Angiogenesis is dependent on multiple growth factors and receptors and their signalling systems and transcriptional regulators [101] . The process is complex and encompasses the recruitment of mobile ECs and endothelial progenitor cells, the proliferation and apoptosis of these cells, and reorganization of the surroundings [102] . To form stable new blood vessels, the response must be coordinated in time and space, and the Ang/Tie system is involved from beginning to end. To prepare for angiogenesis, Ang-2 destabilizes quiescent endothelium through an internal autocrine loop mechanism [44, 103] . Before vascular sprouting starts, focal adhesion kinase and proteinases such as plasmin and metalloproteinases are excreted [85] . Often, this stage is preceded by activation of innate immunity and inflammation [104] . Apparently, the machinery to clean up after the work has been finished is installed before the work is commenced, again illustrating the close relations among the different processes [104] .