Figure 5. The trophic role of macrophages in angiogenesis and vascular remodelling.

During eye development, the hyaloid vessel system regresses and is re-patterned. Macrophages closely associated with the vessels synthesize WNT7B, which stimulates vascular endothelial cells to enter the DNA synthesis phase of the cell cycle. In the presence of pericyte-produced angiopoietin 2 (ANG2), the survival signal from ANG1 is blocked and the endothelial cells undergo apoptosis and are phagocytosed by the macrophages. In this manner, vascular regression and proper patterning is achieved^69,70.