Resolving cell-cell junctions: lumen formation in blood vessels.

Formation of a patent vascular lumen is essential for the transport of oxygen, nutrients and waste products to and from tissues. No matter whether the blood vessel arises from vasculogenesis or angiogenesis, endothelial cells (EC) first have to form a cord, which subsequently lumenizes, in order to generate a functional vessel. During these processes, cellular junctions rearrange between adjacent ECs and are involved in EC polarization as a prerequisite for lumen formation. Here we review the role of EC junctions in vascular lumen formation within different vascular beds.