The development of the vascular system begins with the proliferation,coalescence and sprouting of endothelial cells to form a nexus of undifferentiated microvessels. This is remodeled in a poorly understood process to form a network of different-sized vessels. Now, on , Thurston and colleagues show that angiopoietin 1, unlike other vascular growth factors,induces circumferential vessel enlargement without inducing angiogenic sprouting. They report that the treatment of neonatal mice and rats with angiopoietin 1 causes blood vessels to enlarge specifically on the venous side of the circulation. This enlargement, which only occurs during a brief postnatal period, is associated with endothelial cell proliferation. The identification of the molecular factors that regulate vessel plasticity, the researchers suggest, could be crucial for developing new pro- and anti-angiogenic therapies.
