Angiogenesis, lymphangiogenesis and atopic dermatitis.

Angiogenesis and morphological and functional alterations of microvessels are hallmark features of chronic inflammatory disorders, including certain skin diseases. Vascular endothelial growth factors (VEGFs) are key regulators of blood vessel growth. The VEGF family includes VEGF-A, -B, -C, -D and placental growth factor. VEGF-A and -B are the most important proangiogenic factors, while VEGF-C and -D primarily regulate lymphangiogenesis. Angiopoietins are promoters of neovascularization by interacting with Tie-1 and Tie-2 receptors present on endothelial cells. High levels of VEGF-A have been detected in skin tissue of atopic dermatitis (AD) patients and correlate with disease activity. The vascular changes in the skin of AD patients appear to be linked to the inflammatory process. Effector cells of skin inflammation (human mast cells, basophils, eosinophils, macrophages, lymphocytes, etc.) are major sources of a vast array of angiogenic and lymphangiogenic factors. The role of lymphangiogenesis in AD is largely unknown.