostasis and diseases associated with endothelial dysfunction.

Cell-based therapies constitute a real hope for the treatment of ischaemic diseases. One of the sources of endothelial progenitors for autologous cell therapy is Endothelial Colony Forming Cells (ECFC) that can be isolated from peripheral blood. However, their use is limited by their low number in the bloodstream and the loss of their stem cell phenotype associated with the acquisition of a senescent phenotype in culture. We hypothesized that adding soluble CD146, a novel endothelial growth factor with angiogenic properties, during the isolation and growth procedures could improve their number and therapeutic potential. Soluble CD146 increased the number of isolated peripheral blood ECFC colonies and lowered their onset time. It prevented cellular senescence, induced a partial mesenchymal phenotype and maintained a stem cell phenotype by stimulating the expression of embryonic transcription factors. These different effects were mediated through the induction of mature miR-21. When injected in an animal model of hindlimb ischaemia, sCD146-primed ECFC isolated from 40 ml of blood from patients with peripheral arterial disease were able to generate new blood vessels and restore blood flow. Treatment with sCD146 could thus constitute a promising strategy to improve the use of autologous cells for the treatment of ischaemic diseases.

Background Mammalian target of rapamycin complex 1 (mTORC 1) drives the proinflammatory expansion of T helper (TH) type 1, TH17 cells and controls fibroblast proliferation, typical features of large vessel vasculitis (LVV) pathogenesis. Molecular pathways involved in arterial lesions of LVV are unknown. Objectives To analyse mTOR pathway activation in LVV (giant cell arteritis and Takayasu arteritis). Methods We evaluate pathway activation in the mTORC and the nature of cell proliferation in blood and vessels of patients with LVV compared non-inflammatory aorta by using double immunostaining, western blot and flow cytometry. Finally, using flow cytometry, we study the effect of rapamycin on T cells homeostasis in LVV compared to HD. Results Proliferation of both endothelial cells and vascular smooth-muscle cells was shown in vascular lesions in LVV. The vascular endothelium of proliferating aorta vessels from patients with LVV showed indications of activation of the mTORC1 pathway en endothelial cells (S6RP phosphorylation) compared to non-inflammatory aorta (45%24;48 versus 10.4% [9.7;14.9] positive S6RP endothelial cells, p=0.03). In cultured vascular endothelial cells, sera from patients with LVV stimulated mTORC1 through the phosphorylation of S6RP. Activation of mTORC1 was also found in Th1 and Th17 cells both systemically and in the blood vessels. Patients with LVV exhibited a diminished S6RP phosphorylation in Tregs. Inhibition of mTORC1 pathway with rapamycin, increase Tregs and decrease effector CD4+IFNγ+, CD4+IL17+ and CD4+IL21+ T cells in patients with LVV. Conclusions Our results suggest that the mTORC1 pathway is involved in the vascular lesions of LVV. Targeting mTORC pathway may represent a new therapeutic option in patients with LVV. Disclosure of Interest None declared

International audience; We highlight for the first time that CD146/sCD146 is involved in fibrotic process during SSc. sCD146 could thus constitute a new biomarker to assess disease activity, and potentially a new target for therapeutic applications.

CD146 is an adhesion molecule present on many tumors (melanoma, kidney, pancreas, breast, ...). In addition, it has been shown to be expressed on vascular endothelial and smooth muscle cells. Generating an antibody able to specifically recognize CD146 in cancer cells (designated as tumor CD146), but not in normal cells, would thus be of major interest for targeting tumor CD146 without affecting the vascular system. We thus generated antibodies against the extracellular domain of the molecule produced in cancer cells and selected an antibody that specifically recognizes tumor CD146. This antibody (TsCD146 mAb) was able to detect CD146-positive tumors in human biopsies and in vivo, by PET imaging, in a murine xenograft model. In addition, TsCD146 mAb antibody was able to specifically detect CD146-positive cancer microparticles in the plasma of patients. TsCD146 mAb displayed also therapeutic effects since it was able to reduce the growth of human CD146-positive cancer cells xenografted in nude mice. This effect was due to a decrease in the proliferation and an increase in the apoptosis of CD146-positive cancer cells after TsCD146-mediated internalization of the cell surface CD146. Thus, TsCD146 mAb could be of major interest for diagnostic and therapeutic strategies against CD146-positive tumors in a context of personalized medicine.

