Structure and Function of Endothelium - The endothelium is a thin layer of single flat (squamous) cells that line the interior surface of blood vessels and lymphatic vessels. - It forms an interface between circulating blood or lymph and the vessel wall. - Endothelial cells control the flow of substances and fluid into and out of tissues. - They regulate the passage of materials and the transit of white blood cells. - Endothelial cells are involved in blood clotting, inflammation, and the formation of new blood vessels. - They also regulate the constriction and enlargement of blood vessels, controlling blood pressure.

Endothelium and Blood Vessel Formation - The endothelium plays a role in the formation of new blood vessels (angiogenesis). - Angiogenesis is triggered by decreased tissue oxygen or insufficient oxygen tension. - Various signals regulate angiogenesis, including integrins, chemokines, angiopoietins, and oxygen sensing agents. - Angiopoietin-2 works with VEGF to facilitate cell proliferation and migration of endothelial cells. - The general outline of angiogenesis involves activating signals, degradation of the basement membrane, and migration and proliferation of endothelial cells.

Endothelium and Clinical Significance - Endothelial dysfunction is a hallmark for vascular diseases and a key early event in the development of atherosclerosis. - Impaired endothelial function is seen in patients with coronary artery disease, diabetes mellitus, hypertension, hypercholesterolemia, and smokers. - Endothelial dysfunction is predictive of future adverse cardiovascular events and is present in inflammatory diseases. - Changes in endothelial function lead to endothelial dysfunction, characterised by inflammation and activation of endothelial cells. - Endothelial dysfunction promotes accumulation of lipids, inflammation, and the formation of atherosclerotic plaques.

Endothelium in Cancer - Endothelial cells in tumor vasculature have distinct morphological characteristics and molecular signature. - They have a different origin compared to physiological endothelium. - Biomarkers of tumor angiogenesis can be implemented using endothelial cells. - New anti-angiogenic druggable targets can be identified through endothelial cells. - Endothelial cells in tumor vasculature provide an opportunity for new therapeutic interventions.

Endothelium and Diet/Covid-19/Research - A healthy diet abundant in fruits and vegetables improves endothelial function. - A diet high in unhealthy foods adversely affects endothelial function. - Endothelial cells in Covid-19 patients show viral elements and endotheliitis. - Understanding endothelial dysfunction in Covid-19 can help improve patient management. - Endothelial cells can be used in research for studying fibrinolysis and other aspects of endothelial function.