Angiogenezis

Angiogenezis, or angiogenesis, is the growth of new blood vessels from existing ones. It is essential for development and tissue repair, and it also contributes to pathological conditions when dysregulated.

The process begins with an angiogenic switch and endothelial activation by factors such as vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF). Endothelial cells secrete enzymes to degrade the basement membrane, migrate as tip cells toward the stimulus, and proliferate as stalk cells to extend nascent vessels. Lumen formation and stabilization follow, aided by pericytes and smooth muscle cells.

Two main modes exist: sprouting angiogenesis (new vessels sprout from existing ones) and intussusceptive angiogenesis (vessels split). Regulation depends on a balance between pro-angiogenic and anti-angiogenic signals, with Notch signaling, angiopoietins, and other pathways shaping vessel patterning and maturation.

Physiological roles include embryonic development, wound healing, the female reproductive cycle, and placental formation. Pathological angiogenesis underlies cancer growth, diabetic retinopathy, age-related macular degeneration, psoriasis, and chronic inflammation, illustrating the consequences of dysregulated vessel formation.

Clinical implications include anti-angiogenic therapies, such as VEGF inhibitors, used to slow tumor growth and treat certain eye diseases; and experimental pro-angiogenic approaches to improve perfusion after ischemic injury. Research in angiogenesis has evolved since the concept was proposed in the 1970s, with the identification of VEGF and other regulatory pathways that shape vessel growth and stability.