Although the primary function of blood vessels is to provide organs with the oxygen and nutrients that are essential for tissue growth and maintenance, blood vessels also provide positive paracrine signals during early pancreas development. Now, Yuval Dor and colleagues report that, surprisingly, non-nutritional signals from blood vessels restrain pancreas growth later in development (see ). In gain-of-function experiments, they show that VEGF-induced hypervascularisation restrains pancreatic growth in embryonic mice. Conversely, the elimination of endothelial cells increases the size of embryonic pancreatic buds. Blood vessels, they report, restrict the formation of pancreatic tip cells, reduce pancreatic lateral branching and prevent differentiation of the pancreatic epithelium into endocrine and exocrine cells both in vivo and ex vivo. The researchers propose, therefore, that the vasculature controls pancreas morphogenesis and growth by reducing branching and by maintaining the undifferentiated state of primitive epithelial cells. These unexpected findings might have important implications for the derivation of insulin-producing β-cells from embryonic stem cells for the treatment of diabetes.
