Not all stem cells are created equal. The potential for stem cells to differentiate into other specialized cells changes as an embryo develops. Stem cells can be:
Totipotent. In the early stages after fertilization — immediately after a sperm and egg join together and begin dividing — stem cells are considered totipotent. This means that these cells can form any type of cell, including those cells necessary for an embryo to develop into a human, such as placenta cells.
- Pluripotent. Several days after conception, as an embryo begins to develop, its stem cells become pluripotent. Such cells can form any kind of cell found in adults, making them very versatile. Unlike totipotent stem cells, however, they can’t become cells necessary for an embryo to develop into a human. Cells with similar properties are also found in fetal tissue. # Multipotent. Eventually, pluripotent stem cells become multipotent stem cells — the type found in adults. Multipotent stem cells can no longer develop into all or most cell types. Instead, they can develop into certain cell types within a specific tissue, organ or system. For example, bone marrow stem cells can develop into all types of blood cells, which are normally produced by your bone marrow, as well as bone, cartilage and fat cells. Stem cells in your brain can turn into nerve cells and other types of brain cells.
- Multipotent stem cells exist in certain tissues and organs throughout your body, including your brain, blood vessels, liver, muscles and bone marrow. Researchers believe that multipotent cells remain — undivided — in these parts until they’re called into duty to create necessary new cells, such as after a disease or injury.
Some scientists suspect that stem cells in one body part may be able to form cells used in other body parts, a quality called Plasticity. For example, a stem cell in your bone marrow that makes blood cells might also be able to make heart-muscle cells or liver cells.