Examples of endothelial stem cells in the following topics:
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- New blood vessels are formed from endothelial stem cells, which give rise to the endothelial cells that line the vessels.
- Endothelial stem cells (ESCs) are one of three types of stem cells found in bone marrow.
- ESCs have the characteristic properties of a stem cell: self-renewal and differentiation.
- They give rise to endothelial progenitor cells (EPCs), intermediate stem cells that lose potency.
- Progenitor stem cells are committed to differentiating along a particular cell developmental pathway.
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- Hematopoietic stem cells reside in the bone marrow and have the unique ability to differentiate into all mature blood cell types.
- When they proliferate, at least some of their daughter cells remain as HSCs, so the pool of stem cells does not become depleted.
- As a stem cell matures, it undergoes changes in gene expression that limit the cell types that it can become and move it closer to a specific cell type.
- For the stem cells and other undifferentiated blood cells in the bone marrow, blood cells are determined to specific cell types at random.
- A comprehensive diagram showing the development of different blood cells from hematopoietic stem cell to mature cells.
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- Blood is composed of plasma and three types of cells: red blood cells, white blood cells, and platelets.
- RBCs, endothelial vessel cells, and other blood cells are also marked by glycoproteins that define the different blood types.
- There are several different types of white blood cells: basophils, eosinophils, neutrophils, monocytes, natural killer cells, B- and T-cell lymphocytes, macrophages, and dendritic cells, all of which perform distinct functions.
- They result from fragmentation of large cells called megakaryocytes, which are derived from stem cells in the bone marrow.
- The sticky surface of platelets allows them to accumulate at the site of broken blood vessels to form a clot, due in part to the release of clotting factors that occurs during endothelial injury to blood vessels.
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- Venule walls have three layers: an inner endothelium composed of squamous endothelial cells that act as a membrane, a middle layer of muscle and elastic tissue, and an outer layer of fibrous connective tissue.
- Venules are extremely porous so that fluid and blood cells can move easily from the bloodstream through their walls.
- In contrast to regular venules, high-endothelial venules (HEV) are specialized post-capillary venous swellings.
- They are characterized by plump endothelial cells as opposed to the usual thinner endothelial cells found in regular venules.
- HEVs enable lymphocytes (white blood cells) circulating in the blood to directly enter a lymph node by crossing through the HEV.
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- Platelets, also called thrombocytes, are membrane-bound cell fragments derived from the fragmentation of larger precursor cells called megakaryocytes, which are derived from stem cells in the bone marrow.
- Platelets are not true cells, but are instead classified as cell fragments produced by megakaryocytes.
- They are about 1/10th to 1/20th as abundant as white blood cells.
- They also release wound healing-associated growth factors including platelet-derived growth factor (PDGF), which directs cell movement; TGF beta, which stimulates the deposition of extracellular matrix tissue into a wound during healing; and vascular endothelial growth factor (VEGF), which stimulates angiogenesis, or the regrowth of blood vessels.
- Image from a light microscope (40×) from a peripheral blood smear surrounded by red blood cells.
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- An embryo can be tissue typed to ensure that the embryo implanted can be a cord-blood stem cell donor for a sick sibling.
- Rejection is an adaptive immune response via cellular immunity (mediated by killer T cells inducing apoptosis of target cells) as well as humoral immunity (mediated by activated B cells secreting antibody molecules), though the action is joined by components of innate immune response (phagocytes and soluble immune proteins).
- Highly vascular tissues such as the kidney or the liver often host the earliest signs, particularly at endothelial cells lining blood vessels, though it eventually occurs in roughly 10% to 30% of all kidney transplants, and 50% to 60% of all liver transplants.
- Lysis results in the cell taking up a dye (trypan blue).
- This allows identification of cell's MHC indirectly based on the specificity of the known antibodies in the serum.
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- This is achieved by cell-matrix adhesions through substrate adhesion molecules (SAMs).
- The basement membrane also acts as a mechanical barrier, preventing malignant cells from invading the deeper tissues.
- Basement membrane proteins have been found to accelerate differentiation of endothelial cells.
- A group of diseases stemming from improper function of basement membrane zones are united under the name epidermolysis bullosa (EB).
- It is caused by a mutation in the integrin α6β4 cell-adhesion molecule on either the alpha or beta subunit.
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- Vasculogenesis is the process of blood vessel formation by new production of endothelial cells, in contrast with angiogenesis in which new blood vessels are formed from pre-existing vessels.
- For example, if a monolayer of endothelial cells begins sprouting to form capillaries, angiogenesis is occurring.
- Vasculogenesis occurs when endothelial precursor cells (angioblasts) migrate and differentiate in response to local cues (such as growth factors and extracellular matrix) to form new blood vessels.
- Blood vessel with an erythrocyte (red blood cell) within its lumen, endothelial cells forming its tunica intima or inner layer, and pericytes forming its tunica adventitia (outer layer).
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- Capillaries, which form part of the micro-circulation, are the smallest of the body's blood vessels at between 5-10
μm in diameter with the endothelial vessel wall of only one cell thick.
- During embryological development, new capillaries are formed by vasculogenesis, the process of blood vessel formation occurring by de novo production of endothelial cells and their formation into vascular tubes.
- Continuous - Endothelial cells provide an uninterrupted lining, only allowing small molecules like water and ions to diffuse through tight junctions.
- Fenestrated - Fenestrated capillaries have pores in the endothelial cells (60-80 nanometers in diameter) that are spanned by a diaphragm of radially-oriented fibrils.
- Capillaries are of small diameter with the vessel wall being a single cell thick.
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- Normally, the endothelial cells express molecules that inhibit platelet adherence and activation while platelets circulate through the blood vessels.
- These molecules include nitric oxide, prostacylcine (PGI2) and endothelial ADP-ase.
- During an injury, subendothelial collagen from the extracellular matrix beneath the endothelial cells is exposed on the epithelium as the normal epithelial cells are damaged and removed, which releases von Willebrand Factor (VWF).
- VWF causes the platelets to change form with adhesive filaments (extensions) that adhere to the subendothelial collagen on the endothelial wall.
- PDGF and VEGF are involved in angiogenesis, the growth of new blood vessels and cell cycle proliferation (division) following injury.