Scheme of an angiogenic vessel showing a tip cell responding to a VEGF gradient (blue) and followed by stalk cells of the growing vessel. Yao et al describe the function of Shh for MC recruitment to the stabilizing vessel. The question marks in red highlight pathways with which Shh might interact herein as well as other potential sources and functions of Shh. Ang-1/-2, angiopoietin-1/-2; Dll4, delta-like 4; PDGFRβ, platelet-derived growth factor receptor β; VEGFR2, vascular endothelial growth factor receptor 2; Wnt, Wnt growth factors.