Fig. 3. VEGF signaling during bone regeneration. VEGF stimulates the formation of newblood vessel,which can bring progenitor cells for bone formation to the fracture callus. In addition,
VEGF upregulates the expression of osteogenic growth factors in endothelial cells, mediating osteoblast differentiation. Lastly, VEGFmight also directly affect osteoblast behavior including
differentiation, proliferation and chemotaxis.