Blood Journal
Leading the way in experimental and clinical research in hematology

Hierarchical organization in the hemostatic response and its relationship to the platelet-signaling network

  1. Timothy J. Stalker1,
  2. Elizabeth A. Traxler1,
  3. Jie Wu1,
  4. Kenneth M. Wannemacher1,
  5. Samantha L. Cermignano1,
  6. Roman Voronov2,
  7. Scott L. Diamond2, and
  8. Lawrence F. Brass1
  1. 1Departments of Medicine and Pharmacology and the
  2. 2Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA

Key Points

  • Hemostatic plugs develop a regional architecture defined by the extent of platelet activation and packing density.

  • The regional composition of a hemostatic plug is due to the interaction of local conditions with the platelet-signaling network.

Abstract

Achieving hemostasis following vascular injury requires the rapid accumulation of platelets and fibrin. Here we used a combination of confocal intravital imaging, genetically engineered mice, and antiplatelet agents to determine how variations in the extent of platelet activation following vascular injury arise from the integration of different elements of the platelet-signaling network. Two forms of penetrating injury were used to evoke the hemostatic response. Both produced a hierarchically organized structure in which a core of fully activated platelets was overlaid with an unstable shell of less-activated platelets. This structure emerged as hemostasis was achieved and persisted for at least 60 minutes following injury, its organization at least partly reflecting agonist concentration gradients. Thrombin activity and fibrin formation were found primarily in the innermost core. As proposed previously, greater packing density in the core facilitated contact-dependent signaling and limited entry of plasma-borne molecules visualized with fluorophores coupled to dextran and albumin. Blocking contact-dependent signaling or inhibiting thrombin reduced the size of the core, while the shell was heavily influenced by adenosine 5′-diphosphate and regulators of Gi2-mediated signaling. Thus, the hemostatic response is shown to produce a hierarchical structure arising, in part, from distinct elements of the platelet-signaling network.

  • Submitted September 19, 2012.
  • Accepted December 14, 2012.
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