Endothelial Stem Cells
Endothelial stem cells are those which give rise to endothelial cells which line the interior surface of blood vessels. These cells are specialized in that they are the interface between the circulating blood and the blood vessel wall and it is their responsibility, to a large extent, to ensure that the blood flows freely. Endothelial cells form simple squamous epithelium and normally constitute a non-thrombogenic surface preventing blood clots from sticking to the sides of the blood vessels and obstructing blood flow. This function is a result of the heparan sulfate contained in the endothelium which activates antithrombin III, thereby reducing the effects of certain elements of the coagulation cascade. When endothelial cells become damaged the endothelial progenitor cells (as they are usually known) are responsible for carrying out reparative work to prevent further damage and obstruction of the blood vessels which could, potentially, lead to ischaemia and tissue damage.
Growing New Blood Vessels with Stem Cells
Vasculogenesis is the name given to the process of blood vessel formation by the endothelial cells, most of which has occurred during foetal development. However, some endothelial cells continue to circulate in the blood during adulthood and there are certain conditions which can increase or decrease their population and activity. Early research led to the belief that endothelial stem cells were simply embryonic angioblasts as they behaved as such. Research in the 1990s confirmed the existence of endothelial cells in adult tissue and scientists have now realized that these stem cells are active in the vascularization and angiogenesis connected with tumor growth. Markers of endothelial stem cells have observed their migration from the bone marrow through the circulation to the site of a tumor where they may then be incorporated into the growing network of blood vessels feeding the tumor’s growth. Destroying the endothelial progenitor cells in the bone marrow through myeloablation has been shown to decrease vascular development and inhibit tumour growth.
Endothelial Stem Cells and Cardiovascular Disease
Circulating endothelial stem cells at higher levels in patients with cardiovascular disease are, however, associated with a better prognosis making their role quite complex. After an initial adverse cardiovascular event such as myocardial infarction (heart attack), endothelial progenitor cells become mobilized to the region in order to restore the optimum function of the damaged blood vessels. Some medications, such as ACE-inhibitors, which are commonly used to treat cardiovascular disease have recently been connected to an increase in circulating endothelial progenitor cells which, most likely, explains a significant degree of their benefit. Research has, therefore, become focused on the systematic use of endothelial progenitor cells injected into the area of ischaemia in order to reverse the damage and heal the blood vessels obstructing circulation.
Read More –> Research on Endothelial Stem Cells
