title: Activated platelet-derived microparticles in thalassaemia.
abstract: Thromboembolic complications have been documented in thalassaemia patients. The aggregability of abnormal red blood cells and the high level of membrane-derived microparticles (MPs) stemming from blood cells are thought to be responsible for the associated thrombotic risk. We investigated the number of MPs, their cellular origin and their procoagulant properties in beta-thalassaemia. Fresh whole blood was simultaneously stained for annexin V, cellular antigens and the known density beads. The procoagulant properties of these phosphatidylserine (PS)-bearing MPs were also measured by assessing the platelet factor-3-like activity in the blood. Flow cytometric results showed that splenectomised beta-thalassaemia/HbE patients had significantly higher levels of PS-bearing MPs than non-splenectomised beta-thalassaemia/HbE patients and normal individuals (P < 0.0001). There was a good correlation between PS-bearing MPs and PS-bearing platelets, reflecting the existence of chronic platelet activation in beta-thalassaemia/HbE patients (r(s) = 0.511, P < 0.001). The cellular origin of PS-bearing MPs showed mostly activated-platelet origin with adhesion (CD41a/CD62P/CD36). Moreover, the platelet procoagulant activity was higher in splenectomised beta-thalassaemia/HbE patients when compared with non-splenectomised (P < 0.05) and normal individuals (P < 0.01), and the amount correlated with PS-bearing MPs (rs = 0.560, P < 0.001). These findings suggest that MPs originate from activated platelets with a potential to aggravate thrombotic events when the numbers are excessive, as is commonly seen in splenectomised beta-thalassaemia/HbE patients.
authors.affiliation: Centre of Excellence for Flow Cytometry, Office for Research and Development, Department of Immunology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok. grkpy@mahidol.ac.th
authors.forename: Kovit
authors.initials: K
authors.lastname: Pattanapanyasat
authors.forename: Siriphan
authors.initials: S
authors.lastname: Gonwong
authors.forename: Porntip
authors.initials: P
authors.lastname: Chaichompoo
authors.forename: Egarit
authors.initials: E
authors.lastname: Noulsri
authors.forename: Surada
authors.initials: S
authors.lastname: Lerdwana
authors.forename: Kasama
authors.initials: K
authors.lastname: Sukapirom
authors.forename: Noppadol
authors.initials: N
authors.lastname: Siritanaratkul
authors.forename: Suthat
authors.initials: S
authors.lastname: Fucharoen
mesh_terms: D000293:Adolescent; D000328:Adult; D017304:Annexin A5 / Q000097:blood; D001777:Blood Coagulation; D001792:Blood Platelets / Q000378:metabolism; D016022:Case-Control Studies; D004910:Erythrocyte Membrane; D005434:Flow Cytometry; D006801:Humans; D010718:Phosphatidylserines / Q000378:metabolism; D015539:Platelet Activation; D010976:Platelet Count; D010977:Platelet Factor 3 / Q000032:analysis; D013156:Splenectomy; D018709:Statistics, Nonparametric; D017086:beta-Thalassemia / Q000097:blood* / Q000378:metabolism
chemical_list: D017304:Annexin A5; D010718:Phosphatidylserines; D010977:Platelet Factor 3