Stem cells made without embryos?
cells that could avoid the use of human embryos, potentially
bypassing one of the major obstacles to the development of
therapies based on this technology.
Researchers Kevin Eggan, Douglas Melton, and colleagues of Harvard University's stem Cell Institute will report in the 26 August edition of the journal Science that it may be possible by fusing two cells together to some day produce cells with the properties of embryonic stem.
The researchers caution, however, that many daunting challenges must still be overcome and the promise of their work should not be seen as a reason to slow present research efforts.
Current stem cell research has generated controversy because it involves the destruction of human embryos, or it requires women to donate unfertilised eggs.
In therapeutic cloning, a nucleus from an adult cell (for instance, a skin cell) is injected into unfertilised egg whose own genetic material has been removed. The egg reprograms the skin cell nucleus to an embryonic state, allowing it to initiate the development of an early embryo without the need for fertilization.
Researchers in Korea recently showed that the resulting embryos can be used to make embryonic stem cells that are genetically identical to the skin cell donor. But that method is technically difficult, involves the use of embryos, and because it requires donated human eggs, it is unlikely that it could ever be scaled up for widespread clinical use.
Moreover, the creation and destruction of embryos is controversial in the US, although this type of research is carried out in Europe and elsewhere in the world. In 2001 US President George W Bush ruled that federal money could only be used for research on embryos that already existed at that time, meaning that only a limited amount of stem cell stocks have been available to US researchers.
The HSCI researchers have taken a quite different approach, fusing an entire skin cell to an existing embryonic stem cell. The result is a hybrid cell with two sets of genetic material, one from each parent.
Using sophisticated 'DNA chip' technology, the Harvard team was able to show that cell fusion causes thousands of genes from the skin cell to be reprogrammed to an embryonic state.
Even more striking, they found that the fused hybrids retain many of the properties of embryonic stem cells, including the ability to differentiate into multiple adult cells types.
This is an important result because it suggests that adult cells could some day be converted into embryonic stem cells without using human eggs and without creating cloned human embryos. But if this kind of reprogramming is really possible, it is likely to take many years and many further studies, on embryos as well as hybrid cells, before this technique offers an alternative method of producing stem cells, say the researchers.
