Hormones and Antiaging Medicine: Endothelial Cells as Endocrine Cells

Maintaining the morphology of the circulatory system and its normal functioning is the most basic and essential for life support. The length of blood vessels extends to about 100,000 km in total, and except for a few exceptions such as the cornea and epithelium, they are distributed in all parts of the body, and like tree branches, make nonoverlapping branches to enjoy sunlight and blood vessels are spread out so that oxygen and nutrients can be supplied to peripheral tissues without excess or deficiency. Therefore, as can be easily imagined from the famous quote by Dr. William Osler (1849–1919), “Humans age with blood vessels;” the failure of the vascular system as a route for oxygen and nutrient supply leads to organ aging, which appears as changes and failures in various tissue functions. Endothelial cells, which exist as the innermost layer of cells on the inner side of the vascular lumen anatomically, produce and secrete various physiologically active factors such as nitric oxide (NO) and endothelin and play an important role in maintaining the homeostasis of vascular functions such as contraction and relaxation (dilation) regulation, inflammation and permeability regulation, and coagulation and fibrinolytic system regulation. The total area covered by endothelial cells is 7000 km2, the total weight is 1 kg, and it is the largest endocrine organ in the human body, and its dysfunction is the basis of various brain and cardiovascular diseases whose onset risk increases with age.