Stem Cells

Stem cells are the cells that reside in an embryo. They can generate any type of body cell and make any type of tissue, so they are sort of like the fountain of youth... There are two kind of stem cell. The first kind is called adult stem cells and they replenish different types of cells within a tissue. For example, blood stem cells regenerates 12 types of blood cells, and skin stem cells regenerate skin and hair. The second one is the kind one finds in an embryo, called pluripotent stem cell. Pluripotent stem cells can be planted in different environments and generate different cells. For instance, if a patient's heart tissue is damaged by a heart attack, one can plant pluripotent stem cells in his heart and the stem cells will generate heart cells to mend the damaged heart tissue. However, mammal cells cannot dedifferentiate, which means the pluripotent stem cell that can make all kinds of cells cannot be naturally generated from body cells. Nevertheless, there are three ways to make this happen:
1. Cloning
Scientists can inject the body cell genetic material into an egg, which had its DNA taken out. The egg will then develop into an embryo from which pluripotent stem cells can be extracted. Whereas, this method can not be used on human cells because it causes legal issues, and for some reason, it hasn't succeeded yet.
2. One can turn on the genes, which are normally active in only embryonic cells, in adult cells. In order to achieve this, one can use retrovirus as a vehicle to ship reprogrammed genes into adult cells and produce iPSCs (induced pluripotent stem cells). However, a lot of iPSCs are not properly made because  the genes are not properly turned on. As a result, these inadequate iPSCs cannot pass the pluripotency test. (1. Expose iPSCs to different environment and check if they can generate different types of cells. 2. Inject iPSCs into a mouse's skin and check if a tumor can be formed. 3. Inject iPSCs into an embryo and check if the iPSCs help embryonic development.) A disadvantage of this method is that the retrovirus and the reprogrammed genes can be inserted in the wrong place and produce cancerous cells.
3. Expose body cells to chemicals and turn on the genes that are active in pluripotent cells.

Stem cells has a lot to do with my research in treatments for Leukemia. The major treatment of Leukemia is stem cell transplantation. one extract the patient's blood stem cell before the patient receives chemo or radiation therapy and plants the blood stem cells back into the patient's body. The blood stem cell will make healthy white blood cells that kill the cancerous blood cells.