title: Hierarchical organization in the hemostatic response and its relationship to 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.
authors.affiliation: Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA. tstalker@mail.med.upenn.edu
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Stalker
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Traxler
authors.forename: Jie
authors.initials: J
authors.lastname: Wu
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Wannemacher
authors.forename: Samantha L
authors.initials: SL
authors.lastname: Cermignano
authors.forename: Roman
authors.initials: R
authors.lastname: Voronov
authors.forename: Scott L
authors.initials: SL
authors.lastname: Diamond
authors.forename: Lawrence F
authors.initials: LF
authors.lastname: Brass
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D015703:Antigens, CD / Q000502:physiology; D001792:Blood Platelets / Q000502:physiology* / Q000648:ultrastructure; D005337:Fibrin / Q000378:metabolism; D051960:GTP-Binding Protein alpha Subunit, Gi2 / Q000378:metabolism; D006487:Hemostasis / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018482:Muscle, Skeletal / Q000187:drug effects / Q000293:injuries / Q000378:metabolism*; D015539:Platelet Activation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D058921:Purinergic P2Y Receptor Antagonists / Q000494:pharmacology; D058925:Receptors, Purinergic P2Y12 / Q000737:chemistry / Q000378:metabolism; D039961:Semaphorins / Q000502:physiology; D015398:Signal Transduction; D013917:Thrombin / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D015703:Antigens, CD; C093224:CD100 antigen; C548577:P2ry12 protein, mouse; D010975:Platelet Aggregation Inhibitors; D058921:Purinergic P2Y Receptor Antagonists; D058925:Receptors, Purinergic P2Y12; D039961:Semaphorins; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; C117446:cangrelor; D005337:Fibrin; D013917:Thrombin; D051960:GTP-Binding Protein alpha Subunit, Gi2