[Show abstract][Hide abstract] ABSTRACT: Osteoprotegerin (OPG), a soluble tumour necrosis factor receptor superfamily member, inhibits RANKL-mediated osteoclastogenesis. We have previously reported that OPG enhances the proangiogenic properties of endothelial colony-forming cells (ECFCs) in vitro, and promotes vasculogenesis in vivo. Here we investigated how OPG promotes neovascularisation. Proteomic experiments showed that OPG pretreatment affected ECFCs protein expression in two ways, 23 spots being down-regulated and 6 upregulated. These spots corresponded to proteins involved in cell motility, adhesion, signal transduction and apoptosis. In keeping with these proteomic results, we found that OPG induced ECFCs adhesion to activated endothelium in shear stress conditions, promoting intermediate but not focal adhesion to fibronectin and collagen. Treatment with OPG induced a reorganization of the ECFCs cytoskeleton, with the emergence of cell protrusions characteristic of a migratory phenotype. These effects correlated with decreased FAK phosphorylation and enhanced integrin α(V)β(3) expression. OPG drastically reduced caspase-3/7 activities and maintained ECFCs viability after 48 h of treatment. All these effects were significantly attenuated by ECFCs incubation with the CXCR4 antagonist AMD-3100, and by prior heparan sulphate proteoglycan disruption. The proangiogenic properties of OPG appeared to be mediated by the proteoglycan syndecan-1, although OPG 1-194 lacking its heparin-binding domain still had pro-vasculogenic effects in vitro and in vivo. These results suggest that OPG may interact with ECFCs by binding to HSPGs/syndecan-1, thereby induce an anti-adhesive effect and promoting ECFCs migration through a SDF-1/CXCR4 dependent pathway.
[Show abstract][Hide abstract] ABSTRACT: Thrombospondin-1 (TSP-1) gives rise to fragments that have both pro- and anti-angiogenic effects in vitro and in vivo. The TSP-HepI peptide (2.3kDa), located in the N-terminal domain of TSP-1, has proangiogenic effects on endothelial cells. We have previously shown that TSP-1 itself exhibits a dual effect on endothelial colony-forming cells (ECFC) by enhancing their adhesion through its TSP-HepI fragment while reducing their proliferation and differentiation into vascular tubes (tubulogenesis) in vitro. This effect is likely mediated through CD47 binding to the TSP-1 C-terminal domain. Here we investigated the effect of TSP-HepI peptide on the angiogenic properties of ECFC in vitro and in vivo. TSP-HepI peptide potentiated FGF-2-induced neovascularisation by enhancing ECFC chemotaxis and tubulogenesis in a Matrigel plug assay. ECFC exposure to 20μg/mL of TSP-HepI peptide for 18h enhanced cell migration (p<0.001 versus VEGF exposure), upregulated alpha 6-integrin expression, and enhanced their cell adhesion to activated endothelium under physiological shear stress conditions at levels comparable to those of SDF-1α. The adhesion enhancement appeared to be mediated by the heparan sulfate proteoglycan (HSPG) syndecan-4, as ECFC adhesion was significantly reduced by a syndecan-4-neutralising antibody. ECFC migration and tubulogenesis were stimulated neither by a TSP-HepI peptide with a modified heparin-binding site (S/TSP-HepI) nor when the glycosaminoglycans (GAGs) moieties were removed from the ECFC surface by enzymatic treatment. Ex vivo TSP-HepI priming could potentially serve to enhance the effectiveness of therapeutic neovascularisation with ECFC.
[Show abstract][Hide abstract] ABSTRACT: Fucoidan, an antithrombotic polysaccharide, can induce endothelial colony-forming cells (ECFC) to adopt an angiogenic phenotype in vitro.
We evaluated the effect of fucoidan on vasculogenesis induced by ECFC in vivo.
We used a murine hindlimb ischemia model to probe the synergic role of fucoidan-treatment and ECFC infusion during tissue repair.
We found that exposure of ECFC to fucoidan prior to their intravenous injection improved residual muscle blood flow and increased collateral vessel formation. Necrosis of ischemic tissue was significantly reduced on day 14, to 12.1% of the gastronecmius cross-sectional surface area compared with 40.1% in animals injected with untreated-ECFC. ECFC stimulation with fucoidan caused a rapid increase in cell adhesion to activated endothelium in flow conditions, and enhanced transendothelial extravasation. Fucoidan-stimulated ECFC were resistant to shear stresses of up to 21 dyn cm(-2). Direct binding assays showed strong interaction of fucoidan with displaceable binding sites on the ECFC membrane. Bolus intramuscular administration of fucoidan 1 day after surgery reduces rhabdomyolysis. Mice injected with fucoidan (15 mg kg(-1)) had significantly lower mean serum creatine phosphokinase (CPK) activity than control animals. This CPK reduction was correlated with muscle preservation against necrosis (P < 0.001).
