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

作者：Suzuki Hidenori^*; Okamura Yosuke; Ikeda Yasuo; Takeoka Shinji; Handa Makoto

来源：Thrombosis Research, 2011, 128(6): 552-559.

DOI：10.1016/j.thromres.2011.07.031

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

Background: The dodecapeptide HHLGGAKQAGDV (H12) in the carboxy-terminus of the fibrinogen.-chain is a specific binding site of the ligand for platelet GPIIb/IIIa complex. We have evaluated liposomes carrying fibrinogen.-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 mu m 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.

• 出版日期2011-12
• 单位河北医科大学