Fig. 4. Saturating VEGF-A gradients inhibits capillary network formation. (A and B) Human ECs from cord veins were plated (125 cells/mm²) on Matrigel in the absence (A) or presence (B) of a saturating amount of VEGF-A₁₆₅ (20 nM). Capillary-like network formation was recorded after 3 h and it is evident that saturating VEGF-A inhibits the first step of capillary-like formations, where ECs start moving toward their neighbors to eventually adhere and form a continuous multicellular network. Heat-inactivated VEGF-A₁₆₅ was inactive and did not allow capillary network formation (not shown). (C and D) Cell organization patterns obtained by simulating Model (1–3) using the same number of ECs as in panels A and B in the presence (C) or absence (D) of the chemoattractant mechanism. Compared with the control condition (C), simulated extinction of chemoattractant gradients (D) resulted in an inhibition of pattern formation similar to that obtained by extinguishing them experimentally.