FIGURE 5.

Angiogenesis during wound healing. New blood vessel formation is one of the most important stages of wound healing. Endothelial cells at the leading edge or tip branch out or “sprout” to form new capillaries in response to vascular endothelial growth factor (VEGF) and other growth factor signals from epidermal cells, macrophages, and the subcutaneous adipose tissue. The endothelial cells during angiogenesis are leaky to allow for immune cells and other circulating cells to extravasate from the blood vessel lumen into the wound. Pro-angiogenic macrophages release growth factors for endothelial cell growth and fuse newly forming capillaries. Activated endothelial cells upregulate surface markers intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, E-selectin, and P-selectin that help with cell-cell interactions with leukocytes. Deletion of these surface markers during wound healing impairs wound repair. The illustration is a simplified rendering based on current knowledge.