title: Characterization of liposomes carrying von Willebrand factor-binding domain of platelet glycoprotein Ibalpha: a potential substitute for platelet transfusion.
abstract: Platelet glycoprotein (GP) Ib/IX/V complex is a receptor for von Willebrand factor (vWf), which plays a crucial role in primary hemostasis by mediating platelet adhesion to injured blood vessels. We have expressed in CHO cells a fragment of GPIba that retained a vWf-binding function. The recombinant fragment (rGPIba) was incorporated into liposomes and evaluated their functions in vitro. rGPIba on the liposome surface was detectable by flow cytometric analysis. Addition of vWf and ristocetin caused specific agglutination of rGPIbalpha-liposomes, as evaluated by an aggregometer or a fluorescent microscopy. When ristocetin was added to platelet-rich plasma (PRP) pre-mixed with rhodamine-labeled rGPIbalpha-liposomes, platelets aggregated and rhodamine-fluorescence was strongly positive in the platelet thrombi, suggesting that heterologous aggregation (attachment of liposomes to platelets) occurred. Platelet aggregation in PRP at low platelet concentration (20-80 x 10(6)/ml) was enhanced by rGPIbalpha-liposomes in a dose-dependent manner. Thus, rGPIbalpha-liposomes may accumulate on vWf-exposed subendothelial tissues and enhance platelet function in vivo, supporting hemostasis in thrombocytopenic individuals.
authors.affiliation: Department of Internal Medicine, Keio University School of Medicine, Tokyo, 160-8582, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kitaguchi
authors.forename: M
authors.initials: M
authors.lastname: Murata
authors.forename: K
authors.initials: K
authors.lastname: Iijima
authors.forename: K
authors.initials: K
authors.lastname: Kamide
authors.forename: T
authors.initials: T
authors.lastname: Imagawa
authors.forename: Y
authors.initials: Y
authors.lastname: Ikeda
mesh_terms: D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D006224:Cricetinae; D005434:Flow Cytometry; D006401:Hematologic Agents; D006801:Humans; D008081:Liposomes / Q000008:administration & dosage / Q000737:chemistry*; D010446:Peptide Fragments / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D010974:Platelet Aggregation; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D017713:Platelet Transfusion; D011994:Recombinant Proteins / Q000032:analysis; D012310:Ristocetin / Q000494:pharmacology; D014162:Transfection; D014841:von Willebrand Factor / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D006401:Hematologic Agents; D008081:Liposomes; D010446:Peptide Fragments; D019038:Platelet Glycoprotein GPIb-IX Complex; D011994:Recombinant Proteins; D014841:von Willebrand Factor; D012310:Ristocetin