title: Direct observation of von Willebrand factor elongation and fiber formation on collagen during acute whole blood exposure to pathological flow.
abstract: OBJECTIVE
  In severe stenosis, von Willebrand factor (vWF) experiences millisecond exposures to pathological wall shear rates (γ(w)). We sought to evaluate the deposition of vWF onto collagen surfaces under flow in these environments.
  
  
  RESULTS
  Distinct from viscometry experiments that last many seconds, we deployed microfluidic devices for single-pass perfusion of whole blood or platelet-free plasma over fibrillar type 1 collagen (<50 ms transit time) at pathological γ(w) or spatial wall shear rate gradients (grad γ(w)). Using fluorescent anti-vWF, long thick vWF fibers (>20 μm) bound to collagen were visualized at constant γ(w)>30000 s(-1) during perfusion of platelet-free plasma, a process enhanced by EDTA. Rapid acceleration or deceleration of EDTA platelet-free plasma at grad γ(w)=±1.1×10(5) to ±4.3×10(7) s(-1)/cm did not promote vWF deposition. At 19400 s(-1), EDTA blood perfusion resulted in rolling vWF-platelet nets, although blood perfusion (normal Ca(2+)) generated large vWF/platelet deposits that repeatedly embolized and were blocked by anti-glycoprotein Ib or the α(IIb)β(3) inhibitor GR144053 and did not require grad γ(w). Blood perfusion at venous shear rate (200 s(-1)) produced a stable platelet deposit that was a substrate for massive but unstable vWF-platelet aggregates when flow was increased to 7800 s(-1).
  
  
  CONCLUSIONS
  Triggered by collagen and enhanced by platelet glycoprotein Ib and α(IIb)β(3), vWF fiber formation occurred during acute exposures to pathological γ(w) and did not require gradients in wall shear rate.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Institute for Medicine and Engineering, 1024 Vagelos Research Laboratory, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Thomas V
authors.initials: TV
authors.lastname: Colace
authors.forename: Scott L
authors.initials: SL
authors.lastname: Diamond
mesh_terms: D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D024042:Collagen Type I / Q000378:metabolism*; D006801:Humans; D008297:Male; D046210:Microfluidic Analytical Techniques; D008856:Microscopy, Fluorescence; D010973:Platelet Adhesiveness; D010974:Platelet Aggregation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000378:metabolism; D012039:Regional Blood Flow; D013314:Stress, Mechanical; D013927:Thrombosis / Q000097:blood* / Q000503:physiopathology; D013997:Time Factors; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D024042:Collagen Type I; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D019038:Platelet Glycoprotein GPIb-IX Complex; D014841:von Willebrand Factor; D002118:Calcium