FIGURE 1.

Capillary remodeling by pruning/regression and splitting/duplication. (A) In capillary pruning the poorly perfused vessel is selected to regress, its lumen collapses and the endothelial cells inside (dark orange) polarized against flow and migrate toward the higher flow adjacent vessel. (B) In capillary splitting, highly perfused vessels vasodilate and endothelial cells nearby the intersections (Y bifurcation; dark orange) reorganize their cytoskeleton, migrate toward the lumen and form an intraluminal pillar that will eventually split the vessel forming two daughter vessels. Arrows indicate the direction and intensity of the blood flow (arterial flow in red and venous flow in blue). Endothelial cell nuclei and Golgi are colored in yellow and red, respectively, to show endothelial cell polarization preferentially against the flow.