 To migrate, the endothelial cells need to loosen the endothelial connections by breaking down the basal lamina and the ECM scaffold of blood vessels.These connections are a key determinant of vascular permeability and relieve peri-endothelial cell contact, which is also a major factor in vessel stability and maturity.After the physical barrier is removed, under the influence of the growth factors VEGF with addition contributions of other factors like angiopoietin-1, integrins, and chemokines play an essential role.