CD146 is an adhesion molecule expressed by both melanoma and endothelial cells and thus is well positioned to control melanoma extravasation. Nevertheless, during melanoma metastasis, the involvement of CD146 expressed within tumor microenvironment has never been analyzed. To investigate whether host CD146 mediates the extravasation of melanoma cells across the endothelium, we generated CD146 KO mice. We demonstrated that host CD146 did not affect melanoma growth or tumor angiogenesis but promoted hematogenous melanoma metastasis to the lung. Accordingly, the survival of CD146-deficient mice was markedly prolonged during melanoma metastasis. Interestingly, vascular endothelial growth factor-induced vascular permeability was significantly decreased in CD146 KO mice. We also provided evidence that VEGF-induced transendothelial migration of melanoma cells was significantly reduced across CD146 KO lung microvascular endothelial cells (LMEC). CD146 deficiency decreased the expression of VEGFR-2/Ve-cadherin and altered focal adhesion kinase (FAK) activation in response to VEGF. In addition, inhibition of FAK phosphorylation reduced transmigration of B16 melanoma cells across WT LMEC at the same level that across CD146 KO LMEC. Altogether, we propose a novel mechanism involving the VEGF/CD146/FAK/Ve-cadherin network in melanoma extravasation across the vessel barrier that identifies CD146-targeted therapy as a potential strategy for the treatment of melanoma metastasis.

Introduction Les patients presentant un syndrome nephrotique a Lesions glomerulaires Minimes (SNLGM) developpent des œdemes, de mecanisme complexe, qui pourrait reposer en partie sur une augmentation de la permeabilite vasculaire peripherique. Methodes L’objectif de ce travail etait d’evaluer la permeabilite des cellules endotheliales (CE) exposees au serum des patients SNLGM et les mecanismes impliques. Le serum des patients SNLGM etait preleve au moment de la biopsie renale. Les comparaisons etaient realisees avec du serum de volontaires sains (VS) apparies. In vitro, les CE (HUVEC) ont ete exposees au serum pour mesurer : l’impedance de la monocouche confluente d’HUVEC ; la transmigration endotheliale des molecules de haut poids moleculaire (FITC) ou du sodium (Na fluorescein) ; la quantite des proteines d’interet mesuree par Western Blot. In vivo, la permeabilite vasculaire a ete mesuree chez des souris sauvages C57BL/6 J par un test au bleu Evans (Miles Assay). Resultats obtenus ou attendus Le serum SNLGM induit une augmentation de la permeabilite des HUVEC mesuree par impedance (p = 0,0276). La permeabilite des HUVEC au sodium (NaF) est augmentee en presence de serum SNLGM (p = 0,0286), mais pas la permeabilite au FITC. La permeabilite paracellulaire, evaluee in vitro par le ratio VE-cadherine phosphorylee/totale, et in vivo par le test au bleu Evans, n’est pas modifiee. Le serum SNLGM induit une augmentation de permeabilite transcellulaire non dependante de la Caveoline 1 (siRNA de Caveoline 1). L’augmentation de la permeabilite au NaF induite par le serum SNLGM est inhibee en presence d’Amiloride, un inhibiteur d’ENaC ( Fig. 1 , p = 0,0499). Conclusion Le serum SNLGM induit une augmentation de la permeabilite endotheliale au sodium, participant probablement a la constitution des œdemes. Cet effet est inhibe par l’Amiloride, un inhibiteur d’ENaC. Cette etude suggere l’existence d’un facteur de permeabilite vasculaire systemique au cours du SNLGM, impliquant une activation endotheliale d’ENaC.

ObjectivesThis study sought to analyze whether the plasmatic level of leukocyte-derived microparticles (LMP) is associated with unstable plaques in patients with high-grade carotid stenosis.BackgroundPreventive carotid surgery in asymptomatic patients is currently debated given the improvement of medical therapy. Therefore, noninvasive biomarkers that can predict plaque instability are needed. The LMPs, originating from activated or apoptotic leukocytes, are the major microparticle (MP) subset in human carotid plaque extracts.MethodsForty-two patients with >70% carotid stenosis were enrolled. Using a new standardized high-sensitivity flow cytometry assay, LMPs were measured before thromboendarterectomy. The removed plaques were characterized as stable or unstable using histological analysis according to the American Heart Association criteria. The LMP levels were analyzed according to the plaque morphology.ResultsThe median LMP levels were significantly higher in patients with unstable plaque (n = 28; CD11bCD66b+ MP/μl 240 [25th to 75th percentile: 147 to 394], and CD15+ MP/μl 147 [60 to 335]) compared to patients with stable plaque (16 [0 to 234] and 55 [36 to 157]; p < 0.001 and p < 0.01, respectively). The increase in LMP levels was also significant when considering only the group of asymptomatic patients with unstable plaque (n = 10; CD11bCD66b+ MP/μl 199 [153 to 410] and CD15+ MP/μl 78 [56 to 258] compared with patients with stable plaque (n = 14; 20 [0 to 251] and 55 [34 to 102]; p < 0.05 and p < 0.05, respectively). After logistic regression, the neurologic symptoms (odds ratio: 48.7, 95% confidence interval: 3.0 to 788, p < 0.01) and the level of CD11bCD66b+ MPs (odds ratio: 24.4, 95% confidence interval: 2.4 to 245, p < 0.01) independently predicted plaque instability.ConclusionsLMP constitute a promising biomarker associated with plaque vulnerability in patients with high-grade carotid stenosis. These data provide clues for identifying asymptomatic subjects that are most at risk of neurologic events.