Fucoidan greatly increases ECFC-mediated angiogenesis in vivo. Its angiogenic effect would be due in part to its transportation to the ischemic site and its release after displacement by proteoglycans present in the extracellular matrix. The use of ECFC and fucoidan together, will be an efficient angiogenesis strategy to provide therapeutic neovascularization.
Journal of Thrombosis and Haemostasis 11/2011; 10(1):38-48. DOI:10.1111/j.1538-7836.2011.04554.x · 5.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: New antithrombotic agents with the potential to prevent atherothrombotic complications are being developed to target receptors on platelets and other cells involved in plaque growth. The aim of this study was to investigate the antiplatelet effects of F 16618, a new non-peptidic PAR1 (thrombin receptor) antagonist.
We investigated the inhibitory effect of F 16618 on human platelet aggregation ex vivo, in whole blood and washed platelets, by using a multiple-electrode platelet aggregometer based on impedance and an optical aggregometer, respectively. Its effects on whole-blood haemostasis (clot parameters) were analysed with the ROTEM thromboelastometry device and the platelet function analyser PFA-100. A guinea-pig model of arterial thrombosis was used to investigate its effects on thrombus formation in vivo.
F 16618 inhibited PAR1 agonist peptide (SFLLR-peptide)-induced washed platelet aggregation ex vivo. This effect was concentration-dependent and exhibited a competitive inhibition profile. Washed platelet aggregation, as well as P-selectin expression induced by thrombin, were significantly inhibited by 10 µM F 16618. In whole-blood experiments, 20 µM F 16618 inhibited SFLLR-induced platelet aggregation by 49%. In contrast, it had no effect on whole-blood haemostasis. In the guinea-pig model of carotid thrombosis, 0.32 mg·kg(-1) F 16618 doubled the occlusion time.
F 16618 was shown to have strong antithrombotic activity in vivo and moderate antiplatelet effects ex vivo. As these effects were not associated with major effects on physiological haemostasis, this molecule is a good antiplatelet drug candidate for use either alone or in combination with current treatments.
British Journal of Pharmacology 09/2011; 165(6):1827-35. DOI:10.1111/j.1476-5381.2011.01668.x · 4.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To determine the role of Wnt antagonist Dickkopf (DKK) 1 in human endothelial colony-forming cells (ECFCs) in view of the emerging importance of Wnt pathways in vascular biology.
Endothelial progenitor cells have been proposed to be crucial in tumor neovascularization. Recombinant DKK1 has been tested in ECFC angiogenic properties in vitro. DKK1 enhanced ECFC proliferation and the capacity of ECFCs to form pseudotubes in Matrigel. These effects have been attributed to enhancement of vascular endothelial growth factor receptor 2, SDF-1, and CXCR4. DKK1 gene silencing has been realized on ECFCs and mesenchymal stem cells, and we found that DKK1 silencing in the 2 cell types decreased their angiogenic potential. We then examined the possible role of DKK1 in tumor neovasculogenesis and found that blood vessels of breast cancer tissues expressed DKK1 far more strongly in human breast tumors than in normal breast tissues. By studying 62 human breast tumors, we found a significant positive correlation between DKK1 expression and von Willebrand factor. In vivo, DKK1 strongly enhanced the vascularization of Matrigel plugs and increased tumor size in a xenograft model of human breast carcinoma in nude mice.
DKK1 enhances angiogenic properties of ECFCs in vitro and is required for ECFC and mesenchymal stem cell angiogenic phenotypes in vivo. DKK1 also increases tumoral angiogenesis. Thus, we demonstrated a major role of DKK1 in angiogenic processes.
[Show abstract][Hide abstract] ABSTRACT: Combined antiplatelet agents (cAPA), aspirin plus clopidogrel, increase the risk of bleeding. We hypothesised that recombinant activated FVIIa (rFVIIa), which normalises thrombin generation in platelet-rich plasma from patients treated with cAPA, could limit this bleeding risk. It was the objective of this study to investigate the efficacy and safety of rFVIIa compared to placebo, in a bleeding and thrombosis model in rabbits treated with aspirin and clopidogrel. New-Zealand rabbits, randomised into two groups (Placebo1, n=36 ; cAPA, n=34), were anaesthetised, ventilated and monitored for blood pressure, temperature and carotid blood flow. The Folts model was applied to a carotid artery. Cyclic flow reductions (CFR) were recorded over a first 20-min period (Obs1). Each rabbit was then randomly assigned into one of three subgroups (Placebo2, 40μg/kg rFVIIa, 160 μg/kg rFVIIa) and CFR were monitored for a second 20-min period (Obs2). Ear bleeding time (BT) was measured at the end of each period. Hepatosplenic (HS) section was performed at the end of the experiment and HS blood loss defines the primary endpoint. Secondary endpoints were thrombosis (CFR), prothrombin time, platelet aggregation, and thrombin generation. Non- parametric statistical tests were used (p<0.05). cAPA significantly increased HS blood loss, BT and suppressed CFR compared to Placebo1 (p<0.05). rFVIIa injection did not modify HS blood loss, BT or CFR rate in Placebo1 rabbits nor in cAPA animals. These effects were unaffected by either rFVIIa dose. rFVIIa accelerated thrombin generation but had no effect on platelet aggregation in citrated platelet-rich plasma. rFVIIa did not modify HS blood loss associated with cAPA in rabbits.
