Endothelial cells are a thin layer of specialized epithelial cells, consisting of a layer of flat cells, which are polygonal in shape, and the edges of the cells are sawtooth-shaped and chimeric. It forms the inner wall of the blood vessel and is the interface between the blood in the lumen of the blood vessel and other blood vessel walls (monolayer squamous epithelium).
Figure 1. The figure shows the location of endothelial cells
Endothelial cells or vascular endothelium are a thin layer of specialized epithelial cells, consisting of a layer of flat cells, which are polygonal in shape, and the edges of the cells are sawtooth-shaped and chimeric. It forms the inner wall of the blood vessel and is the interface between the blood in the lumen of the blood vessel and other blood vessel walls (monolayer squamous epithelium). Endothelial cells are along the entire circulatory system, from the heart to the smallest microvessels. Endothelial cells on the ventricular surface are called endocardium. Microvessels and lymphatic microtubules are composed of a single layer of endothelial cells. Endothelial tissue is a special kind of epithelial tissue, and epithelial tissue is one of the four biological tissues of animals.
Figure 2. Transmission electron micrographs of microvessels show that endothelial cells surround red blood cells (E), forming the innermost layer of the blood vessels, the intima.
Vascular endothelial cells (EC) are located between plasma and vascular tissues. It can not only complete the metabolic exchange of plasma and interstitial fluid, but also synthesize and secrete a variety of biologically active substances to ensure the normal contraction and relaxation of blood vessels and maintain vascular tension. , Regulate blood pressure and coagulation and anticoagulation balance and other special functions, so as to maintain normal blood flow and long-term patency of blood vessels. Endothelialization of the surface of anticoagulant materials can reduce thrombus formation and platelet activation.
Figure 3. Endothelial lining on inner wall of blood vessel.
Intact endothelialization is the best anticoagulant, and the surface vascular endothelial tissue is the natural anticoagulant tissue. Endothelial cell membranes have natural anticoagulant components such as heparin, prostaglandin (PGI), nitric oxide, etc. Endothelial cells can synthesize and secrete a variety of endothelium-derived relaxing factors. Endothelial cells are involved in multiple vascular biology categories, including vasoconstriction and vasodilation to control blood pressure; coagulation, anticoagulation and fibrinolysis (thrombosis and fibrinolysis); arteriosclerosis; angiogenesis; inflammation and swelling (edema). Endothelial cells also control certain substances, such as white blood cells entering and leaving blood vessels. In some organs, there are highly differentiated endothelial cells responsible for special filtering functions. Examples include glomeruli and cerebrovascular barriers.
Endothelial protein C receptor
Endothelin C receptor (EPCR) is a protein encoded by the PROCR gene in humans. PROCR has also recently been designated as CD201 (differentiated cluster 201). The protein encoded by this gene is a receptor for protein C that enhances its activation. Protein C is an anticoagulant serine protease activated by the blood coagulation pathway. EPCR protein is an N-glycosylated type I membrane protein that enhances protein C activation. It belongs to the MHC I/CD1 class protein family, which is characterized by deep grooves. Other proteins in this family (not in EPCR) are often used for antigen binding. Like CD1 series, EPCR also has lipids in the corresponding grooves. The lipid bound in EPCR is usually phosphatidylcholine, which may also be phosphatidylethanolamine. Although it may not be in direct contact, it helps protein C binding.
Figure 4. Protein structure of Endothelin C receptor (EPCR).
1. Rothbarth K.; et al. One single mRNA encodes the centrosomal protein CCD41 and the endothelial cell protein C receptor (EPCR). FEBS Lett. 1999, 458 (1): 77–80.