Summary. Microparticles (MPs) represent a heterogeneouspopulation of submicronic vesicles that are released inresponse to cell activation or apoptosis. MPs harbor alarge repertoire of cell surface receptors and mRNA andbiological activities representative of their parent cells andrelated to their involvement in many biological functions.Although MP generation is a physiological response, adramatic increase in circulating MPs is detectable in a vari-ety of thrombosis-associated disorders compared withhealthy individuals. In this review, we will discuss a newvision of MPs as complex and ambivalent structures thatexpress both activators and inhibitors of coagulation butalso convey fibrinolytic properties. After summarizingour current knowledge about the role of MPs in venousand arterial thrombosis, this review will explore how thisnew vision of MPs influences their definition as emergentbiomarkers in thrombotic diseases. Among the studiesthat have aimed to establish a link between thrombosisand MPs, a few studies have demonstrated a predictivevalue of MPs. So far, it is unclear whether this limitedcausative association is the result of current technicalconcerns and limited standardization or has to be inte-grated into a more complex vision of the role of MPs askey systems for regulating the balance between coagula-tion and fibrinolysis.Keywords: biomarker, cell-derived microparticles, coagu-lation, fibrinolysis, risk, thrombosis.IntroductionDespite the progress that has been achieved in the treat-ment of cardiovascular diseases (CVDs), thrombosisremains a major cause of mortality and morbidity indeveloped countries [1]. Although treatment for tradi-tional cardiovascular risk factors plays a pivotal role inprimary and secondary prevention, epidemiological stud-ies indicate that adequate treatment of these risk factorsdoes not eliminate the risk of CVD, as the incidence ofrisk factors is increasing all over the world [2]. Therefore,identifying new biomarkers and potential therapeutic tar-gets is crucial. Evidence in the literature from the last20 years indicates that cell-derived microparticles (MPs)behave as bioactive agents with a key role in regulatingvascular homeostasis and the mechanisms that triggerthrombus formation [3,4]. Therefore, MPs can be consid-ered as potential biomarkers and therapeutic targets thatmay provide new approaches to fight against arterial andvenous thrombotic diseases.Among microvesicles, MPs are small vesicles that resultfrom the blebbing of the cellular membrane during activa-tion or apoptosis processes. They are commonly describedas heterogeneous vesicles with a diameter of 100–1000 nmand generally express antigens representative of their par-ent cells [5]. Presence of phosphatidylserine (PS) has longbeen a major criterion of the MP definition but is nowdebated in the literature [6]. These characteristics distin-guish MPs from exosomes, which are vesicles with adiameter of < 100 nm that are stored intracellularly inmultivesicular bodies [7], and from apoptotic bodies cor-responding to larger cell fragments, which result from thelate stages of apoptosis [8].The first-described property of cell-derived MPs hasbeen their procoagulant potential, mainly based on PSexposure and tissue factor (TF) expression [9]. This char-acteristic is the reason MPs were ascribed important rolesin coagulation activation, arterial and venous thrombosis,and CVD [10]. Furthermore, the current concept is thatMPs modulate other functions such as inflammation,angiogenesis, or immune responses and are involved indynamic interactions with target cells. MPs are, therefore,considered to be key actors in cell communication [11].More recently, the possible deleterious role of MPs hasbeen challenged by the identification of MPs that drive

CD146 is a highly glycosylated junctional adhesion molecule, expressed on human vascular endothelial cells and involved in the control of vessel integrity. Galectin-1 is a lectin produced by vascular cells that can binds N- and O-linked oligosaccharides of cell membrane glycoproteins. Because both CD146 and Galectin-1 are involved in modulation of cell apoptosis, we hypothesized that Galectin-1 could interact with CD146, leading to functional consequences in endothelial cell apoptosis. We first characterized CD146 glycosylations and showed that it is mainly composed of N-glycans able to establish interactions with Galectin-1. We demonstrated a sugar-dependent binding of recombinant CD146 to Galectin-1 using both ELISA and Biacore assays. This interaction is direct, with a K(D) of 3.10(-7) M, and specific as CD146 binds to Galectin-1 and not to Galectin-2. Moreover, co-immunoprecipitation experiments showed that Galectin-1 interacts with endogenous CD146 that is highly expressed by HUVEC. We observed a Galectin-1-induced HUVEC apoptosis in a dose-dependent manner as demonstrated by Annexin-V/7AAD staining. Interestingly, both down-regulation of CD146 cell surface expression using siRNA and antibody-mediated blockade of CD146 increase this apoptosis. Altogether, our results identify Galectin-1 as a novel ligand for CD146 and this interaction protects, in vitro, endothelial cells against apoptosis induced by Galectin-1.

