Reprogramming adult cells
All specialised cells in the body were once stem cells. In recent years, scientists have been trying to find ways of 'reprogramming' these cells, to help them regain their pluripotency so that they can become any type of cell in the body. This technique would involve the genetic manipulation of a cell taken from the patient, and would not require the use of any kind of embryo.
In May 2006, Japanese researchers became the first to report the reprogramming of adult mouse skin cells, helping them regain the pluripotency seen in embryonic stem cells. The science seemed relatively simple: they added genes for four transcription factors - which express proteins involved in gene activity - to the growing cells and so-called induced pluripotent stem (iPS) cells were made.
Since then, several groups have published reports of reprogramming mature human skin cells to a pluripotent state.
These are exciting advances, particularly as the creation of iPS cells does not require the use of embryos - the limited supply of which is a key barrier to current stem cell research. However, a number of key questions about iPS cells remain. To date, research in this area has relied on viral vectors for getting the genes required for reprogramming into cells. Researchers are still to establish whether the integration of the viral genes into the cells' genome and/or some other genetic effects of the process plays some part in the reprogramming. It is also unclear which genes are required for the actual reprogramming, and which are required to trigger cell proliferation.
The major question though is whether iPS cells and embryonic stem cells are equivalent. To find out, researchers are comparing iPS cells and embryonic stem cells in a number of ways, including by looking at proteins on the surface of the cells that indicate pluripotency, and at the expression of genes within the cells.
Image: Neurons and astrocytes from neural stem cells; Steven Pollard, Wellcome Images
