Angiogenesis

The human body is a complex structure. There are several organs are present in this body. There is a complex network of blood vessels that connects every organ in the body. The human body has a specific immune system that helps to affect the body from foreign elements or substances. Scientists often wonder by seeing the human body instruments. There is always a backup plan for the processes that are going on inside the body. Due to any reason, if one path gets blocked, then there is a way to resolve that situation. Also, the human body is well equipped with the prevention from outside damage. One of the processes that heal external damage is known as Angiogenesis.

Angiogenesis

Angiogenesis is the process that is integrated with the healing of the blood vessels or the capillaries. The main definition is to produce more capillaries or blood vessels from the existing ones. The capillaries that are already present in the body will help to develop more new blood vessels in a certain area. If there is damage to the blood vessels, then this angiogenesis process happens. Angiogenesis helps to develop blood vessels in the damaged area. There it helps to repair the damaged blood vessels.

Capillaries are very tiny blood vessels. They are not large as the vein or arteries. So, they do have not enough power to draw more blood to a certain region. If for any reason, in a certain area, there is a need to have more oxygen or blood. In those cases, there will be an angiogenesis process triggered. The existing blood capillaries that are placed nearby will help in this case. From those capillaries, new more capillaries will be formed. And they will help to supply more blood to that area.

Mechanism of Angiogenesis

The angiogenesis process is the process that can be observed in the body of the human being. This is the process that is occurred every time in our body. After the capillary development in the body, cell growth continues in the body. As a result, some cells might get low oxygen. This is the trigger to develop a new capillary to proved more oxygen to the cell. So, the angiogenesis process can be found there. But for that purpose, there should be some background present. And here, the background will be a Hypoxic cell.

1. Formation Of Hypoxic Cell: The cells that are placed near the blood vessels get more oxygen. As the oxygen is being transferred to the cells using the diffusion process. So, the cell that is placed near the blood vessels will get more oxygen. And the cells that are placed far from the blood vessels will get low oxygen. If the oxygen receives rate downs sharply, then there will be a change. If the cells start growing more, then the cells which are placed far from the blood vessel will get very low oxygen. That will create a state of the cell. That is known as the Hypoxic Cell. This means, there is a high definition of oxygen.
2. Secretion Of Vascular Endothelial Growth Factor: This is a special type of chemical. This chemical starts secrete by the hypoxic cells. The cell that becomes hypoxic gets this type of ability. This chemical is known as the VEGF. This is the chemical that provides a signal to the blood vessels. It provides a signal that the cells are deficient. Due to the growth of the cells, this type of problem arises. And this chemical secretes only when there is a low oxygen level in the cell. This is like an emergency call. The VEGF factor triggers the angiogenesis factor.
3. Acceptance Of Vascular Endothelial Growth Factor: Now, the VEGF chemicals will be accepted by certain receptors. There is a special receptor is present in the endothelial cells of the blood vessels. This VEGF chemical connects to the receptors and binds there. This binding provides a signal to the blood vessels. The blood vessels get the location of the cells where the low oxygen crisis is present. This chemical helps to mark the cell layer where the problem is going on. This is the second step in the angiogenesis process. This chemical triggers the breaking of the blood vessels layer.
4. Dilution Of Basement Membrane: Now, after the VEGF factor is received in the receptors, it is time to make a new capillary from the existing capillary. The endothelial cells are now in the activated form. Sometimes, they have termed the Tip cells. Now, from these tip cells, a special type of enzyme will be secreted. This enzyme is known as Protease. This enzyme secretes from the endothelial cells & acts on the basement cell membrane. The basement cell layer is the outer cell layer. This cell layer will be diluted in the special region. This is the surrounding region where the VEGF chemical binds with the receptors. Surrounding that area outer layer will be dissolved.
5. Formation Of New Capillary: Now, as the outer layer is dissolved, the endothelial cells start working there. As the VEGF chemical binds with the receptors of the endothelial cells. So they have the proper location of the cell layer. The endothelial cells will start developing rapidly there. And they will move to the affected region of the cells. Going close to the cells, they will make a loop with each other. As a result, a blood capillary is now present near the cells. So, there will be no more deficiency of oxygen. Now, the cells can again make a growth there.

Types of Angiogenesis

As angiogenesis means to produce new capillaries from the existing blood vessels. For that purpose, a blood vessel needs to be cut into two pieces. There are two layers are present in the blood vessels. The outer one is the basement membrane. And the inner one is the endothelial cells layer. There are elongated endothelial cells are present. For creating new blood vessels from the existing ones, there is a need to break these membranes. This breaking process can be done in two ways. Each type of angiogenesis follows only one way. Based on the path that follows angiogenesis, can be divided into two parts.

