Figure 1.

Experimental observations of lumen formation. (a) Time-lapse images of endothelial cells (ECs) in a three-dimensional collagen gel, showing formation of vacuoles into larger intracellular compartments. (Adapted from Kamei et al. [3].) (b) Two-photon time-lapse imaging of an ISV in which membranes are labelled with EGFP-cdc42wt and intravascularly injected red quantum dots are serially transferred by vacuole fusion. (Adapted from Kamei et al. [3].) (c) Lumens form during in vitro three-dimensional angiogenic sprouting assays by cell–cell repulsion facilitated by negatively charged CD34-sialomucins (control panel). Cleavage (neuraminidase panel) or neutralization (protamine sulfate panel) hereof reduces lumen formation. (Adapted from Strilic et al. [5].)