ECs require support from surrounding cells such as pericytes, podocytes, and smooth muscle cells [63] . These cells actively control vascular behaviour by producing signalling compounds (for instance, Ang-1 and VEGF) that govern the activity and response of ECs [61] . To attract ECs, Ang-1 secreted by support cells binds to the extracellular matrix. In quiescent ECs, this binding results in Tie2 movement to the site of cell-cell interaction. In mobile ECs, Ang-1 polarizes the cell with Tie2 movement abluminal site [65] . In tumour angiogenesis and in inflammation, Ang-2 recruits Tie2positive monocytes and causes them to release cytokines and adopt a pro-angiogenic phenotype [111] .