Vascular and Capillary Endothelium
The endothelium is a monolayer of cells that line the inner lumen of all blood vessels. Endothelial cells respond to both mechanical forces created by blood flow and stimulatory molecules within the blood by producing vasoactive molecules that control vessel tone, thrombosis, and leukocyte adhesion. The healthy endothelium creates a nonthrombogenic surface, but when stimulated by injury, endothelial cells can produce cytokine or chemokine activators of the coagulation cascade or an inflammatory response. Vascular diseases such as atherosclerosis, diabetes, and sickle cell disease involve alterations of the function of the endothelium in which the cells promote vasoconstriction and a prothrombotic and proinflammatory state. While endothelial cells have the capacity to proliferate, endothelial progenitor cells derived from bone marrow and circulating in blood have the potential to regenerate injured regions of endothelium. These progenitor cells provide a new source of endothelium that may delay the onset of atherosclerosis and be used to generate new blood vessels.
