Types of Stem CellsStem cells can be categorized into five types based on their ability to differentiate or their potency. The stem cell types are as follows:
- Totipotent Stem Cells
These stem cells have the ability to differentiate into any type of cell in the body. Totipotent stem cells develop during sexual reproduction when male and female gametes fuse during fertilization to form a zygote. The zygote is totipotent because its cells can become any type of cell and they have limitless replicative abilities. As the zygote continues to divide and mature, its cells develop into more specialized cells called pluripotent stem cells.
- Pluripotent Stem Cells
These stem cells have the ability to differentiate into several different types of cells. Specialization in pluripotent stem cells is minimal and therefore they can develop into almost any type of cell. Embryonic stem cells and fetal stem cells are two types of pluripotent cells.
- Induced pluripotent stem cells (iPS cells) are genetically altered adult stem cells that are induced or prompted in a laboratory to take on the characteristics of embryonic stem cells. Although iPS cells behave like and express some of the same genes that are expressed normally in embryonic stem cells, they are not exact duplicates of embryonic stem cells.
- Multipotent Stem Cells
These stem cells have the ability to differentiate into a limited number of specialized cell types. Multipotent stem cells typically develop into any cell of a particular group or type. For example, bone marrow stem cells can produce any type of blood cell. However, bone marrow cells don't produce heart cells. Adult stem cells and umbilical cord stem cells are examples of multipotent cells.
- Mesenchymal stem cells are multipotent cells of bone marrow that have the ability to differentiate into several types of specialized cells related to, but not including blood cells. These stem cells give rise to cells that form specialized connective tissues, as well as cells that support the formation of blood.
- Oligopotent Stem Cells
These stem cells have the ability to differentiate into just a few types of cells. A lymphoid stem cell is an example of a oligopotent stem cell. This type of stem cell can not develop into any type of blood cell as bone marrow stem cells can. They only give rise to blood cells of the lymphatic system, such as T cells.
- Unipotent Stem Cells
These stem cells have unlimited reproductive capabilities, but can only differentiate into a single type of cell or tissue. Unipotent stem cells are derived from multipotent stem cells and formed in adult tissue. Skin cells are one of the most prolific examples of unipotent stem cells. These cells must readily undergo cell division to replace damaged cells.
Stem Cell Information : National Institutes of Health
Image: Nissim Benvenisty / Russo E (2005) Follow the Money—The Politics of Embryonic Stem Cell Research. PLoS Biol 3(7): e234. doi:10.1371/journal.pbio.0030234