Platelets pull: how thrombin drives contractility

In this issue of Blood Advances, Hiebner et al1 report that thrombin stimulation boosts single-platelet contractility by 50% compared to stimulation with other agonists. Additionally, the authors show that high thrombin concentrations can overcome the inhibition of clot contraction by antiplatelet drugs.Platelets contract, generating forces that stabilize a primary hemostatic plug and compact a fibrin clot. Prior work has demonstrated that impaired platelet contractility is associated with hemostatic dysfunction, including increased bleeding symptoms,2 thrombus embolization,3 and need for transfusion in trauma victims.4 Platelet contractility can be measured on the multicellular scale with clot retraction and on the single-platelet scale with traction force microscopy.