types of stem cells

There are three main types of stem cells 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:

1. Embryonic stem cells come from a five to six-day-old embryo. They have the ability to form virtually any type of cell found in the human body.
2. Embryonic germ cells are derived from the part of a human embryo or foetus that will ultimately produce eggs or sperm (gametes).
3. Adult stem cells are undifferentiated cells found among specialised or differentiated cells in a tissue or organ after birth. Based on current research they appear to have a more restricted ability to produce different cell types and to self-renew.

Stem cells in culture

Stem cells growing in culture

In addition, umbilical cord blood stem cells are currently being used to treat a range of blood disorders and immune system conditions.

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 are pluripotent.

Stems cells that only have the potential to make a few cell types in the body are called multipotent. Adult stem cells appear to be multipotent.

Cells that are capable of forming a completely new embryo that can develop into a new organism are called totipotent. A fertilised egg is totipotent. None of the stem cells used in research appear to have this capacity.

More basic research is required to find out how stem cells can be located and extracted, kept alive in the laboratory, multiplied for extended periods of time, and directed to form specific types of specialised cells.