title: Enhanced binding of tissue factor-microparticles to collagen-IV and fibronectin leads to increased tissue factor activity  in vitro.
abstract: The role of tissue factor (TF)-containing microparticles in clot propagation has been established, but the ability of circulating microparticles to initiate coagulation has been disputed. However, TF-bearing microparticles, particularly endothelial-microparticles generated during disease, may interact with extracellular matrices which in turn can localise circulating TF to sites of injury. In order to examine this hypothesis  in vitro , microparticles were isolated from human coronary artery endothelial cells transfected to overexpress TF, tumour-necrosis factor  (TNF) α-treated cells or non-transfected cells lacking TF. The ability of microparticles to bind collagen-IV, fibronectin and fibrin was examined under static conditions and arterial shear rates (650 s⁻¹), and also in the presence of inhibitory antibodies against β1-, β3-, α3- and αv-integrins or an anti-TF antibody. TF-microparticles showed increases of up to 43% and 24% in adherence to collagen-IV and fibronectin, respectively, compared to control microparticles under shear flow. Furthermore, TF-containing microparticles, but not the transfected parent cells had increased levels of β1-integrin compared to TF-deficient microparticles. Pre-incubation of microparticles with a β1-integrin-blocking antibody counteracted the additional adhesion of TF-microparticles compared to control microparticles. Finally, adherence of TF microparticles to collagen-IV or fibronectin resulted in increased TF activity by concentrating TF onto the surface. In conclusion, the presence of TF within microparticles enhances the interactions of endothelial cell-derived microparticles with extracellular matrices in an integrin-dependent manner. Accumulation and localisation of these microparticles in turn results in the enhancement of TF activity. This may be an innate mechanism by which TF-bearing microparticles induce coagulation upon vascular injury.
authors.affiliation: Biomedical Section, Department of Biological Sciences, University of Hull, Cottingham Road, Hull, HU6 7RX, UK. C.Ettelaie@hull.ac.uk
authors.forename: Camille
authors.initials: C
authors.lastname: Ettelaie
authors.forename: Mary E W
authors.initials: ME
authors.lastname: Collier
authors.forename: Mah Pui
authors.initials: MP
authors.lastname: Mei
authors.forename: Yu Pei
authors.initials: YP
authors.lastname: Xiao
authors.forename: Anthony
authors.initials: A
authors.lastname: Maraveyas
mesh_terms: D019138:Antibodies, Blocking / Q000378:metabolism; D001777:Blood Coagulation; D055252:Cell-Derived Microparticles / Q000378:metabolism*; D002478:Cells, Cultured; D024141:Collagen Type IV / Q000378:metabolism*; D042783:Endothelial Cells / Q000378:metabolism*; D005337:Fibrin / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism*; D006801:Humans; D039422:Integrin alpha3 / Q000276:immunology / Q000378:metabolism; D039564:Integrin alphaV / Q000276:immunology / Q000378:metabolism; D019012:Integrin beta1 / Q000276:immunology / Q000378:metabolism; D039661:Integrin beta3 / Q000276:immunology / Q000378:metabolism; D011485:Protein Binding; D013925:Thromboplastin / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D019138:Antibodies, Blocking; D024141:Collagen Type IV; D005353:Fibronectins; C061248:ITGB3 protein, human; D039422:Integrin alpha3; D039564:Integrin alphaV; D019012:Integrin beta1; D039661:Integrin beta3; D014409:Tumor Necrosis Factor-alpha; D005337:Fibrin; D013925:Thromboplastin