International audience; CD146 (MUC-18, MCAM) expression on cancer cells correlates with cancer progression and a bad prognosis in several tumors, including melanoma and pancreatic tumors. Deciphering the mechanism mediating the CD146 role in cancer is essential for generating new therapeutic strategies. We found that CD146 expression in cancer cells is associated with a secretion of soluble CD146 (sCD146) that constitutes an active player in tumor development. Indeed, sCD146 induces the overexpression of its binding protein, angiomotin, on both endothelial and cancer cells and promotes both paracrine effects on angiogenesis and autocrine effects on cancer cells proliferation and survival. These last effects are mediated in part through the induction and phosphorylation of c-myc in cancer cells. In mice models xenografted with human CD146-positive melanoma or pancreatic cancer cells, administration of a novel monoclonal antibody specifically targeting sCD146, but not its membrane form, successfully suppresses tumor vascularization and growth. Our findings demonstrate that sCD146 secreted by CD146-positive tumors mediates important pro-angiogenic and pro-tumoral effects. Targeting sCD146 with a novel neutralizing antibody could thus constitute an innovative therapeutic strategy for the treatment of CD146-positive tumors.

International audience; Aims: Endothelial colony-forming cells (ECFC) constitute an endothelial progenitor fraction with a promising interest for the treatment of ischaemic cardiovascular diseases. As soluble CD146 (sCD146) is a new factor promoting angiogenesis, we examined whether sCD146 priming could improve the therapeutic potential of ECFC and defined the involved mechanism.Methods and results: We investigated the effects of sCD146 priming on regenerative properties of ECFC in vivo. In a mouse model of hindlimb ischaemia, the homing of radiolabelled cells to ischaemic tissue was assessed by SPECT-CT imaging. Soluble CD146 priming did not modify the number of engrafted ECFC but improved their survival capacity, leading to an enhanced revascularization. The mechanism of action of sCD146 on ECFC was studied in vitro. We showed that sCD146 acts in ECFC through a signalosome, located in lipid rafts, containing angiomotin, the short isoform of CD146 (shCD146), VEGFR1, VEGFR2, and presenilin-1. Soluble CD146 induced a sequential proteolytic cleavage of shCD146, with an extracellular shedding followed by an intramembrane cleavage mediated by matrix metalloprotease (MMP)/ADAM and presenilin-1, respectively. The generated intracellular part of shCD146 was directed towards the nucleus where it associated with the transcription factor CSL and modulated the transcription of genes involved in cell survival (FADD, Bcl-xl) and angiogenesis (eNOS). This effect was dependent on both VEGFR1 and VEGFR2, which were rapidly phosphorylated by sCD146.Conclusions: These findings establish that activation of the proteolytic processing of shCD146, in particular by sCD146, constitutes a promising pathway to improve endothelial progenitors' regenerative properties for the treatment of cardiovascular diseases.

Rationale: The progression of atherosclerosis is based on the continued recruitment of leukocytes in the vessel wall. The previously described role of CD146 in leukocyte infiltration in vitro suggests a role for this endothelial junction molecule in the pathogenesis of atherosclerosis. However, its involvement in atherosclerotic plaques formation has never been investigated. Objective: We evaluated the role of CD146 in atherogenesis. Methods and Results: CD146 -/-/ApoE -/- and ApoE -/- mice were fed a Western diet for 24 weeks and were monitored for aortic wall thickness using high frequency ultrasound. The arterial wall thickness was significantly higher in CD146 deficient mice. We evidenced a significant increase of atheroma in both total aortic lesion and aortic sinus of CD146 deficient mice. In addition, atherosclerotic lesions were more inflammatory since CD146 deficient plaques contained more neutrophils and more macrophages. During atherosclerosis, circulating neutrophils were significantly increased in the absence of CD146. Consistent with the higher recruitment of inflammatory cells to the atheroma, we demonstrated that RANTES was up-regulated in CD146 deficient atherosclerotic arteries. In addition, CD146 deficient mice presented significant higher levels of circulating RANTES during atherosclerosis. Finally, we showed that macrophages were the source of RANTES and its production by CD146 null macrophages was also significantly increased through a mechanism dependent of p38-MAPK signaling pathway. Conclusions: Our data indicate that CD146 deficiency is associated with the upregulation of RANTES and increased inflammation of atheroma, which could influence the atherosclerotic plaque fate. Thus, these data identify CD146 as a potential new target for atherosclerosis treatment.

