Lessons learned from the exquisite design of the endothelial surface glycocalyx and their amazing applications

摘要

In a recent paper by Weinbaum et al. [1], a theoretical model was developed for the structural organization and function of the thin 0.4 μm endothelial surface matrix layer of proteoglycans and glycoproteins that coats the inner lining of our blood vessels. In particular, it is shown that the core proteins in this layer are sufficiently stiff to serve as an exquisitely designed transducer of fluid shear stress to the cortical cytoskeleton of the endothelial cell in initiating intracellular signaling, but offer negligible resistance to buckling when red cell motion is arrested. This latter property allows highly flexible red cells to move through tightly fitting capillaries with remarkably little frictional resistance since the normal force is balanced nearly entirely by the fluid pressure in the highly compressible glycocalyx layer and sliding friction between the cell and the solid phase is vanishingly small. We first show that there is a remarkable dynamic similarity between the motion of red cells gliding on the endothelial glycocalyx and a human snowboarding on fresh powder although they differ in mass by 10~(15). One is able to produce lift forces in each case that are four orders of magnitude larger than classical lubrication theory due to the inability of the trapped fluid or air in the porous layer to rapidly escape. These concepts are then extended to the design of a future generation train that can glide on a track whose permeability and elastic properties are similar to goose down.