Tissue engineering is the use of cells and other materials to repair, replace, or enhance natural body tissue. This can be used to treat a disease or correct a problem that occurs with an organ or tissue in the body.

 

HEART ATTACKS

A heart attack is caused by a lack of blood flow to the heart. Blood flow can be cut off by things like blood clots or fatty build-ups that block the flow of blood in a vessel. Because cells need the nutrients and oxygen found in the blood in order to survive, losing blood flow causes these cells to die, killing the heart tissue. Even after blood flow to the heart is restored, the dead tissue is not able to fully regrow. The death of such tissue makes the heart weaker. A weak heart is not as strong and cannot pump blood around the body as easily. This means other muscles and organs might not get the blood they need, causing other health problems.

 

​Healing that naturally occurs in the heart can also cause problems because the tissue that forms is stiffer and can’t pump blood as well as normal heart tissue. This tissue can also have problems transmitting the electrical signals that travel around the heart and tell different parts of the heart when to beat. If the heart can’t beat at the right rhythm, then blood isn’t pumped as smoothly around the body. Unlike some other organs and tissues in the body, the heart is not able to be easily replaced. Over your lifetime, only half of all of the heart cells you are born with get replaced, meaning a damaged heart tissue is not able to be replaced with healthy tissue easily. One way that scientists have tried to treat hearts that have been damaged by heart attacks is by using stem cells to regrow the tissue that has died. If this tissue were able to be regenerated, then the heart would be as strong as it was before and would be able to pump blood as well as if the heart attack had not happened at all.

 

Problem: Parts of the heart die after a heart attack

Solution: Use stem cells to regrow parts of the heart that have died

 

Treating the heart with stem cells

If we want to treat the heart with stem cells to regrow damaged tissue, we need to figure out what kind of stem cells we need to use to regrow part of the heart. The heart is mainly made of cells called cardiomyocytes, or cardiac muscle cells. Cardiomyocytes are similar to other muscle cells found in other parts of the body but have a few key differences. These differences mean that other muscle cells can’t be implanted into the heart to regrow the cells that have been lost (other muscle stem cells can be used to regrow the heart), as they can only differentiate into other muscle cell types. While there are stem cells in the heart, there are not very many of them, and they are hard to get to. This makes using adult cardiac stem cells less desirable. Because most of the heart cells a person is born with stays with them throughout life, we know that a viable option for regenerating heart muscle is using embryonic stem cells, since they become the cells you are first born with.

 

Real world science

In one experiment that scientists performed on monkeys who had heart attacks, they used embryonic stem cells. They then had to figure out how to get these stem cells into the heart so they could regrow the damaged heart tissue. They found that they could use a needle in a syringe and inject the stem cells and a “pro-survival cocktail” into and around the edges of damaged heart tissue. 14 days after the injection of stem cells, the scientists found that the damaged areas of the heart had become remuscularized. This means the stem cells grew into cardiomyocytes and repaired some of the damage from the heart attack. After 84 days, the cardiomyocytes were the same size as cardiomyocytes from normal heart tissue, indicating the cardiomyocytes from the stem cells were becoming like the cells in the original cells that were in the heart before. Blood vessels had also grown into the new heart tissue, supplying it with blood. Additionally, the new tissue was electrically linked to the undamaged tissue and was able to beat together at the same rate. These all indicate that the use of embryonic stem cells to regrow damaged heart tissue is possible and works fairly well.

 

Issues with trying to regrow damaged heart tissue

This treatment was not without any problems, though. Early after the injection of stem cells, within the first two weeks the heart was more likely to experience arrhythmias. Arrhythmias are when the heart does not beat with the rhythm that is needed to pump blood effectively to the body. This problem indicates that early on, the new cardiomyocytes were not fully integrated into the heart and were not completely linked electrically.