International audience; BACKGROUND: We recently assigned a new fibrinolytic function to cell-derived microparticles in vitro. In this study we explored the relevance of this novel property of microparticles to the in vivo situation. DESIGN AND METHODS: Circulating microparticles were isolated from the plasma of patients with thrombotic thrombocytopenic purpura or cardiovascular disease and from healthy subjects. Microparticles were also obtained from purified human blood cell subpopulations. The plasminogen activators on microparticles were identified by flow cytometry and enzyme-linked immunosorbent assays; their capacity to generate plasmin was quantified with a chromogenic assay and their fibrinolytic activity was determined by zymography. RESULTS: Circulating microparticles isolated from patients generate a range of plasmin activity at their surface. This property was related to a variable content of urokinase-type plasminogen activator and/or tissue plasminogen activator. Using distinct microparticle subpopulations, we demonstrated that plasmin is generated on endothelial and leukocyte microparticles, but not on microparticles of platelet or erythrocyte origin. Leukocyte-derived microparticles bear urokinase-type plasminogen activator and its receptor whereas endothelial microparticles carry tissue plasminogen activator and tissue plasminogen activator/inhibitor complexes. CONCLUSIONS: Endothelial and leukocyte microparticles, bearing respectively tissue plasminogen activator or urokinase-type plasminogen activator, support a part of the fibrinolytic activity in the circulation which is modulated in pathological settings. Awareness of this blood-borne fibrinolytic activity conveyed by microparticles provides a more comprehensive view of the role of microparticles in the hemostatic equilibrium.

Cell-derived microparticles are complex vesicular structures that can be shedded by activated or apoptotic endothelial cells. Cell-derived microparticles are composed of a phospholipid bilayer that exposes transmembrane proteins and receptors and encloses cytosolic components such as enzymes, transcription factors and mRNA derived from their parent cells. Thus, they behave as biological conveyors playing a key role in the tuning of vascular homeostasis. This review will address the potential of microparticles as efficient vectors of biological activities in pathologies. Based on the model of endothelial vesiculation, the first part of this review will develop the contribution of endothelial microparticles to coagulation inflammation and angiogenesis and their role in vascular disorders. The second part will be focused on the multifaceted impact of cell-derived microparticles present in blood products and its relevance to transfusion medicine.

SummaryEndothelial microparticles (EMP) are complex vesicular structures that can be shed by activated or apoptotic endothelial cells. EMP are composed of a phospholipid bilayer that exposes transmembrane proteins and receptors and encloses cytosolic components such as enzymes, transcription factors and mRNA derived from their parent cells. Thus, EMP behave as biological conveyors playing a key role in the tuning of vascular homeostasis. This review focuses on the multifaceted roles of EMP, notably in coagulation, inflammation and angiogenesis and also on the mechanisms that trigger their formation. In this context, EMP could compromise vascular homeostasis and then represent key players in the pathogenesis of several inflammatory and thrombotic diseases. Consequently, elucidating their role and their mechanisms of formation will bring new insights into the understanding of endothelial-associated diseases. Moreover, in the future, it can open novel therapeutic perspectives based on the inhibition of EMP release.

OBJECTIVE Diabetic retinopathy is associated with progressive retinal capillary activation and proliferation, leading to vision impairment and blindness. Microparticles are submicron membrane vesicles with biological activities, released following cell activation or apoptosis. We tested the hypothesis that proangiogenic microparticles accumulate in vitreous fluid in diabetic retinopathy. RESEARCH DESIGN AND METHODS Levels and cellular origin of vitreous and plasma microparticles from control (n = 26) and diabetic (n = 104) patients were analyzed by flow cytometry, and their proangiogenic activity was assessed by in vitro thymidine incorporation and neovessel formation in subcutaneous Matrigel plugs in mice. RESULTS Microparticles of endothelial, platelet, photoreceptor, and microglial origin were identified in vitreous samples. Levels of photoreceptor and microglial microparticles were undetectable in plasmas but were comparable in diabetic and control vitreous samples. Vitreous platelet and endothelial microparticles levels were increased in diabetic patients and decreased following panretinal laser photocoagulation or intravitreal antivascular endothelial growth factor injection in proliferative diabetic retinopathy (PDR). The ratio of vitreous to plasma microparticle levels was calculated to estimate local formation versus potential plasma leakage. In PDR, the endothelial microparticles ratio—but not that for platelet—was greater than 1.0, indicating local formation of endothelial microparticles from retinal vessels and permeation of platelet microparticles from plasma. Isolated vitreous microparticles stimulated by 1.6-fold endothelial proliferation and increased new vessel formation in mice. CONCLUSIONS The present study demonstrates that vitreous fluid contains shed membrane microparticles of endothelial, platelet, and retinal origin. Vitreous microparticles levels are increased in patients with diabetic retinopathy, where they could contribute to disease progression.

