Adult Stem Cells

Stem cells are in your body for your entire life, replacing worn out cells and helping with illness and injury. Adult stem cells are of different types, depending on the organ they are found in – so adults have bone stem cells, brain stem cells, muscle stem cells and so on. Often they lie quietly in your organs for years at a time (much longer than most cells, which are replaced regularly), and become active only when you’re injured, or sick, or need a supply of new cells. When you’re injured, for example, stem cells ‘wake up’, replace damaged and lost cells, and then ‘go back to sleep’.

Usually, each kind of adult stem cell can produce only cells that belong to the organ in which the stem cell itself is found. So brain stem cells can produce various types of brain cell, but not bone cells or muscles.

But scientists are finding exceptions to this rule, which is exciting because it could mean that in the future stem cells from one organ could be used to repair or replace some other part of the body. When a stem cell from one organ generates cells from another organ, it is said to demonstrate "plasticity".