Figure 2.

Angiogenic sprouting and blood vessel growth. ECs initiate sprouting in response to tissue-derived signals such as VEGF. A fraction of cells (shown in yellow and green) extends long filopodia and acquires motile and invasive behavior. These tip cells lead and guide new sprouts, whereas other ECs (shown in red) form the sprout stalk or stay behind to maintain tissue perfusion. At some point during sprout extension, tip cells will contact other tip cells or vessels to establish new connections. These cell bridges (orange) are converted into new blood-carrying vessels. Simultaneously, new sprouting is initiated at other sites (yellow and green cells) and additional ECs are generated by proliferation (purple).