1. Sprouting Angiogenesis: This angiogenesis process is the first discovered angiogenesis process. This angiogenesis process can be visualized in the human body also. In this case, a blood vessel is not divided into two parts. Instead, they start making Sprout. This means they rely on new growths. With growing more, the existing capillaries can able to come close to the affected region. There will be a function of the receptors. A chemical signal is necessary to break the walls of the blood vessels to make new ones. There are some special receptors are present in the endothelial cells. From the affected region, a special chemical comes out. That chemical bind to the receptor. As a result, the breaking process starts here. This simple process can be viewed all the time in the human body. Whenever the blood capillary is injured, this way is followed. But this process is not started in early life. This process can be visualized in adulthood. In early life, there is another angiogenesis process that happens. 
2. Intussusceptive Angiogenesis: This is another type of angiogenesis process. But this process is very limited. Whenever anybody is in its embryonic from this process can be viewed. When a human baby starts growing, this process can be recognized. In this process, the existing blood vessels are divided into two parts. For starting this process, there is no need to have any chemical receptors trigger. This is a spontaneous process. The inner endothelial cells of the blood vessels started to move in each other direction. After some time, two endothelial cells layer will meet with each other. There they make the zone of contact. At this zone of contact, later the tight junctions will be formed. Then there will be lumen space arriving at that zone of contact. Eventually, from that zone of contact, two capillaries will be separated from each other. In this way, without making more endothelial cells, a capillary is divided & developed into two new capillaries. But this process stops at adulthood of the human. From that onwards, there will be a Sprouting Angiogenesis process happen.

Stimulations in Angiogenesis

Stimulations are those elements or things that trigger a certain process. Sometimes stimulation arises from the body itself. Or sometimes, there are stimulations are present that are coming from the outside of the body. Some stimulation triggers the reflex action in the body. Similarly, some stimulation causes Angiogenesis. There are mainly two types of stimulations present in the Angiogenesis process. Depending upon the presence of the chemical element in the body, this separation can be done.

Mechanical Stimulation

This is one type of stimulation that occurs before the Angiogenesis process. In this process, there is a very limited number of responsibilities for the chemicals. Or it can be said that there is the least amount of duty of any chemical. However, scientists are not yet confident about this type of stimulation. This type of stimulation is a very rare case. This situation occurred very less amount of time. So, this stimulation is still under the experiment process. But still, scientists have some theories on it.

In the Mechanical Stimulation process, there is no involvement of any chemical substances. So, there is no need to attach any chemical to any receptor. So, there is no interaction between receptors & chemicals. Instead, due to the presence of some chemicals in the cells, the Angiogenesis process happens there. The presence of such chemicals at a high level triggers the Angiogenesis process. That is the reason it is called Mechanical stimulation. Though in this theory, there are many controversies present.

Scientists provide an example of muscle fatigue. During excessive exercise, there might be a natural Angiogenesis process can find out. During exercise, in the muscle cells, there will be some changes. Like, in the muscle cells, one chemical is stored due to the tension in the cells. This chemical is known as Nitric Oxide. The high amount of Nitric Oxide present in the muscle cells leads to Angiogenesis. Nitric Oxide causes vasodilation of the blood vessels. As a result, Angiogenesis is common in this case. But scientists have not confirmed this process. So, there is some controversy regarding Mechanical Stimulation.

Chemical Stimulation

Other than Mechanical Stimulation, another stimulation is Chemical Stimulation. Here, the chemicals are responsible for most of the process. Unlike Mechanical Stimulation, the quantity of the chemicals present in the cells will not arise during the Angiogenesis process. Here, the chemicals are stored inside the cells. When there is a need to do Angiogenesis, the chemical is secreted from the cells & attach to the receptor. So, there is a function of receptor-chemical is present.

Here, when there is a need to do Angiogenesis, a chemical is secreted from the cells. And those chemicals attach to the receptors. These receptors are present in the blood vessels. Attaching to the blood vessels will trigger the Angiogenesis process. So, attaching to the receptor is the starting point of the Angiogenesis here. That is the reason this stimulation process is known as Chemical Stimulation.

There are a lot of chemicals are present in this process. Here, the chemicals are known as the stimulator. There FGF, VEGF, ANG, Ephrin, and many more stimulators are present. Among them, the very important stimulator is the VEGF. This is known as the Vascular Endothelial Growth Factor. This chemical helps to start the process of Angiogenesis. That is the reason, this chemical is highly important. Other chemicals help to maintain the Angiogenesis process & some help to stop the process. As VEGF is responsible to start the process, that is why the cancer genes create a replica chemical of VEGF to grow continuously.

Importance of Angiogenesis

Angiogenesis is the process that helps to repair the blood vessels of the body. Its importance can’t able to derive in simple words. When every animal is in its embryo form, angiogenesis starts working there. It helps to develop the blood capillary network in the body. So, when a child is grown up & is in its adulthood, the capillary network development will be ended. Now, the angiogenesis will maintain the blood capillary network. Whenever there will be some damage to the capillary, it will repair it using this process. In absence of this process, the blood capillary network will not develop more. And then any hurting from the outside will damage the network forever time. Angiogenesis helps to regulate the blood & oxygen supply in the body.

Angiogenesis process leading to Cancer

The angiogenesis process helps to make the growth of cells. But every cell has some proper limit to growth. After having growth, they stop growing more. But the cancerous cells are not including that list. They will always make growth there. But for growing in an unstoppable manner, they should have a good oxygen supply. But, the angiogenesis process will not help in this case. As this only helps the cells, that have a proper manner of growth. In those cases, cancerous cells use a different approach. This approach fools the angiogenesis process.

