Fig. 4

Overview of angiogenesis and rationale for biomarker selection in the current study. A Ischaemic insult results in the secretion of VEGF from hypoxic cells (shown in dark red). VEGF signaling stimulates the transformation of a resting vascular endothelial cell into a tip cell. B The tip cell guides the migration of a vascular stalk towards the area of high VEGF concentration, facilitated by the secretion of basement-degrading enzymes such as MMP-9. C Ligation of endothelial cell-expressed Tie-2 by angpt-1 exerts anti-apoptotic, anti-inflammatory and pro-migratory effects, and promotes tight junction formation between neighbouring cells to reduce vascular permeability. D Angpt-2 competes for the Tie-2 receptor to antagonise angpt-1 mediated processes