Monday, August 22, 2005
All the papers and news services are reporting this morning on an article due out later this week in the journal Science but posted to their website Sunday (see AP/Yahoo, Boston Globe, Washington Post). According the news reports, the article describes the results achieved by researchers at the Harvard Stem Cell Institute when they fused adult skin cells with embryonic stem cells: the fused skin cells were "reprogrammed to their embryonic state." The Institute's announcement reads:
A new study by Kevin Eggan, Douglas Melton, and colleagues offers hope that it might be possible in the future to produce embryonic stem cells without using human embryos. The Harvard Stem Cell Institute researchers will report in the Aug. 26 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 unfertilized eggs. In therapeutic cloning, a nucleus from an adult cell (for instance, a skin cell) is injected into unfertilized 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. As researchers in Korea have recently shown, 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.
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.
The significant policy issue here is that, if the scientists can actually produce a totipotent embryonic stem cell, a plentiful source of new stem cells will have been created without the destruction of any embryos, a major limitation on federal funding rules announced by President Bush in August 2001. And once the DNA of the fused stem cell can be stripped away, the resulting embryonic stem cell will be a genetic copy of the skin-cell donor without first creating a clone of the donor, bypassing yet another ethical obstacle to workable stem-cell therapies. [tm]