The cells that are growing continuously don’t have a proper workflow. Most of the cell organelles are destroyed there. To grow more rapidly, they need to have a good supply of oxygen. So, they use a proxy of the angiogenesis process. These cells secrete a chemical that is known as the Pro-Angiogenesis Growth Factor. This chemical is mostly similar to the VEGF factor. This chemical binding to the VEGF receptors. And it is pressure to do angiogenesis for the cancerous cells. So, they get a good supply of oxygen.

As a result, the cancerous cells start growing more. Even in serious cases, cancerous cells use these capillaries to move around in the body. And whenever they will get a place they start growing in that area also. During Chemotherapy, doctors try to block the blood vessels that provide oxygen to the cancerous cells. As if the oxygen supply cuts down there, the cells will not able to grow more. Otherwise, these cells will start to grow continuously & the individual will be affected by cancer.

Chemical Inhibition of Angiogenesis

Angiogenesis is an important process in the human body. There is no doubt that this process needs to execute in the body forever. But there must be some limitations in every process. Whatever the process is, that might be a good one, but still, also, there is a need to stop that process at a certain time. Angiogenesis is not other than that. The angiogenesis process needs to stop at a certain point in time. When the creation of blood vessels is completed, then there is no need to run the process more. Chemical inhibitors are used. There are two types of inhibitors are present. One that arises from the body itself. This is known as the Endogenous. Some need to be provided from the outside. These are known as the Exogenous.

Endogenous are those substances that help to stop the Angiogenesis process in the body. These substances are secreted from the body to stop the natural Angiogenesis process. These are the process that occurs routinely in the human body. After the creation of the blood vessel to the certain cell layer, these substances help to stop them. There are certain chemicals are present in the body. Like there are Angiopoietin, Endostatin, Prolactin & many more chemicals are present that act upon the Angiogenesis process to stop them. Prolactin is the most important inhibitor. As this acts upon the VEGF factor that increases the Angiogenesis process.

But the Endogenous chemicals are not sufficient to stop the Angiogenesis process that occurs due to cancerous cells. Cancerous cells can skip the influences of endogenous inhibitors. That is the time when there is a need to provide inhibitors from the outside of the body. These are known as the Exogenous. Like tofu, green tea acts as the exogenous inhibitor that stops the Angiogenesis process. Other than that, there are certain chemicals present that are injected from drugs or medicine. During the treatment of cancer, these drugs are used. In severe cases, chemotherapy can be used as an inhibitor of Angiogenesis.

Application of Angiogenesis

1. Angiogenesis in Therapeutic Target: This is the practice to find out the abnormal creation of the Angiogenesis process in the body. While the abnormal Angiogenesis process, there will be an increased level of chemicals. The most important chemical will be at a high level in the surrounding area. This helps to find out the affected region of the body. Using the process of Angiogenesis, this counter process is derived. Though this still needs to get more updated. But this can be used to find Angiogenesis.
2. Angiogenesis in Cancer: Angiogenesis is the main reason for cancer. As the cancerous cells need more blood than the normal blood cells. So, Angiogenesis helps to identify cancer in any individual body. If there is a trace of Angiogenesis in the body that is an indication of some abnormal situation going on in the body. This helps to act fast for the recovery of the individual before it gets very late.
3. Angiogenesis in Tumor Blood Vessels: Angiogenesis leads to cancer. But the very first step is the formation of the tumor blood vessels. These are the blood vessels that provide more blood to the cancerous cells. Daily, a cancerous cell can able to take the same amount of blood as 50-100 cells needed. So, there is a need to have a good amount of blood supply to that cell. Occurring Angiogenesis to neighboring cells can be able to reduce the cell flow to the cancerous cells. In this way, the formation of tumor blood vessels can be stopped.
4. Angiogenesis in Exercise: During exercise time, there is an increase in the Angiogenesis level in the body. As the cells in the specific region need to have more oxygen to survive. During exercise, there is an oxygen deficiency in the body. And Angiogenesis helps to maintain the deficiency in the body.
5. Angiogenesis in Cardiac Diseases: Most of the time, Cardiac Diseases are occurred due to less blood pressure in the body. Or sometimes the required amount of blood is not going to the valves of the heart. Angiogenesis helps to survive that situation. It helps to create new blood vessels to counter the disease. It is still research to produce more blood vessels by using triggers from the outside to counter this type of disease.
6. Angiogenesis in The Eye: An increased Angiogenesis process in the eye may be fatal. Excess blood might come to the retina. That might cause permanent blindness in some individuals. So, abnormal Angiogenesis sometimes not causes cancer. But might cause some other issues.
7. Angiogenesis in Body Organ Transplantation: Angiogenesis is the process that helps to maintain the host body & the transplanted organ. This helps to create blood vessels for the transplant body organ. In this way, body organ transplantation is being done in hospitals. So, Angiogenesis helps in body organ transplantation.