Stem cells are undifferentiated cells that can specialise to become a specific type of cell, such as a muscle cell. They can be found in some adult tissues (such as bone marrow) as well as embryos.
Not all stem cells can become any type of specialised cell. Their ability to differentiate into specialised cells is called potency and there are three main types; totipotent stem cells, pluripotent stem cells and multipotent stem cells.
Totipotent Stem Cells
A totipotent stem cell can divide into all cell types. This means it can differentiate into any type of specialised cell as well as extra-embryonic cells.
Extra-embryonic cells are cells that form the placenta and umbilical cord for an embryo.
An example of a totipotent cell is a fertilised egg cell. As well as being able to make the extra-embryonic cells and pluripotent cells they can also form more totipotent cells.
Pluripotent Stem Cells
Pluripotent stem cells can divide into any type of specialised cell, apart from extra embryonic cells and totipotent stem cells.
This means the can form all the cells of an embryo.
Multipotent Stem Cells
A multipotent stem cell can only differentiate into a limited number of specialised cells.
They have the ability to develop into several different cell types found in a particular tissue or organ.
For example, blood stem cells can differentiate into different types of blood cells. It is not fully understood, however, whether they’d be able to differentiate into other types of cells outside of their cell type.
Most adult stem cells are multipotent stem cells.
Uses
Stem cells are already used in medicine in the treatment of certain diseases. For example, bone marrow transplants are often given to leukaemia patients to replace stem cells killed by the cancer.
Whilst current uses are limited, research aims to find many more ways in which they can be used to treat a range of conditions. The body only has a limited capability of healing damaged tissues and organs. Due to their ability to specialise, stem cells could be used to replace damaged cells.
For example, people with spinal cord injuries may experience damage to their nerve tissues and stem cells could be used to repair the damaged tissue. Or, as another example, they could be used to grow organs for people who require a transplant. The waiting lists for some transplants are too long for many patients to receive one in time and so the ability to grow organs could save many lives.
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