More cloning, but still no stem cells
Posted by Jesse Reynolds February 12, 2009
Biopolitical Times
In the last two months, three teams of researchers have created human clonal embryos. Before them, only the researchers at the biotech company Stemagen had reported creating a human embryo via somatic cell nuclear transfer that appeared to be viable enough to potentially yield stem cells. However, none of the groups reported taking that step, and thus the current round of reports means little for that highly-touted endeavor.
Of course, somatic cell nuclear transfer requires human eggs. The Stemagen paper described how these were obtained, a process that we felt skirted California law. In contrast, none of the three recent papers mention where or how they got eggs, or how the women who provided them were treated. Were the women paid? Were they undergoing egg extraction for reproductive purposes, or just for research? How old were they? How were they recruited?
Two of the new papers (1, 2), both from Chinese teams, simply describe their successful method of creating the clonal embryos. The paper by the group led by Robert Lanza of the struggling biotech Advanced Cell Technology goes a step further. It compares the epigenomics of clonal embryos that were created using human eggs with those created using animal eggs, the latter of which has been proposed as an alternative to the former. This work indicated that the clonal embryos created using animal eggs (i.e., "cytoplasmic hybrid embryos") may not yield useful stem cells, as their epigenetic characteristics are significantly different from those created with human eggs.
Some may conclude that women's eggs are therefore necessary for cloning-based stem cell research. Other stem cell scientists are moving away from cloning techniques altogether. Alan Trounson, president of the California stem cell research agency, seems pessimistic about its prospects:
Of course, somatic cell nuclear transfer requires human eggs. The Stemagen paper described how these were obtained, a process that we felt skirted California law. In contrast, none of the three recent papers mention where or how they got eggs, or how the women who provided them were treated. Were the women paid? Were they undergoing egg extraction for reproductive purposes, or just for research? How old were they? How were they recruited?
Two of the new papers (1, 2), both from Chinese teams, simply describe their successful method of creating the clonal embryos. The paper by the group led by Robert Lanza of the struggling biotech Advanced Cell Technology goes a step further. It compares the epigenomics of clonal embryos that were created using human eggs with those created using animal eggs, the latter of which has been proposed as an alternative to the former. This work indicated that the clonal embryos created using animal eggs (i.e., "cytoplasmic hybrid embryos") may not yield useful stem cells, as their epigenetic characteristics are significantly different from those created with human eggs.
Some may conclude that women's eggs are therefore necessary for cloning-based stem cell research. Other stem cell scientists are moving away from cloning techniques altogether. Alan Trounson, president of the California stem cell research agency, seems pessimistic about its prospects:
Working with human embryos is also impractical because the high failure rate means it takes hundreds of eggs to create a single stem cell line, said Alan Trounson, president of the California Institute for Regenerative Medicine.
"Most people are working on IPS cells (stem cells derived from skin) rather than nuclear transfer because it's so difficult to get human eggs," Trounson said.
"Their work is endorsing that we could use human eggs but I don't think it helps us, to be honest, in actually being able to do it because it doesn't show that it could be improved dramatically."
Trounson said human cloning can still be important in addressing some serious genetic diseases because it would allow for the manipulation of mitochondria, which run cell function and contain DNA.
Previously on Biopolitical Times: