Platelets and physics: How platelets "feel" and respond to their mechanical microenvironment.

During clot formation, platelets are subjected to various different signals and cues as they dynamically interact with extracellular matrix proteins such as von Willebrand factor (vWF), fibrin(ogen) and collagen. While the downstream signaling of platelet-ligand interactions is well-characterized, biophysical cues, such as hydrodynamic forces and mechanical stiffness of the underlying substrate, also mediate these interactions and affect the binding kinetics of platelets to these proteins. Recent studies have observed that, similar to nucleated cells, platelets mechanosense their microenvironment and exhibit dynamic physiologic responses to biophysical cues. This review discusses how platelet mechanosensing is affected by the hydrodynamic forces that dictate vWF-platelet interactions and fibrin polymerization and network formation. The similarities and differences in mechanosensing between platelets and nucleated cells and integrin-mediated platelet mechanosensing on both fibrin(ogen) and collagen are then reviewed. Further studies investigating how platelets interact with the mechanical microenvironment will improve our overall understanding of the hemostatic process.