endothelialcell

Endothelial cells are a type of squamous cell that line the interior surface of all blood vessels and lymphatic vessels, forming the endothelium. They form a continuous monolayer that interfaces with circulating blood and interstitial tissue. Endothelial cells vary in morphology and function across the vascular tree, with continuous, fenestrated, and sinusoidal phenotypes in different tissues; arterial, venous, and microvascular endothelia also show specialization. Lymphatic endothelial cells line lymphatic vessels and possess distinct markers and junctions.

Key features include a glycocalyx on the luminal surface, gap junctions, and adherens junctions such as VE-cadherin, which regulate permeability and cell cohesion. Weibel-Palade bodies store von Willebrand factor and other molecules involved in hemostasis and inflammation.

Endothelial cells regulate vascular tone by producing vasodilators such as nitric oxide and prostacyclin, and vasoconstrictors such as endothelin-1. They control blood fluidity and coagulation, balancing anti-thrombotic and pro-thrombotic states. They regulate permeability to solutes and fluid, respond to shear stress, and mediate leukocyte adhesion and diapedesis through adhesion molecules like ICAM-1 and VCAM-1. They participate in angiogenesis and remodeling in development, wound healing, and cancer, under VEGF, Notch, and PDGF signaling.

Endothelial dysfunction refers to impaired vasodilation, a pro-inflammatory, pro-thrombotic state, and increased permeability. It is associated with aging, hypertension, diabetes, hyperlipidemia, and smoking and underlies cardiovascular diseases such as atherosclerosis and edema. Dysfunction can involve reduced nitric oxide bioavailability and glycocalyx degradation.

Replacement and repair: Endothelial cells are replenished by local proliferation and circulating endothelial progenitor cells; they migrate to sites of injury. In research, cultured endothelial cells are used to study vascular biology, and in tissue engineering and organ-on-a-chip models to replicate vascular interfaces.