Fig 4. Endothelial cell forces.
FVEGF is the chemotactic force due to the gradient of VEGF. Fcca and Fccr are the cell-cell adhesive and repulsive forces, respectively. Fd is the drag force associated with the extracellular matrix. The balance between adhesion and repulsion forces acting on the cells is responsible for maintaining the vessel integrity. The chemotactic force acting on the tip cell drives the movement of the tip, which, by the interaction with other cells, guides the remodeling of the vessel. (E = phalanx cell, S = stalk cell, and T = tip cell).