PI3 kinase-dependent stimulation of platelet migration by stromal cell-derived factor 1 (SDF-1).

Platelets have been regarded as static cells that do not move once they adhere to a matrix. The present study explored, whether platelets are able to migrate. In contrast to the current opinion, we found that platelets were mobile, able to migrate over a surface, and transmigrate through a transwell membrane and endothelium toward a source of stromal cell-derived factor 1 (SDF-1). Platelet migration was stimulated by SDF-1, which led to the downstream activation and phosphorylation of Wiskott-Aldrich syndrome protein. SDF-1 signaling and subsequent platelet migration could be inhibited by CXCR4-receptor blocker AMD3100, pertussis toxin, inhibition of phosphoinositol 3-kinase (PI3 kinase) with LY294002 or wortmannin, and disruption of actin polymerization with cytochalasin B. The potential of platelets to migrate in an SDF-1-mediated fashion may redefine the role of platelets in the pathophysiology of vascular inflammation, subsequent atherosclerotic degeneration, and vascular regeneration.

Impact of inflammatory state and metabolic control on responsiveness to dual antiplatelet therapy in type 2 diabetics after PCI: prognostic relevance of residual platelet aggregability in diabetics undergoing coronary interventions.

BACKGROUND: Type-2 diabetes is accompanied by a prothrombotic state influenced by endothelial dysfunction, inflammatory condition and platelet hyperreagibility. We aimed to characterize the relationship of inflammation and residual platelet aggregability (RPA) under antiplatelet therapy with regard to prognosis in an unselected PCI-cohort of diabetics. METHODS: In a first step, a consecutive collective of 75 type 2 diabetics compared to 153 non-diabetic controls was evaluated at the time of PCI. Inflammatory markers, Interleukin 6 and C-reactive protein were measured by immunoassays. ADP and Aspirin assays were performed by multiple electrode aggregometry. Then, we consecutively evaluated ADP-induced RPA in 542 diabetics and 1,161 non-diabetics undergoing PCI and treated by standard antiplatelet therapy. Major CV-events were assessed at 30 days after PCI. RESULTS: Inflammatory markers were significantly increased in diabetics with peri-interventional hyperglycemic state and inversely correlated with responsiveness to clopidogrel and aspirin. In a large scale cohort, diabetics showed a higher RPA compared to non-diabetics (median 38.1 vs. 28.8%; p < 0.001). After adjustment for relevant co-factors, diabetes remained a strong predictor for increased RPA (OR 4.39; 95% CI 1.95-6.83; p < 0.001). Furthermore, diabetics with high RPA had an increased risk for 30-day MI and CV-death than diabetics with low RPA (adjusted HR 1.05; 95% CI 1.02-1.07; p < 0.001). CONCLUSIONS: We demonstrate that peri-interventional inflammatory degree and glycaemic control correlate with decreased antiplatelet drug responsiveness in diabetics. In addition, we identified high RPA as strong predictor for short-term CV-events in this group. Therefore, approaches to treat these entities are needed to improve outcome in diabetics undergoing PCI.

Junctional adhesion molecule A expressed on human CD34+ cells promotes adhesion on vascular wall and differentiation into endothelial progenitor cells.

