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Platelet transfusion for patients with platelet dysfunction: effectiveness, mechanisms, and unanswered questions. Curr Opin Hematol 2021; 27:378-385. [PMID: 32868672 DOI: 10.1097/moh.0000000000000608] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
PURPOSE OF REVIEW In this review, we discuss current clinical guidelines and potential underlying mechanisms regarding platelet transfusion therapy in patients at risk of bleeding, comparing management of patients with thrombocytopenia versus those with qualitative platelet disorders. RECENT FINDINGS Platelet transfusion therapy is highly effective in managing bleeding in patients with hypoproliferative thrombocytopenia. Clinical trials have demonstrated that platelet transfusion can be used at a lower trigger threshold and reduced platelet doses, and may be used therapeutically rather than prophylactically in some situations, although additional data are needed. In patients with inherited platelet disorders such as Glanzmann's Thrombasthenia or those with RASGRP2 mutations, platelet transfusion may be ineffective because of competition between transfused and endogenous platelets at the site of vascular injury. Successful management of these patients may require transfusion of additional platelet units, or mechanism-driven combination therapy with other pro-hemostatic agents. In patients on antiplatelet therapy, timing of transfusion and inhibitor mechanism-of-action are key in determining therapeutic success. SUMMARY Expanding our understanding of the mechanisms by which transfused platelets exert their pro-hemostatic function in various bleeding disorders will improve the appropriate use of platelet transfusion.
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Canault M, Alessi MC. RasGRP2 Structure, Function and Genetic Variants in Platelet Pathophysiology. Int J Mol Sci 2020; 21:E1075. [PMID: 32041177 PMCID: PMC7037602 DOI: 10.3390/ijms21031075] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 01/31/2020] [Accepted: 02/03/2020] [Indexed: 12/18/2022] Open
Abstract
RasGRP2 is calcium and diacylglycerol-regulated guanine nucleotide exchange factor I that activates Rap1, which is an essential signaling-knot in "inside-out" αIIbβ3 integrin activation in platelets. Inherited platelet function disorder caused by variants of RASGRP2 represents a new congenital bleeding disorder referred to as platelet-type bleeding disorder-18 (BDPLT18). We review here the structure of RasGRP2 and its functions in the pathophysiology of platelets and of the other cellular types that express it. We will also examine the different pathogenic variants reported so far as well as strategies for the diagnosis and management of patients with BDPLT18.
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Affiliation(s)
- Matthias Canault
- Aix Marseille University, INSERM, INRAE, C2VN, 13005 Marseille, France
| | - Marie-Christine Alessi
- Aix Marseille University, INSERM, INRAE, C2VN, 13005 Marseille, France
- Hematology laboratory, APHM, CHU Timone, 13005 Marseille, France
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Lee RH, Piatt R, Dhenge A, Lozano ML, Palma-Barqueros V, Rivera J, Bergmeier W. Impaired hemostatic activity of healthy transfused platelets in inherited and acquired platelet disorders: Mechanisms and implications. Sci Transl Med 2019; 11:eaay0203. [PMID: 31826978 PMCID: PMC10824274 DOI: 10.1126/scitranslmed.aay0203] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 10/11/2019] [Indexed: 12/21/2022]
Abstract
Platelet transfusions can fail to prevent bleeding in patients with inherited platelet function disorders (IPDs), such as Glanzmann's thrombasthenia (GT; integrin αIIbβ3 dysfunction), Bernard-Soulier syndrome [BSS; glycoprotein (GP) Ib/V/IX dysfunction], and the more recently identified nonsyndromic RASGRP2 variants. Here, we used IPD mouse models and real-time imaging of hemostatic plug formation to investigate whether dysfunctional platelets impair the hemostatic function of healthy donor [wild-type (WT)] platelets. In Rasgrp2-/- mice or mice with platelet-specific deficiency in the integrin adaptor protein TALIN1 ("GT-like"), WT platelet transfusion was ineffective unless the ratio between mutant and WT platelets was ~2:1. In contrast, thrombocytopenic mice or mice lacking the extracellular domain of GPIbα ("BSS-like") required very few transfused WT platelets to normalize hemostasis. Both Rasgrp2-/- and GT-like, but not BSS-like, platelets effectively localized to the injury site. Mechanistic studies identified at least two mechanisms of interference by dysfunctional platelets in IPDs: (i) delayed adhesion of WT donor platelets due to reduced access to GPIbα ligands exposed at sites of vascular injury and (ii) impaired consolidation of the hemostatic plug. We also investigated the hemostatic activity of transfused platelets in the setting of dual antiplatelet therapy (DAPT), an acquired platelet function disorder (APD). "DAPT" platelets did not prolong the time to initial hemostasis, but plugs were unstable and frequent rebleeding was observed. Thus, we propose that the endogenous platelet count and the ratio of transfused versus endogenous platelets should be considered when treating select IPD and APD patients with platelet transfusions.
