Multicellular organisms begin as a single cell in the form of a zygote. The zygote develops into an embryo through mitosis. The cells in the embryo also start to differentiate, that is, the cells develop features that enable them to perform specific functions and become specialized cells.
Cells that have not yet differentiated are called stem cells. In other words, stem cells have the potential to differentiate into different types of cells. Stem cells can differentiate into cells with different functions such as muscle cells, blood cells, nerve cells, or cardiac cells.
There are two types of stem cells:
- Embryonic stem cells: Embryonic stem cells are cells from the embryo. They can differentiate into any type of cells in the human body.
- Adult stem cells: Some stem cells remain in adult bodies as adult stem cells. Adult stem cells can only differentiate into certain type of cells. For example, stem cells found in the blood marrow can only differentiate into different types of blood cells.
Benefits and Risks of Using Stem Cells in Medicine
- Stem cells can be used to replace damaged cells. Scientists can stimulate stem cells to differentiate into specific type of cells, such as heart muscle cells. The specialized cells can then be implanted into a patient suffering from diseases, such as heart disease. The implanted heart muscle cells can help to replace damaged heart muscle cells.
- It is even possible to grow a whole new organ from stem cells for transplant.
- If a patient's own stem cells are used for treatment, there is less risk of immune rejection.
- Stem cells can be used for drug testing. By generating the specific type of cells that a new drug is targeting, scientists can study the safety and effectiveness of drugs. For example, drugs for treating nerve diseases can be used on nerve cells generated from stem cells. Scientists can then look at whether the drug had any effect on the cells and whether any cells were damaged from the drug.
- There are ethical issues regarding the use of embryonic stem cells. Since obtaining embryonic stem cells destroys embryos, using embryonic stem cells has led to controversies regarding right to life. Questions on when human life starts and whether embryos should be regarded as a 'person' is still ongoing.
- There is no guarantee of the success of stem cell therapy because the stem cell therapy is still at its development stage. Mutations can cause stem cells to develop into cancer cells. It is also unclear whether there will be any long-term side effects.
- It is difficult to find stem cell donors.
- It is difficult to store and process stem cells.