Effects of contact-induced membrane stiffening on platelet adhesion.

The adhesion of platelets plays an essential role in thrombogenesis. Adhesion occurs at sites called focal adhesions (FA), where cell-membrane receptors bind specifically to substrate proteins and couple to each other and to the cytoskeleton via various cellular proteins. The resulting molecular structure suggests that the cortex stiffens at the FA, which likely affects platelet adhesion. This hypothesis is explored by structural analysis and parametric investigation. The cortex is modeled as a shell anchored to the substrate by adhesion forces and subjected to a detachment force. Equilibrium considerations result in a non-linear, two-point boundary value problem that is solved numerically. The results show that cortex stiffening significantly influences the force required for detachment as well as the cell-membrane internal stresses. The magnitude of these effects depends on the ratio of adhesion-to-bending energies and on the inclination of the detachment force. Because the cortex stiffening depends on cellular events, these results suggest a possible mechanism by which platelets can control their adhesion and protect themselves from damage.