title: Murine hematopoietic cell tissue factor pathway inhibitor limits thrombus growth.
abstract: OBJECTIVE
  Tissue factor (TF)-factor VIIa initiates blood coagulation and is found on microparticles that accumulate within intravascular thrombi. Tissue factor pathway inhibitor (TFPI), a factor Xa (fXa)-dependent inhibitor of TF-factor VIIa, is produced by megakaryocytes and is present in platelets. We sought to determine the role of platelet TFPI in regulation of thrombus growth.
  
  
  RESULTS
  Western blot analyses demonstrated that murine platelets produce TFPIα, the most evolutionarily conserved alternatively spliced isoform of TFPI. A mouse model of hematopoietic cell TFPI deficiency was developed by transplanting irradiated TFPI(+/-) mice with TFPI(-/-) fetal liver cells. Platelets from transplanted mice totally lack TFPI inhibitory activity. An electrolytic vascular injury model was used to assess thrombus growth in the femoral vein and carotid artery. Mice lacking hematopoietic TFPI developed larger femoral vein and carotid artery thrombi than TFPI(+/-) mice transplanted with TFPI(+/+) hematopoietic cells, as evidenced by increased platelet accumulation.
  
  
  CONCLUSIONS
  Hematopoietic TFPI limits thrombus growth following vascular injury. Because platelets are the primary hematopoietic cell accumulating within a growing thrombus, these findings suggest that TFPI present within platelets functions to limit intravascular thrombus growth, likely through inhibition of the procoagulant activity of blood borne TF.
authors.affiliation: Blood Research Institute, Blood Center of Wisconsin, Milwaukee, WI 53201-2178, USA.
authors.forename: Susan A
authors.initials: SA
authors.lastname: Maroney
authors.forename: Brian C
authors.initials: BC
authors.lastname: Cooley
authors.forename: Josephine P
authors.initials: JP
authors.lastname: Ferrel
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Bonesho
authors.forename: Alan E
authors.initials: AE
authors.lastname: Mast
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D001777:Blood Coagulation / Q000235:genetics; D001792:Blood Platelets / Q000378:metabolism*; D015153:Blotting, Western; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D022781:Hepatocytes / Q000378:metabolism / Q000637:transplantation; D008074:Lipoproteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008099:Liver / Q000196:embryology / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D013927:Thrombosis / Q000097:blood / Q000235:genetics / Q000517:prevention & control*; D013997:Time Factors; D020246:Venous Thrombosis / Q000097:blood / Q000235:genetics / Q000517:prevention & control*; D014916:Whole-Body Irradiation
chemical_list: D008074:Lipoproteins; C051928:lipoprotein-associated coagulation inhibitor