In 1963, while experimenting on a dead mouse, a pair of scientists observed a unique blend of specialized blood cells, also known as stem cells. In recent years, stem cell therapy has revolutionized medical technology and has extended countless lives. Stem cells are referred to as “undifferentiated” cells because they have not fully committed to a developmental path that will form a specific tissue or organ. The process of changing into a specific cell type is known as differentiation. When a stem cell divides, it has the choice to remain a stem cell or become another cell with a more specified function, such as a muscle cell or a brain cell. Stem cells are unique compared to normal body cells because they can renew themselves through cell division, even after long periods of inactivity. In addition, under certain conditions, they can be induced to become tissue or organ-specific cells with special functions.
For example, if the person has heart disease, the cells could be injected into the heart muscle. The healthy transplanted heart muscle cells could then contribute to repairing defective heart muscles. Doctors have performed stem cell transplants, also known as bone marrow transplants. In stem cell transplants, stem cells replace cells damaged by chemotherapy or disease or serve as a way for the donor’s immune system to fight some types of cancer and blood-related diseases. Recently, scientists primarily worked with two kinds of stem cells: embryonic stems cells or “adult” stem cells. In 2006, researchers made a breakthrough by identifying adult stem cells to be “reprogrammed” genetically to assume a stem-like state. This new type of stem cells was subsequently called induced pluripotent stem cells, or iPSCS. Even though adult stem cells are easier to attain, embryonic stem cell research is considered to have the greatest potential for delivering medical and scientific breakthroughs.
Embryonic stem cells, as their name suggests, are derived from embryos and are obtained from the inner cell mass of the blastocyst, a hollow ball of cells that forms three to five days after an egg cell is fertilized. Embryonic stem cells come from embryos that are three to five days old. At this stage, an embryo is called a blastocyst that has about 150 cells. They are pluripotent stem cells, meaning they can divide into more stem cells or become any type of cell in the body. This versatility allows embryonic stem cells to be used to regenerate or repair diseased tissues and organs. Human embryonic stem cells have been derived primarily from blastocysts created by in-vitro fertilization for assisted reproduction that were no longer needed.