OBJECTIVE: To investigate the role of junctional adhesion molecule A (JAM-A) on adhesion and differentiation of human CD34(+) cells into endothelial progenitor cells. METHODS AND RESULTS: Tissue healing and vascular regeneration is a multistep process requiring firm adhesion of circulating progenitor cells to the vascular wall and their further differentiation into endothelial cells. The role of JAM-A in platelet-mediated adhesion of progenitor cells was investigated by adhesion assays in vitro and with the help of intravital fluorescence microscopy in mice. Preincubation of human CD34(+) progenitor cells with soluble JAM-A-Fc (sJAM-A-Fc) resulted in significantly decreased adhesion over immobilized platelets or inflammatory endothelium under high shear stress in vitro and after carotid ligation in vivo or ischemia/reperfusion injury in the microcirculation of mice. Human CD34(+) cells express JAM-A, as defined by flow cytometry and Western blot analysis. JAM-A mediates differentiation of CD34(+) cells to endothelial progenitor cells and facilitates CD34(+) cell-induced reendothelialization in vitro. Pretreatment of human CD34(+) cells with sJAM-A-Fc resulted in increased neointima formation 3 weeks after endothelial denudation in the carotid arteries of nonobese diabetic/severe combined immunodeficient mice. CONCLUSIONS: These results indicate that the expression of JAM-A on CD34(+) cells mediates adhesion to the vascular wall after injury and differentiation into endothelial progenitor cells, a mechanism potentially involved in vascular regeneration. Human CD34(+) cells express JAM-A, mediating their interaction with platelets and endothelial cells. Specifically, JAM-A expressed on human CD34(+) progenitor cells regulates their adhesion over immobilized platelets or inflammatory endothelium under high shear stress in vitro and after carotid ligation in vivo or ischemia/reperfusion injury in the microcirculation of mice. Moreover, it mediates differentiation of CD34(+) cells to endothelial progenitor cells and facilitates reendothelialization.

Endothelial nitric oxide synthase activity is essential for vasodilation during blood flow recovery but not for arteriogenesis.

OBJECTIVE: Arteriogenesis is the major mechanism of vascular growth, which is able to compensate for blood flow deficiency after arterial occlusion. Endothelial nitric oxide synthase (eNOS) activity is essential for neovascularization, however its specific role in arteriogenesis remains unclear. We studied the role of eNOS in arteriogenesis using 3 mouse strains with different eNOS expression. METHODS AND RESULTS: Distal femoral artery ligation was performed in eNOS-overexpressing mice (eNOStg), eNOS-deficient (eNOS-/-) mice, and wild type (WT) controls. Tissue perfusion and collateral-dependent blood flow were significantly increased in eNOStg mice compared with WT only immediately after ligation. In eNOS-/- mice, although tissue perfusion remained significantly decreased, collateral-dependent blood flow was only decreased until day 7, suggesting normal, perhaps delayed collateral growth. Histology confirmed no differences in collateral arteries of eNOStg, eNOS-/-, and WT mice at 1 and 3 weeks. Administration of an NO donor induced vasodilation in collateral arteries of eNOS-/- mice, but not in WT, identifying the inability to vasodilate collateral arteries as main cause of impaired blood flow recovery in eNOS-/- mice. CONCLUSIONS: This study demonstrates that eNOS activity is crucial for NO-mediated vasodilation of peripheral collateral vessels after arterial occlusion but not for collateral artery growth.

Divergent effects of GM-CSF and TGFbeta1 on bone marrow-derived macrophage arginase-1 activity, MCP-1 expression, and matrix metalloproteinase-12: a potential role during arteriogenesis.

Granulocyte/macrophage-colony stimulating factor (GM-CSF) and transforming growth factor (TGF)beta1 induce arteriogenesis in a nonischemic model of femoral artery ligation. Moreover, clinical trials demonstrated an improved collateralization after injection of bone marrow cells. In the present study, the expression of arteriogenic factors in bone marrow-derived macrophages (BMDM) was measured to verify the potential of these cells to influence collateral artery growth. GM-CSF induced in BMDM the expression of monocyte chemoattractive protein (MCP)-1, matrix-metalloproteinase (MMP)-12, and arginase-1-the latter also showing a remarkable increase in activity. During in vivo induced arteriogenesis, the accumulation rate of macrophages around proliferating collaterals was significantly increased. We also show that MCP-1 is found to be mainly expressed in the media of the vessel wall, MMP-12 in macrophages of the adventitia, and arginase at both locations. This study provides for the first time a comprehensive analysis of GM-CSF/TGFbeta1-regulated arteriogenic factors in BMDM and supports the hypothesis that arteriogenesis is a multistage mechanism, including monocyte/macrophage adhesion and transmigration, pro-arteriogenic cytokine expression, degradation of connective tissue, and collagen synthesis regulation. Selective modulation of these mechanisms as well as cell-based therapies supplying arteriogenic factors in vivo point toward new strategies to influence collateral artery growth.