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For the third time in less than a year, human embryonic stem cells (hESCs) have been derived by cloning (that is, somatic cell nuclear transfer or SCNT) and reported in a major peer-reviewed journal. As a result, there is a renewed campaign for so-called “therapeutic cloning,” in which stem cells for medical treatments would be tailored to match a particular patient’s genome. And there is definitely a new push to extract and exploit women’s eggs.
The first published report, in Cell (online last May), was by Shoukhrat Mitalipov and his Oregon Health and Science University team. Their work was confirmed earlier this month in Cell Stem Cell by a consortium mostly from the Korean CHA conglomerate, with Robert Lanza of Advanced Cell Technology and other American contributors. A second confirmation by another research group, headed by Dieter Egli and colleagues at the New York Stem Cell Foundation, was published on April 28th as a Letter to Nature.
In all cases, the success rate was very low, and surprisingly variable. In the latest paper:
Although nuclear transfer blastocysts could be obtained with an efficiency of approximately 10%, developmental efficiency varied between different oocyte donors, even when other aspects of the nuclear transfer protocol were kept constant.
Overall, the latest experiments used 512 eggs from 35 women and developed four cell lines.
Nevertheless, these papers clearly represent a technical step forward for SCNT in humans. Other researchers are likely to adopt the new techniques, putting cloned human embryos into labs around the country. This underlines the urgent need to establish, at a federal level, legal prohibitions against human reproductive cloning. Though none of the scientists involved in these SCNT investigations supports such abuse of their work, there is clear reason for concern: A number of fertility doctors and others have made headlines with claims to be engaged in efforts to produce cloned human beings, the latest involving John Lennon’s tooth.
We also need much firmer federal regulation of the use of women’s eggs for research. Egli actually moved his work from Massachusetts to New York to take advantage of looser rules. The CHA organization has been vague about where and how the eggs they used were obtained; they may even have broken California’s law, which forbids paying for eggs (beyond reimbursement for expenses).
The sheer volume of women’s eggs required for SCNT is one of the reasons that personally tailored stem cells lines are unlikely to become a staple of medicine. (The women in the latest experiment were apparently paid about $8000 each — which comes to over a quarter of a million dollars for the four lines — and that would of course only be start of the costs involved, even for a limited application.) But that is exactly the goal that Egli has in mind, according to the Associated Press:
The new work is a step toward providing genetically matched replacement cells for transplant, said Dieter Egli of the New York Stem Cell Foundation Research Institute in New York.
“When you think about wider application of this technology for patients with diabetes, cardiovascular disease, [and others], you are talking about hundreds of millions of people. When you start talking about numbers like that, it’s just not going to be practical to use these cells in that patient-specific way.”
Indeed. Lanza’s proposed solution is to develop banks of therapeutic cells, so "you try to match tissue types, like with organ transplant now.” This is quite puzzling: It is unclear why it would require SCNT at all, rather than relying on embryonic stem cell lines derived from embryos that would otherwise be destroyed after IVF treatments. In any case, Lanza does remain committed to developing SCNT. After all, he just co-authored a paper on the subject, whose summary says:
Our study therefore demonstrates the applicability of SCNT for adult human cells and supports further investigation of SCNT as a strategy for regenerative medicine.
Surely he is not trying to eat his cake and have it too?
Despite its many dangers and drawbacks, there may be a role for SCNT in research, even if induced pluripotent cells (iPSCs) turn out to be an easier and more reliable source of therapeutic cells. Doug Melton of the Harvard Stem Cell Institute, who called the latest paper an impressive technical achievement, believes that
the cells would be useful as a research tool rather than a source of transplants. They could help scientists uncover what triggers Type 1 diabetes, he said, which could in turn lead to better therapies.
If research cloning is to be pursued, the United States must join the dozens of countries that have already established strict prohibitions against human reproductive cloning. And we must put in place firm, national and international, standards about the provision of eggs by women.
Previously on Biopolitical Times: