Meta-Environment No6: The endothelium is a monolayer interface integrating hemodynamics, metabolism, and systemic inflammation

The endothelium has long been considered in anatomy as a passive monolayer lining the inner surface of blood and lymphatic vessels - nothing more than the "wallpaper" of the vascular system. However, over the past decade, data have accumulated that require a fundamental revision of this view. The endothelium is an active, dynamic, distributed system throughout the vascular bed that regulates vascular tone, permeability, hemostasis, immune surveillance, and angiogenesis. We substantiate that the endothelium is not just a cell layer, but an active meta-medium No6 that meets all four criteria of the meta-environment. The endothelium functions as a central sensor and regulator of hemodynamic, metabolic, and inflammatory signals. Its dysfunction is characterized by decreased nitric oxide (NO) bioavailability, increased oxidative stress, chronic low-intensity inflammation, and accumulation of senescent endothelial cells secreting pro-inflammatory mediators. These changes are the basis of hypertension, atherosclerosis, heart failure and other cardiovascular diseases. Particular attention is paid to the systemic restoration of the endothelium within the framework of the Quatotron technique - a multimodal physical effect aimed at restoring endothelial function and glycocalyx, reducing inflammation and oxidative stress, as well as rejuvenating the vascular bed. Understanding the endothelium as a meta-environment opens up new opportunities for the prevention and treatment of cardiovascular diseases, age-related vascular stiffness and systemic inflammation.