Three independent research groups have reported successfully causing skin cells from adult mice to revert back to an embryonic stem cell-like state; a technique that could potentially help to resolve the ongoing ethical debate over stem cell research. Published in the journal Nature, this groundbreaking research could lead to future treatments in humans for regenerating damaged tissue in diseases like Parkinson's or type 1 diabetes, or even for whole organ regeneration.
Shina Yamanaka, who led the Japanese arm of the study at Kyoto University, reported similar findings last year, but with some major flaws - while the 'stem cells' could be triggered to develop into any type of body tissue (called pluripotence), they had some behaviours which were not consistent with them being stem cells; for example the fact that live animals could not be generated from them.
This year Yamanaka's team returns, backed by the success of two other US research groups, with strong evidence that the three teams have now successfully produced 'induced pluripotent stem cells' (otherwise known as iPS cells). These cells have been used to produce viable embryos that survive to adulthood and that themselves produce offspring carrying the same iPS cells; a strong indicator that they are bona fide stem cells.
Through a surprisingly straightforward technique, say researchers, the iPS cells are produced by using a harmless virus to insert four basic genes into the genome of skin cell. Here they trigger changes that reprogramme the cell to revert back to an embryonic stem cell-like state.
If reproducible in humans, it is hoped that iPS cells could provide an unlimited and ethically favourable source of stem cells for research.
Speaking to The New York Times, the US Bishop, Richard Doerflinger, said the technique 'raises no serious moral problem, because it creates embryonic-like stem cells without creating, harming or destroying human lives at any stage'.
Although this finding represents a major breakthrough in understanding, there are some key issues which will need to be resolved before use in humans. Firstly, because the virus inserts the genes into the mouse genome at random, it could potentially activate cancer-causing genes. Secondly, one of the four genes needed to trigger the switch into stem cells is itself a cancer-causing gene, explaining why 1 in 5 of Yamanaka's mice went on to develop cancer.
Nonetheless, optimism levels are high and Yamanaka, quoted in Nature, says that his team are working 'day and night' to resolve these problems and that he expects 'some big success with humans next year'.