title: The relationship of von Willebrand factor binding to activated platelets from healthy neonates and adults.
abstract: von Willebrand Factor (VWF) is important in platelet adhesion and shear-dependent platelet activation. We performed flow cytometric analyses of VWF binding to and activation of platelets from healthy neonates, children, and adults. Platelets from cord blood (n = 38; gestational age: 36-42 wk; birth weight: 2.4-5.1 kg), neonatal venous blood (n = 19; d 2-3 of life), children (n = 15; age: 1.5-16.3 y), and adults (n = 22; age: 18-55 y) were studied. Binding of VWF was assessed using an antihuman VWF polyclonal antibody and a FITC-conjugated secondary antibody. Platelet activation was determined by the expression of CD62P, CD63, CD41, CD42b, activated GPIIb/IIIa (PAC-1), procoagulant surface (as reflected by annexin V binding), and microparticle formation. Although the mean percentage of VWF-positive platelets was not significantly higher in unstimulated platelets from 2- to 3-d-old neonates, their platelets were more activated than those from adults, and there was a positive correlation of VWF binding with platelet activation (CD62P: r = 0.74, p < 0.001; annexin V: r = 0.46, p < 0.05). In adults, after in vitro activation of platelets with thrombin and ADP, VWF binding to platelets increased and correlated significantly with CD62P expression (r = 0.71, p < 0.001). VWF binding to unstimulated neonatal platelets was, however, higher than that to in vitro-stimulated platelets from adults at the same level of expression of platelet activation markers. Further studies are required to assess the mechanism and significance of VWF binding to activated platelets in the neonatal period.
authors.affiliation: Division of Haematology/Oncology, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8.
authors.forename: Markus
authors.initials: M
authors.lastname: Schmugge
authors.forename: Margaret Lucille
authors.initials: ML
authors.lastname: Rand
authors.forename: Kyong Won Annie
authors.initials: KW
authors.lastname: Bang
authors.forename: Meera
authors.initials: M
authors.lastname: Mody
authors.forename: Michael Stephen
authors.initials: MS
authors.lastname: Dunn
authors.forename: Kofi Sarpong
authors.initials: KS
authors.lastname: Amankwah
authors.forename: Victor Stanley
authors.initials: VS
authors.lastname: Blanchette
authors.forename: John
authors.initials: J
authors.lastname: Freedman
mesh_terms: D000293:Adolescent; D000328:Adult; D001792:Blood Platelets / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D019007:P-Selectin / Q000378:metabolism; D015539:Platelet Activation; D011485:Protein Binding; D013223:Statistics as Topic; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D019007:P-Selectin; D014841:von Willebrand Factor