Cell activation or apoptosis leads to plasma membrane blebbing and microparticles (MPs) release. MPs are submicron membrane vesicles expressing a panel of oxidized phospholipids and proteins specific of the cells they originate from. Exposure of negatively charged phospholipids and tissue factor confers a procoagulant potential to MPs. Increases in plasma MPs levels, particularly those of endothelial origin, reflects cellular injury and appears now as a surrogate marker of vascular dysfunction. MPs are also biologically active and stimulate pro-inflammatory responses in target cells. Thus, MPs can promote a prothrombogenic and pro-inflammatory vicious circle leading to vascular dysfunction. A better understanding of MPs composition, as well as their effects and the mechanisms leading to their clearance will likely open new therapeutic approaches in the treatment and the prognosis of cardiovascular diseases.

Aims We analysed the possible protective role of human endothelial (EPCs) and smooth muscle (SPCs) progenitor cells on atherosclerosis development in apoE−/−RAG2−/− mice. We determined plasma levels of SPCs in coronary patients. Methods and results ApoE−/−RAG2−/− mice received four intravenous injections of saline, 5 × 105 SPCs, or 5 × 105 EPCs every other week, one (preventive approach) or 12(curative approach) weeks after starting a high fat diet. Derived-SPC levels were quantified from blood mononuclear cells of patients with stable angina ( n = 10) and acute coronary syndromes (ACS, n = 9). SPCs reduced atherosclerosis development by 42% ( P < 0.001), but had no effect on lesion progression. In the SPC group, collagen and smooth muscle cell content were increased (+80%, P < 0.001, +46%, P < 0.05, respectively), and macrophage content was decreased (−41%, P < 0.05). In the curative approach, macrophage content decreased by 40.5% ( P < 0.05) after SPC injection. EPC injection had no effect on atherosclerosis development or progression. Peripheral blood-derived SPC levels were reduced in patients with ACS compared with stable angina patients ( P < 0.05). Conclusion We demonstrate that SPCs limit plaque development and promote changes in plaque composition towards a stable phenotype in mice. Our finding in patients suggests that reduced peripheral blood-derived SPC levels might represent a mechanism contributing to plaque destabilization.

Human atherosclerotic plaques express the metalloprotease tumor necrosis factor (TNF)-alpha converting enzyme (TACE/ADAM-17), which cleaves several transmembrane proteins including TNF and its receptors (TNFR-1 and TNFR-2). Plaques also harbor submicron vesicles (microparticles, MPs) released from plasma membranes after cell activation or apoptosis. We sought to examine whether TACE/ADAM17 is present on human plaque MPs and whether these MPs would affect TNF and TNFR-1 cellular shedding. Flow cytometry analysis detected 12,867 +/- 2007 TACE/ADAM17(+) MPs/mg of plaques isolated from 25 patients undergoing endarterectomy but none in healthy human internal mammary arteries. Plaque MPs harbored mainly mature active TACE/ADAM17 and dose dependently cleaved a pro-TNF mimetic peptide, whereas a preferential TACE/ADAM17 inhibitor (TMI-2) and recombinant TIMP-3 prevented this cleavage. Plaque MPs increased TNF shedding from the human cell line ECV-304 overexpressing TNF (ECV-304(TNF)), as well as TNFR-1 shedding from activated human umbilical vein endothelial cells or ECV-304(TNF) cells, without affecting TNF or TNFR-1 synthesis. MPs also activated the shedding of the endothelial protein C receptor from human umbilical vein endothelial cells. All these effects were inhibited by TMI-2. The present study shows that human plaque MPs carry catalytically active TACE/ADAM17 and significantly enhance the cell surface processing of the TACE/ADAM17 substrates TNF, TNFR-1, and endothelial protein C receptor, suggesting that TACE/ADAM17(+) MPs could regulate the inflammatory balance in the culprit lesion.

