Adult stem cells
Adult stem cells are hidden deep within organs, surrounded by millions of ordinary cells, and may help replenish some of the body’s cells when needed. In fact, some adult stem cells are currently being used in therapies. They have been found in several organs that need a constant supply of cells, such as the blood, skin and lining of the gut, and have also been found in suprising places like brain, which is not known to readily replenish its cells. Unlike embryonic stem cells, adult stem cells are already somewhat specialized. For example, blood stem cells normally only give rise to the many types of blood cells, and nerve stem cells can only make the various types of brain cells. Recent research however, suggest that some adult stem cells might be more flexible than previously thought, and may be made to produce a wider variety of cell types. For example, some experiments have suggested that blood stem cells isolated from adult mice may also be able to produce liver, muscle and skin cells, but these results are not yet proven and have not been demonstrated with human cells. Nevertheles, scientists are working on finding a way to stimulate adult stem cells, or even other types of adult cells, to be more versatile. If they succeed, it could provide another source of unspecialized stem cells.