Embryonic stem cells can grow into any type of tissue in the body, and scientists hope they could one day be used to replace diseased organs with healthy, lab-grown replacements. But their use in medicine is controversial because it involves the destruction of human embryos, albeit at a very early stage.
The alternative method is taking normal cells from adults and reversing them to an unspecialised state, known as induced pluripotent stem cells (iPS), making them almost indistinguishable from embryonic stem cells. However this could prove to be less effective especially in elderly patients, who have the most to gain from the potential treatments, because their cells have deteriorated further.
By adding two new ingredients, known as transcription factors, to the method of generating adult stem cells, scientists were able to overcome this hurdle and "reset" many of the key markers of ageing in cells. These two new transcription factors are NANOG and LIN28.
Transcription factors are proteins that bind to DNA to control the transcription of a unique set of genes.