title: Cellular procoagulant activity dictates clot structure and stability as a function of distance from the cell surface.
abstract: BACKGROUND
  Thrombin concentration modulates fibrin structure and fibrin structure modulates clot stability; however, the impact of localized, cell surface-driven in situ thrombin generation on fibrin structure and stability has not previously been evaluated.
  
  
  RESULTS
  Human fibroblasts were incubated with factors Xa, Va, prothrombin and fibrinogen, or plasma. Fibrin formation, structure, and lysis were examined using laser scanning confocal microscopy and transmission electron microscopy. In situ thrombin generation on the cell surface produced clots with a significantly denser fiber network in a 10-microm region proximal versus distal to (40 to 50 microm) the cell surface. This morphology was not altered by addition of integrin-blocking RGDS peptide and was not apparent in clots made by exogenous thrombin addition, suggesting that spatial morphology was dictated predominantly by localized thrombin generation on the fibroblast surface. The fibrin network lysed more rapidly distal versus proximal to the cell surface, suggesting that the structural heterogeneity of the clot affected its fibrinolytic stability.
  
  
  CONCLUSIONS
  In situ thrombin generation on the cell surface modulates the three-dimensional structure and stability of the clot. Thrombus formation in vivo may reflect the ability of the local cell population to support thrombin generation and, therefore, the three-dimensional structure and stability of the fibrin network.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7525, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Campbell
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Overmyer
authors.forename: C Robert
authors.initials: CR
authors.lastname: Bagnell
authors.forename: Alisa S
authors.initials: AS
authors.lastname: Wolberg
mesh_terms: D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D015943:Factor Va / Q000378:metabolism / Q000494:pharmacology; D015951:Factor Xa / Q000378:metabolism / Q000494:pharmacology; D005337:Fibrin / Q000737:chemistry / Q000378:metabolism*; D005340:Fibrinogen / Q000378:metabolism / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D006801:Humans; D066298:In Vitro Techniques; D016023:Integrins / Q000378:metabolism; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D009842:Oligopeptides / Q000494:pharmacology; D011516:Prothrombin / Q000378:metabolism / Q000494:pharmacology; D013917:Thrombin / Q000096:biosynthesis*; D013927:Thrombosis / Q000209:etiology* / Q000378:metabolism / Q000473:pathology
chemical_list: D016023:Integrins; D009842:Oligopeptides; D015943:Factor Va; D011516:Prothrombin; D005337:Fibrin; D005340:Fibrinogen; C046617:arginyl-glycyl-aspartyl-serine; D013917:Thrombin; D015951:Factor Xa