Researchers have successfully reprogrammed adult cells in a living animal for the first time, creating stem cells that have the ability to grow into any tissue found in the body.
Until now these stem cells, known as induced pluripotent stem cells, have only ever been created in Petri dishes in the laboratory after being removed from the animal.
However, researchers at the Spanish National Cancer Research Centre in Madrid, Spain, were able to create these cells in the bodies of living mice.
They found that they could reprogram adult cells from the kidney, stomach, intestine and pancreas using a cocktail of “reprogramming factors”.
It raises the hope that damaged organs could be repaired in patients by reprogramming some of their own adult cells and then encouraging them to generate new tissue.
However, Dr Manuel Serrano, who led the research which is published in the journal Nature, said it would be at least five years before the first clinical trials to reprogram adult cells in human patients.
He said: “The main surprise of our work is that it is possible to generate pluripotent stem cells directly in the tissue in living organisms.
“We can imagine that transitory reprogramming could help in the natural regeneration of damaged tissue.
“In principal we hope that it could help to repair any kind of damage like in the heart, brain or liver, but we have still to find which will respond best.”
The research, which is published in the journal Nature, used genetically modified mice that carried a gene cassette that caused them to produce the reprogramming factors.
They were given a drug in their drinking water that turned the genes on and caused the reprogramming factors to be released, leading to the development of induced pluripotent stem cells that were similar to the stem cells found in the early stages of a developing embryo.
These have the capacity to develop into almost any other tissue found in the body, although the scientists have still to show that this can occur inside the mice.
In patients, such reprogramming could be targeted by injecting the factors at a local site.
However, creating inducted pluripotent stem cells in the body also carries risks as they also have the ability to develop into cancer cells.
Dr Serrano said they would have to do more research to establish how they could control the development of the reprogrammed cells so they did not produce tumours.
Prof. Chris Mason, an expert in regenerative medicine at University College London, added that the reprogrammed cells would also need to be guided to ensure they developed into the right sort of tissue within the body.
He said: The cells that will be useful will not be the pluripotent stem cells, but their more specialised 'adult' offspring.
“This is an interesting proof of concept of the first step in the process, but it still needs these induced pluripotent stem cells to be safely converted to useful 'adult' cell types in the body.
“The major challenge will be tightly controlling every step in this potential approach to treating patients in order to deliver clinical benefits whilst avoiding significant complications."