Endothelial dysfunction and arterial stiffness are major determinants of cardiovascular risk in patients with end-stage renal failure (ESRF). Microparticles are membrane fragments shed from damaged or activated cells. Because microparticles can affect endothelial cells, this study investigated the relationship between circulating microparticles and arterial dysfunction in patients with ESRF and identified the cellular origin of microparticles associated with these alterations. Flow cytometry analysis of platelet-free plasma from 44 patients with ESRF indicated that circulating levels of Annexin V+ microparticles were increased compared with 32 healthy subjects, as were levels of microparticles derived from endothelial cells (three-fold), platelets (16.5-fold), and erythrocytes (1.6-fold). However, when arterial function was evaluated noninvasively in patients with ESRF, only endothelial microparticle levels correlated highly with loss of flow-mediated dilation (r = -0.543; P = 0.004), increased aortic pulse wave velocity (r = 0.642, P0.0001), and increased common carotid artery augmentation index (r = 0.463, P = 0.0017), whereas platelet-derived, erythrocyte-derived, and Annexin V+ microparticle levels did not. In vitro, microparticles from patients with ESRF impaired endothelium-dependent relaxations and cyclic guanosine monophosphate generation, whereas microparticles from healthy subjects did not. Moreover, in vitro endothelial dysfunction correlated with endothelial-derived (r = 0.891; P = 0.003) but not platelet-derived microparticle concentrations. In fact, endothelial microparticles alone decreased endothelial nitric oxide release by 59 +/- 7% (P = 0.025). This study suggests that circulating microparticles of endothelial origin are tightly associated with endothelial dysfunction and arterial dysfunction in ESRF.

Introduction Les vascularites des gros vaisseaux comprennent principalement la maladie de Takayasu (TA) et l’arterite a cellules geantes (AGC). Elles sont caracterisees par des reponses Th1 et Th17 predominantes. Objectifs Evaluer le role de l’IL-33 et des mastocytes sur la regulation de la reponse immune dans les vascularites des gros vaisseaux. Patients et methodes Nous avons inclus 54 patients ayant une maladie de Takayasu, 52 patients ayant une arterite a cellules geantes et 50 temoins sains. Nous avons evalue la production de cytokines et la proportion de lymphocytes T regulateurs (Treg), par cytometrie en flux et Luminex®, dans les cultures de cellules mononucleees peripheriques (PBMC) de patients ayant une vascularite des gros vaisseaux, stimulees ou non par l’IL-33 ainsi que dans les co-cultures de lymphocytes T CD4+ de patients et de mastocytes (en presence ou non d’IL-33). Resultats Nous avons mis en evidence des taux augmentes d’IL-33 dans le serum et au niveau aortique chez les patients ayant une vascularite des gros vaisseaux par rapport aux temoins. La proportion de mastocytes etait egalement augmentee dans les aortes de patients ayant une vascularite des gros vaisseaux par rapport aux aortes controles non inflammatoires. La presence d’IL-33 s’accompagnait d’une augmentation significative de l’expression de cytokines Th2 par les PBMC de patients. Les mastocytes stimules par IL-33 induisaient une augmentation encore plus importante de secretion de cytokines Th2. L’IL-33 etait egalement associee a une augmentation significative de la proportion de Treg. L’IL-33, en presence de mastocytes, induisait une augmentation encore plus importante de la proportion de Treg [proportion mediane des lymphocytes T CD25hiFOXP3+ CD4+ de 1,88 % au sein des lymphocytes T CD4+ seuls vs 11,02 % dans les lymphocytes T CD4+ en presence de mastocytes et d’IL-33 (p = 0,008)]. Les mastocytes stimules par l’IL-33 etaient egalement associes a une augmentation d’indoleamine-2 3-dioxygenase (IDO) et d’IL-2. In vivo, l’expression relative des ARNm de l’IL-33 etait significativement correlee a celles de l’IL-10 et du TGF-β au sein des lesions inflammatoires aortiques. Conclusion L’axe IL-33/ST2, grâce a son interaction avec les mastocytes, a une action immunoregulatrice dans les vascularites des gros vaisseaux.

CD146 is an adhesion molecule expressed by both melanoma and endothelial cells and thus is well positioned to control melanoma extravasation. Nevertheless, during melanoma metastasis, the involvement of CD146 expressed within tumor microenvironment has never been analyzed. To investigate whether host CD146 mediates the extravasation of melanoma cells across the endothelium, we generated CD146 KO mice. We demonstrated that host CD146 did not affect melanoma growth or tumor angiogenesis but promoted hematogenous melanoma metastasis to the lung. Accordingly, the survival of CD146-deficient mice was markedly prolonged during melanoma metastasis. Interestingly, vascular endothelial growth factor-induced vascular permeability was significantly decreased in CD146 KO mice. We also provided evidence that VEGF-induced transendothelial migration of melanoma cells was significantly reduced across CD146 KO lung microvascular endothelial cells (LMEC). CD146 deficiency decreased the expression of VEGFR-2/Ve-cadherin and altered focal adhesion kinase (FAK) activation in response to VEGF. In addition, inhibition of FAK phosphorylation reduced transmigration of B16 melanoma cells across WT LMEC at the same level that across CD146 KO LMEC. Altogether, we propose a novel mechanism involving the VEGF/CD146/FAK/Ve-cadherin network in melanoma extravasation across the vessel barrier that identifies CD146-targeted therapy as a potential strategy for the treatment of melanoma metastasis.

