What are Induced Pluripotent Stem Cells?

Induced pluripotent stem cells are cells that have been manipulated in the laboratory to become pluripotent. Pluripotent stem cells are stem cells that have the potential to develop into almost any other kind of body cell. The only naturally occurring pluripotent stem cells are embryonic stem cells (ES cells).

Researchers hope induced pluripotent stem cells (iPS cells) will provide a source of artificial pluripotent cells. These cells are produced by genetically coaxing an ordinary body cell, called a somatic cell, into becoming a stem cell. They have none of the ethical problems that ES cells have, but hypothetically should have the same potential to treat diseases and injuries.

The first iPS cells were developed in mice in 2006 by using a retrovirus to modify the DNA of somatic cells. Researchers were deeply concerned about this method because of the dangers of retroviruses. These concerns would have hampered research into therapies using iPS cells. The first iPS cells were not viable, but they helped researchers identify the key genes that cause a cell to become pluripotent.

Research continued, identifying new pluripotency genes and eliminating certain genes that can cause cancer, but still used retroviruses. In 2008, a breakthrough was achieved: researchers created iPS cells using adenoviruses instead of retroviruses (Stadfeld et al. 2008). Adenoviruses are common viruses that do not insert themselves into the host's genome. This achievement means that safe iPS cell treatments might be possible.

Induced pluripotent cells could hypothetically be used for the same purposes as embryonic stem cells. They have several advantages over embryonic stem cells. For example, they can be autologous — that is, derived from the host's own cells — and therefore would not cause an immune response. They can also be isolated from patients with genetic diseases to further research into those diseases.

Notably, iPS cells are free of the ethical constraints that overshadow ES cells (Condic and Rao 2008). They are obtained without the destruction of embryos nor with the creation of clones.

More research must be done into iPS cells to ensure that they are safe. To be useful, they must be shown not to cause cancer and not to cause genetic problems related to the use of retroviruses. One day, iPS cells may be the solution to the embryonic stem cell controversy.

• Maureen L. Condic and Mahendra Rao. "Regulatory Issues for Personalized Pluripotent Cells." Stem Cells 2008; 26:11(2753 -2758).
• M. Stadtfeld, M. Nagaya, J. Utikal, G. Weir, and K. Hochedlinger. "Induced pluripotent stem cells generated without viral integration." Science 2008 Nov 7; 322(5903):945-9.