title: Fibrin, γ'-fibrinogen, and transclot pressure gradient control hemostatic clot growth during human blood flow over a collagen/tissue factor wound.
abstract: OBJECTIVE
  Biological and physical factors interact to modulate blood response in a wounded vessel, resulting in a hemostatic clot or an occlusive thrombus. Flow and pressure differential (ΔP) across the wound from the lumen to the extravascular compartment may impact hemostasis and the observed core/shell architecture. We examined physical and biological factors responsible for regulating thrombin-mediated clot growth.
  
  
  RESULTS
  Using factor XIIa-inhibited human whole blood perfused in a microfluidic device over collagen/tissue factor at controlled wall shear rate and ΔP, we found thrombin to be highly localized in the P-selectin(+) core of hemostatic clots. Increasing ΔP from 9 to 29 mm Hg (wall shear rate=400 s(-1)) reduced P-selectin(+) core size and total clot size because of enhanced extravasation of thrombin. Blockade of fibrin polymerization with 5 mmol/L Gly-Pro-Arg-Pro dysregulated hemostasis by enhancing both P-selectin(+) core size and clot size at 400 s(-1) (20 mm Hg). For whole-blood flow (no Gly-Pro-Arg-Pro), the thickness of the P-selectin-negative shell was reduced under arterial conditions (2000 s(-1), 20 mm Hg). Consistent with the antithrombin-1 activity of fibrin implicated with Gly-Pro-Arg-Pro, anti-γ'-fibrinogen antibody enhanced core-localized thrombin, core size, and overall clot size, especially at venous (100 s(-1)) but not arterial wall shear rates (2000 s(-1)). Pathological shear (15 000 s(-1)) and Gly-Pro-Arg-Pro synergized to exacerbate clot growth.
  
  
  CONCLUSIONS
  Hemostatic clotting was dependent on core-localized thrombin that (1) triggered platelet P-selectin display and (2) was highly regulated by fibrin and the transclot ΔP. Also, γ'-fibrinogen had a role in venous but not arterial conditions.
authors.affiliation: From the Department of Chemical and Biomolecular Engineering (R.W.M., J.D.W., S.L.D.) and Department of Medicine (J.D.W., L.F.B.), University of Pennsylvania, Philadelphia.
authors.forename: Ryan W
authors.initials: RW
authors.lastname: Muthard
authors.affiliation: From the Department of Chemical and Biomolecular Engineering (R.W.M., J.D.W., S.L.D.) and Department of Medicine (J.D.W., L.F.B.), University of Pennsylvania, Philadelphia.
authors.forename: John D
authors.initials: JD
authors.lastname: Welsh
authors.affiliation: From the Department of Chemical and Biomolecular Engineering (R.W.M., J.D.W., S.L.D.) and Department of Medicine (J.D.W., L.F.B.), University of Pennsylvania, Philadelphia.
authors.forename: Lawrence F
authors.initials: LF
authors.lastname: Brass
authors.affiliation: From the Department of Chemical and Biomolecular Engineering (R.W.M., J.D.W., S.L.D.) and Department of Medicine (J.D.W., L.F.B.), University of Pennsylvania, Philadelphia. sld@seas.upenn.edu.
authors.forename: Scott L
authors.initials: SL
authors.lastname: Diamond
mesh_terms: D000818:Animals; D001158:Arteries / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D001783:Blood Flow Velocity; D024042:Collagen Type I / Q000097:blood*; D004195:Disease Models, Animal; D005337:Fibrin / Q000378:metabolism*; D015241:Fibrinogens, Abnormal / Q000378:metabolism*; D006487:Hemostasis; D006801:Humans; D056656:Lab-On-A-Chip Devices; D008297:Male; D040542:Mechanotransduction, Cellular; D051379:Mice; D019007:P-Selectin / Q000097:blood; D058105:Polymerization; D011312:Pressure; D012039:Regional Blood Flow; D013314:Stress, Mechanical; D013917:Thrombin / Q000378:metabolism*; D013925:Thromboplastin / Q000378:metabolism*; D013927:Thrombosis / Q000097:blood* / Q000473:pathology / Q000503:physiopathology; D013997:Time Factors; D057772:Vascular System Injuries / Q000097:blood* / Q000473:pathology / Q000503:physiopathology; D014680:Veins / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology
chemical_list: D024042:Collagen Type I; D015241:Fibrinogens, Abnormal; D019007:P-Selectin; C546937:SELP protein, human; C527521:fibrinogen gamma'; D005337:Fibrin; D013925:Thromboplastin; D013917:Thrombin
keywords: fibrin; hemodynamics; hemostasis; thrombin