Vascular Modulatory Functions of Macrophages

Monocytes/macrophages have long been regarded as important regulators of angiogenesis and vascular remodeling in both developmental and pathological processes. Historically, the ability of macrophages to promote vascular growth has been primarily attributed to their secretion of proangiogenic growth factors, like VEGFA, and matrix-remodeling enzymes, like metallo-proteinases. Recent studies have also suggested that physical contacts with endothelial cells are important to mediate some of the vascular modulatory functions of macrophages. In this review, we provide an account of the cellular and molecular mechanisms that underlie the involvement of macrophages in the regulation of vascular development and growth during angiogenesis, arteriogenesis, and lymphangiogenesis. Furthermore, we discuss the prospect of either inhibiting or enhancing the vascular modulatory functions of macrophages in disease conditions characterized by either excessive or insufficient tissue vascularization