Significant differences in single-platelet biophysics exist across species but attenuate during clot formation.

Clotting is an inherently mechanical process, as demonstrated by recent studies showing that biophysical parameters, such as platelet margination,1 thrombus porosity,2 shear forces,3 compression forces,4 and single-platelet forces,5 affect hemostasis and may be pathologically altered in disease states.6 However, little is known about the most basic biophysical differences between platelets of various animal species, especially dogs, mice, pigs, and sheep, that are commonly used as models for investigations into hemostasis and thrombosis because of their anatomical similarity to human blood vessels, organs, and cellular physiology. This lack of biophysical information hinders our interpretation of the animal models that have been used for various antiplatelet and anticoagulant therapeutic discoveries, including clopidogrel and bivalirudin,7 and models of various disease states, such as heart failure,8 trauma,9 hemophilia,10 and Glanzmann’s thrombasthenia.11,12 To address this knowledge gap, we leveraged characterized and novel biophysical assays, to map out and define a biophysical signature for the platelets of each species. These biophysical assays have shown the influence of cytoskeletal signaling pathways on the behavior of platelets, specifically the myosin light chain kinase13 and ρ-associated protein kinase5 pathways. Our study specifically focused on understanding the differences in platelet adhesion on collagen and fibrinogen, spreading area, single-platelet contraction forces, and volumetric bulk clot contraction, all of which may influence the initiation, propagation, and stability of blood clots. As the first study, to our knowledge, to comprehensively investigate interspecies biophysical differences, our work complements the existing literature that has demonstrated that platelet aggregation,14 coagulation,15 and dense granules16 differ among various animal species. Our new data help provide a rich picture of the interspecies biophysical differences that inform findings from various animal models of hemostasis.