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Procoagulant Platelet Characterization by Measuring Phosphatidylserine Exposure and Microvesicle Release from Human Purified Platelets
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Factor Va, bound to microparticles released during platelet storage, is resistant to inactivation by activated

Elke J P Magdeleyns1, Jeffrey F W Keuren, Joyce Curvers

  • 1Sanquin Blood Bank Southeast Region, Maastricht, The Netherlands.

Transfusion
|September 21, 2007
PubMed
Abstract

Insights

Microparticles (MPs) shed from stored platelets resist anticoagulant effects, unlike those on synthetic vesicles. This resistance of factor Va on MPs enhances their procoagulant activity, impacting hemostasis in patients.

Area of Science:

  • Hematology
  • Biochemistry
  • Thrombosis Research

Background:

  • Microparticles (MPs) are known to support blood coagulation.
  • The role of MPs in restoring hemostasis in thrombocytopenic patients is recognized.
  • Anticoagulant properties of MPs from stored platelets remain uninvestigated.

Purpose of the Study:

  • To investigate the anticoagulant properties of microparticles (MPs) shed during platelet (PLT) storage.
  • To determine if factor Va (FVa) is present on storage-induced MPs and its susceptibility to activated protein C (APC).

Main Methods:

  • Harvesting storage-induced MPs from outdated platelet concentrates.
  • Assessing FVa presence on MP surfaces.
  • Determining APC-catalyzed inactivation of MP-bound FVa.
  • Comparing FVa inactivation on MPs, thrombin-activated PLTs, and synthetic vesicles.

Main Results:

  • Storage-induced MPs carry FVa on their surface.
  • MP-bound FVa exhibits significant resistance to APC-catalyzed inactivation (42% residual activity) compared to FVa on synthetic vesicles (5% residual activity).
  • Thrombin generation assays confirmed an APC-resistant phenotype for MPs, showing higher residual FVa activity (87%) in their presence.

Conclusions:

  • The surface environment of storage-induced MPs confers resistance to APC-mediated inactivation of FVa.
  • This APC resistance enhances the procoagulant potential of MPs derived from stored platelets.

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