Abstract
BACKGROUND: Patients with pathogenic variants in RASGRP2 (inherited platelet disorder (IPD)-18) exhibit normal platelet counts but impaired platelet aggregation and α(IIb)β(3) activation. Moderate-to-severe bleeding episodes require patients to be transfused with platelets and/or pro-hemostatic agents. We recently demonstrated that hemostatic efficacy of transfused platelets is limited by dysfunctional endogenous platelets in a mouse model of IPD-18 (Rasgrp2(-/-) mice), as dysfunctional platelets were recruited to the forming hemostatic plug but did not participate in clot contraction. Thus, higher amounts of transfused platelets were required to outcompete these dysfunctional cells and to reverse bleeding. OBJECTIVE: We here studied the usefulness of thromboelastography with platelet mapping (TEG-PM) for ex vivo monitoring of the hemostatic potential in Rasgrp2(-/-) mice transfused with various amounts of wild-type (WT) platelets. METHODS: Whole blood (WB) samples from WT and Rasgrp2(-/-) mice were tested in TEG-PM and parameters for clot formation and contraction (K time, α-angle, maximum amplitude [MA]) were measured. RESULTS: Rasgrp2(-/-) WB samples did not contract in TEG-PM, consistent with a critical role of this protein in α(IIb)β(3) activation. Addition of WT platelets improved TEG parameters in a ratio-dependent manner, consistent with our recent in vivo studies showing impaired hemostasis at a 5:1, but not at a 2:1 ratio of mutant to WT platelets. K and α values were identified as better predictors of transfusion efficacy than MA, the most platelet-dependent TEG parameter. CONCLUSION: This proof-of-concept study supports the use of TEG-PM to monitor platelet transfusion ratios and hemostatic potential in IPD-18 and potentially other platelet disorders.