Rationale and Objective: Membrane-shed submicron microparticles (MPs) released following cell activation or apoptosis accumulate in atherosclerotic plaques, where they stimulate endothelial proliferation and neovessel formation. The aim of the study was to assess whether or not MPs isolated from human atherosclerotic plaques contribute to increased endothelial adhesion molecules expression and monocyte recruitment. Method and Results: Human umbilical vein and coronary artery endothelial cells were exposed to MPs isolated from endarterectomy specimens (n=62) and characterized by externalized phosphatidylserine. Endothelial exposure to plaque, but not circulating, MPs increased ICAM-1 levels in a concentration-dependant manner (3.4-fold increase) without affecting ICAM-1 mRNA levels. Plaque MPs harbored ICAM-1 and transferred this adhesion molecule to endothelial cell membrane in a phosphatidylserine-dependent manner. MP-borne ICAM-1 was functionally integrated into cell membrane as demonstrated by the increased ERK1/2 phosphorylation following ICAM-1 ligation. Plaque MPs stimulated endothelial monocyte adhesion both in culture and in isolated perfused mouse carotid. This effect was also observed under flow condition and was prevented by anti–LFA-1 and anti–ICAM-1 neutralizing antibodies. MPs isolated from symptomatic plaques were more potent in stimulating monocyte adhesion than MPs from asymptomatic patients. Plaque MPs did not affect the release of interleukin-6, interleukin-8, or MCP-1, nor the expression of VCAM-1 and E-selectin. Conclusion: These results demonstrate that MPs isolated from human atherosclerotic plaques transfer ICAM-1 to endothelial cells to recruit inflammatory cells and suggest that plaque MPs promote atherosclerotic plaque progression.

International audience; BACKGROUND: Atherosclerosis and non-alcoholic fatty liver disease (NAFLD) are complex pathologies characterized by lipid accumulation, chronic inflammation and extensive tissue remodelling. Microparticles (MPs), small membrane vesicles produced by activated and apoptotic cells, might not only be biomarkers, but also functional actors in these pathologies. The apoE2-KI mouse is a model of atherosclerosis and NAFLD. Activation of the nuclear receptor PPARα decreases atherosclerosis and components of non-alcoholic steatohepatitis (NASH) in the apoE2-KI mouse. OBJECTIVES: (1) To determine whether MPs are present in atherosclerotic lesions, liver and plasma during atherosclerosis and NASH progression in apoE2-KI mice, and (2) to study whether PPARα activation modulates MP concentrations. METHODS: ApoE2-KI mice were fed a Western diet to induce atherosclerosis and NASH. MPs were isolated from atherosclerotic lesions, liver and blood and quantified by flow cytometry. RESULTS: An increase of MPs was observed in the atherosclerotic lesions and in the liver of apoE2-KI mice upon Western diet feeding. PPARα activation with fenofibrate decreased MP levels in the atherosclerotic lesions in a PPARα-dependent manner, but did not influence MP concentrations in the liver. CONCLUSION: Here we report that MPs are present in atherosclerotic lesions and in the liver of apoE2-KI mice. Their concentration increased during atherosclerosis and NASH development. PPARα activation differentially modulates MP levels in a tissue-specific manner.

Background— We hypothesized that microparticles (MPs) released after ischemia are endogenous signals leading to postischemic vasculogenesis. Methods and Results— MPs from mice ischemic hind-limb muscle were detected by electron microscopy 48 hours after unilateral femoral artery ligation as vesicles of 0.1- to 1-μm diameter. After isolation by sequential centrifugation, flow cytometry analyses showed that the annexin V + MP concentration was 3.5-fold higher in ischemic calves than control muscles (1392±406 versus 394±180 annexin V + MPs per 1 mg; P 144+ ). MPs isolated from ischemic muscles induced more potent in vitro bone marrow–mononuclear cell (BM-MNC) differentiation into cells with endothelial phenotype than those isolated from control muscles. MPs isolated from atherosclerotic plaques were ineffective, whereas those isolated from apoptotic or interleukin-1β–activated endothelial cells also promoted BM-MNC differentiation. Interestingly, MPs from ischemic muscles produced more reactive oxygen species and expressed significantly higher levels of NADPH oxidase p47 (6-fold; P P P Conclusion— MPs produced during tissue ischemia stimulate progenitor cell differentiation and subsequently promote postnatal neovascularization.