Thrombosis and Haemostasis 10/2010; 104(4):823-30. DOI:10.1160/TH10-01-0039 · 4.98 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Lowe syndrome (LS) is a rare X-linked disorder caused by mutations in the oculocerebrorenal gene (OCRL), encoding OCRL, a phosphatidylinositol 5-phosphatase with a RhoGAP domain. An abnormal rate of haemorrhagic events was found in a retrospective clinical survey. Herein, we report the results of exploration of haemostasis in six LS patients. All patients had normal coagulation tests but prolonged closure times (CTs) in the PFA-100 system. Healthy donors' blood samples incubated with a RhoA kinase inhibitor had prolonged CTs. This suggests that an aberrant RhoA pathway in platelets contributes to CT prolongation and primary haemostasis disorders in LS.
British Journal of Haematology 09/2010; 150(6):685-8. DOI:10.1111/j.1365-2141.2010.08304.x · 4.71 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The proinflammatory chemokine interleukin 8 exerts potent angiogenic effects on endothelial cells by interacting with its receptors CXCR1 and CXCR2. As thrombin is also a potent inflammatory factor, and as endothelial progenitor cells (EPC) express functional PAR-1 thrombin receptor, we examined whether PAR-1 stimulation interferes with the IL-8 pathway in EPC. EPC were obtained from adult blood (AB) and cord blood (CB). The effect of PAR-1 stimulation by the peptide SFLLRN on IL-8, CXCR1 and CXCR2 expression was examined by RTQ-PCR and at the protein level in AB and CB late EPC and in AB early EPC. Specific siRNA was used to knock down PAR-1 expression. The IL-8 gene was expressed strongly in AB early EPC and moderately in late EPC. In contrast, CXCR1 and CXCR2 gene expression was restricted to AB early EPC. The IL-8 level in AB early EPC conditioned medium was high in basal conditions and did not change after PAR-1 activation. By contrast, IL-8 secretion by late EPC was low in basal conditions and strongly up-regulated upon PAR-1 activation. PAR-1 activation induced a number of genes involved in activating protein-1 (AP-1) and nuclear factor (NF)-kappaB pathways. Conditioned medium of PAR-1-activated late EPC enhanced the migratory potential of early EPC, and this effect was abrogated by blocking IL-8. Target-specific siRNA-induced PAR-1 knockdown, and fully inhibited PAR-1-induced IL-8 synthesis. In conclusion, PAR-1 activation induces IL-8 synthesis by late EPC. This could potentially enhance cooperation between late and early EPC during neovascularization, through a paracrine effect.
Journal of Cellular and Molecular Medicine 08/2009; 13(8B):2534-46. DOI:10.1111/j.1582-4934.2008.00429.x · 4.01 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Les progéniteurs endothéliaux circulants (PEC) possèdent des propriétés angiogéniques et la modulation de leur nombre et de leurs fonctions représente un axe de recherche en thérapie cellulaire des pathologies ischémiques.
La VE-statine (Egfl7) est une protéine de découverte récente d’expression principalement endothéliale, et régulant la tubulogenèse, l’élastogenèse, l’intégrité vasculaire et la migration des cellules musculaires lisses. Toutefois, son rôle dans la vasculogenèse post-natale n’est pas parfaitement élucidé.
Nous avons étudié le rôle de la VE-statine dans la biologie des PEC tardifs isolés à partir de sang adulte et de sang de cordon. Les modèles classiques d’angiogenèse in vitro (formation de pseudo-tubes en matrigel, test de prolifération au pNPP et test de migration par scratch test) et in vivo (modèle d’implant de matrigel sous cutané chez la souris C57/Bl6) ont été utilisés. La VE-statine a été produite en milieu conditionné (fibroblastes 3T3 transfectés avec la construction plasmidique pVE-statine- HA). L’inhibition de l’expression de la VE-statine dans les PEC a été réalisée par l’utilisation de siRNA par lipofection avec le kit Primefect (LONZA®).
Nos résultats montrent que le milieu conditionné contenant la VE-statine inhibe la différenciation des PEC tardifs de 95 %, leur prolifération de 96 % et leur migration après blessure de 34 %. Inversement, l’inhibition de 90 % de l’expression du gène de la VE-statine avec un siRNA entraîne une augmentation de leur différenciation, prolifération et migration. L’ajout de VE-statine au basic Fibrobast Growth Factor dans un modèle pré-clinique d’implant de matrigel sous cutané chez la souris, induit une inhibition importante de la vascularisation des implants.
Ces résultats suggèrent que la VE-statine est un régulateur négatif des propriétés des PEC et son inhibition pourrait être une cible pour augmenter l’expansion et le potentiel angiogénique des PEC.