The Process of Angiogenesis
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What is Angiogenesis?
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Angiogenesis is a process whereby new capillary blood vessels are formed. This is a normal process in the body. Angiogenesis is essential for the healing of wounds. It plays an important role in restoring damaged tissue and restoring normal blood flow after injury. It is also an important component in the growth of the fetus during pregnancy.
How Normal Angiogenesis Produce Blood Vessels
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The production of blood vessels through angiogenesis follows an orderly process. First, injured tissues die. These dead tissues produce angiogenic growth factors that are distributed throughout the nearby tissues. These angiogenic growth factors bind to specific receptors of the existing blood vessels, prompting the endothelial cells to produce new molecules and enzymes, which dissolve tiny holes in the membranes of the existing blood vessels. The endothelial cells then flow through these dissolved holes towards the dead tissues, bringing along with them integrins that pull the newly formed blood vessels forward.
In order for the tip of the blood vessels to fit into the holes, matrix metalloproteinases are produced to dissolve the tissues on it. As the vessel expands, the tissue is fitted back around the vessel. Newly formed endothelial cells then form into blood vessel tubes, each connecting to each other to form loops for blood to circulate. Smooth muscle cells provide support to stabilize these newly formed blood vessels. When all this is done, blood can then begin to flow through these blood vessels.
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Angiogenesis and Diseases
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The body may sometimes fail to control the actions of angiogenesis. In some instances, angiogenesis may either lead to excessive growth of cells or capillary blood vessels, or it may not be able to produce enough blood vessels to sustain the cells of the body. When this happens, bodily disorders and health problems can occur. Excessive angiogenesis may lead to diseases such as cancer, rheumatoid arthritis, diabetic blindness, psoriasis, age-related macular degeneration and several other diseases. On the other hand, lack of angiogenesis can lead to chronic wounds, coronary artery disease and stroke.
Excessive Angiogenesis
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The human body contains at least 20 different angiogenic growth factors. When the body fails to regulate the production of these growth factors and more of them are produced than usual, the action of natural angiogenic inhibitors may be overwhelmed and more abnormalities may occur. The newly-formed blood vessels may destroy the normal tissues, feed on the dead tissues and then produce more angiogenic growth factors or blood vessels. The newly formed blood vessels may then multiply, some of which may lodge in other organs of the body. When this happens, cancer and other deadly diseases may occur.
Insufficient Angiogenesis
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Insufficient angiogenesis, a phenomenon opposite to excessive angiogenesis, may also occur. This is an instance when the body's tissues cannot produce enough angiogenic growth factors to support the production and growth of new blood vessels. When this happens, blood circulation may not be completed and tissue death may occur. Damaged tissues may not be completely healed or restored due to lack of blood vessels and as such, wounds may not heal. This condition can lead to abnormalities or diseases in the coronary artery and other organs of the body.
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