Ultrastructural analysis of thrombin-induced interaction between human platelets and liposomes carrying fibrinogen γ-chain dodecapeptide as a synthetic platelet substitute

Hidenori Suzuki, Yosuke Okamura, Yasuo Ikeda, Shinji Takeoka, Makoto Handa

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7 Citations (Scopus)

Abstract

Background: The dodecapeptide HHLGGAKQAGDV (H12) in the carboxy-terminus of the fibrinogen γ-chain is a specific binding site of the ligand for platelet GPIIb/IIIa complex. We have evaluated liposomes carrying fibrinogen γ-chain dodecapeptide as a synthetic platelet substitute. Objectives: We examined the interaction between human platelets and H12-liposomes during thrombin-induced activation using flow cytometry and electron microscopy (EM). Methods and results: After thrombin-activation, a remarkable time-dependent increase in binding of the H12-liposomes to platelets was found by flow cytometry. A large-sized swollen open canalicular system (OCS) was observed in the spheroidal platelets from 60 sec to 5 min after thrombin-activation, but intact H12-liposomes were not evident by conventional EM. Cryoultramicrotomy and immunogold staining with anti-H12 antibody were successful in identifying the liposomes; they appeared as small particles with a unit membrane around 0.2 to 0.4 μm in diameter, and gold labels representing H12 were distributed homogeneously on the surface. Abundant H12-liposomes were localized not only on the surface membrane but also in the lumen of the large-sized swollen OCS in the platelets at 60 sec after thrombin-activation. The formation of the large-sized swollen OCS was inhibited by pre-incubation with unbound H12, EDTA or anti-GPIIb/IIIa antibody. In thrombin-induced platelet aggregates we observed electron-transparent areas between adherent platelets, in which abundant H12-liposomes were distributed. Conclusions: We demonstrate morphologically that H12-liposomes bind to thrombin-activated platelets and accumulate between adherent platelets like fibrinogen, leading to large-scale aggregation.

Original languageEnglish
Pages (from-to)552-559
Number of pages8
JournalThrombosis Research
Volume128
Issue number6
DOIs
Publication statusPublished - 2011 Dec 1

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Keywords

  • Aggregation
  • Dodecapeptide (H12)
  • Electron microscopy
  • Liposomes
  • Platelet substitute
  • Platelets

ASJC Scopus subject areas

  • Hematology

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