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Affiliation(s)
- Robert H Lee
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA.
- UNC Blood Research Center, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Raymond Piatt
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Ankita Dhenge
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA
- UNC Blood Research Center, University of North Carolina, Chapel Hill, NC 27599, USA
| | - María L Lozano
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Arrixaca, CB15/00055-CIBERER, Murcia 30003, Spain
| | - Verónica Palma-Barqueros
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Arrixaca, CB15/00055-CIBERER, Murcia 30003, Spain
| | - José Rivera
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Arrixaca, CB15/00055-CIBERER, Murcia 30003, Spain
| | - Wolfgang Bergmeier
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA.
- UNC Blood Research Center, University of North Carolina, Chapel Hill, NC 27599, USA
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Yun JW, Lee KO, Jung CW, Oh SY, Kim SH, Choi CW, Kim HJ. Hereditary platelet function disorder from RASGRP2 gene mutations encoding CalDAG-GEFI identified by whole-exome sequencing in a Korean woman with severe bleeding. Haematologica 2019; 104:e274-e276. [PMID: 30846498 DOI: 10.3324/haematol.2019.218487] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- Jae Won Yun
- Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul
| | - Ki-O Lee
- Samsung Biomedical Research Institute, Samsung Medical Center
| | - Chul Won Jung
- Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine
| | - Soo-Young Oh
- Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine
| | - Sun-Hee Kim
- Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul
| | - Chul Won Choi
- Division of Hematology and Oncology, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea
| | - Hee-Jin Kim
- Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul
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A mutation of the human EPHB2 gene leads to a major platelet functional defect. Blood 2018; 132:2067-2077. [PMID: 30213874 DOI: 10.1182/blood-2018-04-845644] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 09/08/2018] [Indexed: 12/14/2022] Open
Abstract
The ephrin transmembrane receptor family of tyrosine kinases is involved in platelet function. We report the first EPHB2 variant affecting platelets in 2 siblings (P1 and P2) from a consanguineous family with recurrent bleeding and normal platelet counts. Whole-exome sequencing identified a c.2233C>T variant (missense p.R745C) of the EPHB2 gene. P1 and P2 were homozygous for this variant, while their asymptomatic parents were heterozygous. The p.R745C variant within the tyrosine kinase domain was associated with defects in platelet aggregation, αIIbβ3 activation, and granule secretion induced by G-protein-coupled receptor (GPCR) agonists and convulxin, as well as in thrombus formation on collagen under flow. In contrast, clot retraction, flow-dependent platelet adhesion, and spreading on fibrinogen were only mildly affected, indicating limited effects on αIIbβ3 outside-in signaling. Most importantly, Lyn, Syk, and FcRγ phosphorylation, the initial steps in glycoprotein VI (GPVI) platelet signaling were drastically impaired in the absence of platelet-platelet contact, indicating a positive role for EPHB2 in GPVI activation. Likewise platelet activation by PAR4-AP showed defective Src activation, as opposed to normal protein kinase C activity and Ca2+ mobilization. Overexpression of wild-type and R745C EPHB2 variant in RBL-2H3 (rat basophilic leukemia) cells stably expressing human GPVI confirmed that EPHB2 R745C mutation impaired EPHB2 autophosphorylation but had no effect on ephrin ligand-induced EPHB2 clustering, suggesting it did not interfere with EPHB2-ephrin-mediated cell-to-cell contact. In conclusion, this novel inherited platelet disorder affecting EPHB2 demonstrates this tyrosine kinase receptor plays an important role in platelet function through crosstalk with GPVI and GPCR signaling.
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