There are currently three main groups of stem cells that are being investigated for their potential use in research and medicine. They differ in their degree of differentiation and ability to self-renew. In the human:
- Adult stem cells are more specialised than embryonic stem cells. They are found in the majority of tissues and organs in our body and generate the mature cell types within that tissue or organ. They have a restricted ability to produce different cell types and to self-renew.
- Embryonic stem cells come from a four to seven-day-old embryo. They have the ability to form virtually any type of cell found in the human body, but are not capable of developing into a whole new organism.
- Induced Pluripotent stem cells are created when a mature adult cell, such as a skin cell, is reprogrammed to become a pluripotent stem cell similar to an embryonic stem cell. The methods for reprogramming are varied and changing rapidly
Stem cells that have the potential to develop into any of the cell types found in an adult organism are called pluripotent. Embryonic stem cells and embryonic germ cells are pluripotent.
Stems cells that only have the potential to make a few cell types in the body are called multipotent. Adult stem cells are multipotent.
Cells that are capable of forming a completely new embryo that can develop into a new organism are called totipotent. A fertilised egg cell is totipotent as it has the potential to develop into a new organism.
More information on the various types of stem cells can be found in this section of the website.