Figure 2

Illustrations of cell movement represented by rules in the model. For clarity, movement is shown in two-dimensions. The tip cell is represented by a red node and segment; the node shared between the tip and stalk cells is yellow; and the blue node and segment is the adjacent stalk cell segment. Black segments and nodes represent quiescent vessels. Arrows represent direction of movement for nodes. (A) Schematic of a capillary with an activated tip cell. (B) Movement when there is no growth factor gradient. (C) Movement and the resulting cell segment positions when there is a VEGF gradient, and the effects of allowed stalk cell elongation. (D) Results when there is only elongation of the stalk cell occurring, and no additional migration of the tip cell. (E) Results when there is proliferation of the stalk cells.