Last week, the journal Science formally retracted two stem cell papers published by Woo Suk Hwang and colleagues at Seoul National University in the Republic of Korea. In the first paper, published in February 2004, Hwang and colleagues purported to have cloned human cells for the first time (see ARF related news story); in the second, published in May last year, the researchers claimed to have generated 11 stem cell lines from somatic nuclei donated by nine different individuals (see ARF related news story). That second paper, which listed Gerald Schatten from the University of Pittsburgh School of Medicine, Pennsylvania, as senior author, seemed to herald an era of personalized stem cells, but it was not to be. Late last year, questions about the veracity of the data (see ARF related news story) led to investigations by Seoul National University. On January 6, the investigation committee released its conclusion that both papers were fabricated.

Despite the retraction (see full text at the Science website), the fallout from this debacle continues. Editors of the journal Stem Cells are now carefully scrutinizing papers published by investigators who have worked previously with Hwang (see Stem Cells expression of concern), while Science is reporting that several other journals, including Molecular Reproduction and Development, are in the midst of their own investigations. One journal, Biology of Reproduction, has already retracted a paper because it used images that also appeared in Hwang’s 2004 science paper (see http://www.sciencemag.org/cgi/content/full/311/5759/321b).

The only good news from all of this seems to be Snuppy, the world’s first cloned dog. The investigation committee at Seoul National University reported that Snuppy is indeed a clone of Tie, the Afghan hound (see Lee et al., 2005).—Tom Fagan.

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  1. This should be extremely exciting news for the public. In theory, these ES cells isolated from cloned human embryos may not cause immune rejection after transplantation since they carry the nuclear genomic information from the host. It sounds as if we could eventually treat diabetes, osteoarthritis, Alzheimer's, Parkinson's, and other diseases using this technology. In theory, we might not even have to worry about aging because, thanks to this technology, we might be able to generate our own tissues or even organs.

    However, I wonder why the authors used both the egg and the cumulus cells from the same person in this study, if they could have gotten somatic nuclei from other donors. Because of this, the authors cannot rule out the possibility that the cloned embryo developed by means of parthenogenesis rather than nuclear transfer. I would want to see male nuclei transferred to the embryo instead.

    Another question would be whether the cloned ES cell is fully functional as a normal cell. Cloning by nuclear transfer is an inefficient process in which most clones die before birth and survivors often display growth abnormalities (Rideout et al., 2001). This may be due to the tissue-specific DNA methylation pattern from somatic nuclei used in cloning (Humpherys et al., 2001). Although Munsie et al. reported that pluripotent stem cells can be derived from reprogrammed nuclei of terminally differentiated adult somatic cells (Munsie et al., 2000), cloned ES cells may also be modified by tissue-specific epigenesis that has occurred in the somatic cells.

    Finally, I just want to point out that "therapeutic cloning" is "human cloning." I will not discuss the ethical issues, but the reader may want to consider that one of the authors, Dr. Jose B. Cibelli, was Vice President of Research at Advanced Cell Technology Inc. The study was done with more than 200 human eggs, which were donated from 16 women. These women underwent hormone treatment to stimulate their ovaries to overproduce maturing eggs.

    References:

    . Nuclear cloning and epigenetic reprogramming of the genome. Science. 2001 Aug 10;293(5532):1093-8. PubMed.

    . Epigenetic instability in ES cells and cloned mice. Science. 2001 Jul 6;293(5527):95-7. PubMed.

    . Isolation of pluripotent embryonic stem cells from reprogrammed adult mouse somatic cell nuclei. Curr Biol. 2000 Aug 24;10(16):989-92. PubMed.

    View all comments by Kiminobu Sugaya
  2. See 23 January 2006 Update to Rao's comment on stem cell research by this research group. Designer Cells
    The use of stem cells for therapy faces a number of hurdles including the issues of immune suppression. The body has a surveillance program to differentiate self from non-self that recognizes transplanted cells as foreign and rejects them. Clinicians and scientists have succeeded in transplanting organs or performing bone marrow transplants by matching donor tissue to the recipient and thus bypassing or suppressing the immune response. Such strategies have been successful as evidenced by the large number of organ and bone marrow transplants performed each year, although it often necessitates lifetime immunosuppressive therapy.

    A second hurdle that hinders the wider application of cell therapy is the lack of an abundant and reliable source of cells. Both adult stem cell (SC) and embryonic stem cell (ESC) proponents have argued that stem cells can solve this source issue by providing a reliable, potentially unlimited source of cells. Adult SC proponents have suggested that using stem cells from adults may be better, in part, because personalized stem cells could be utilized bypassing the immune issues altogether. ESC proponents had argued that if a sufficient number of lines were available, one could match, much as we do with blood transfusion, organ banks, or cord blood, or generate personalized ESC lines by SCNT using techniques that are currently available (though not applicable for federal funding in the US and banned in others).

    The group in Korea led by Woo Suk-Hwang showed that this is indeed possible. In an elegant series of experiments, they derived a series of personalized ESC lines that were pluripotent, karyotypically normal, and matched the DNA profile of the donor. Equally important, they derived these lines on human feeders that were derived from the same patients whose donor nuclei were used to develop these lines, limiting exposure to xenoproducts. Though no efficiency numbers were reported, these must be reasonably good for this group to have derived the number of cell lines they did and suggests that this could indeed become relatively routine.

    The blastocysts used in this experiment were not matched in any way to the donors, and it is reasonable to assume that mitochondria were not donor-derived, and as such, these cells contain genetic information from more than one individual. It will be important to determine if cells with mismatched mitochondria behave differently from other cells in transplant procedures, and this group is uniquely placed in testing this important biological question.

    While no doubt their results are of importance for the transplant field, I believe it is also an unprecedented advance for basic biologists. We will be able to study for the first time issues such as aging and its reversal. By allowing one to examine the process of epigenetic remodeling in a dish (over a short time period), one can begin to understand factors that regulate reactivation and suppression of genes in different tissues and organs, and by allowing homologous recombination in ESC that are patient-specific, one can begin to probe pathways that are disease-specific and evaluate methods to cure specific genetic defects. By allowing one to create patient-specific cell lines, one can imagine developing/identifying specific drugs that are ideal for treatment. It is heartening to see that this group identified such fundamental questions as an important reason why such research needs to progress.

    It is these fundamental issues that are of importance to the Alzheimer community (at least initially), and I fully expect that one could and will develop a battery of ESC lines from people who have an unambiguous diagnosis of Alzheimer's to begin to evaluate pathways and mechanisms that lead to this progressive disease.

    It is important to note that this research is not illegal in the United States (although efforts are underway to make it so). It is not, however, eligible for federal funding, and one cannot use the infrastructure of tools and techniques developed over the past 20 years in the United States with the aid of the NIH/DOD/NSF funding to study the newly developed lines. This inability to use the cutting-edge strategies on SNP mapping, whole genome analysis, methylation, and epigenetic analysis pioneered in the States will no doubt slow down efforts in this country. It is perhaps coincidental that these results appeared just as the Senate and Congress begin debating expanding the availability of cell lines. One can hope that the US Government will take into account all recent advances to determine what would be the best policy for the NIH to follow.

    View all comments by Mahendra Rao
  3. I had reviewed the potential of both this paper and this group's 2004 Science paper to affect how stem cell science was done. It reflected in my mind a possible solution to the issues of immune rejection and efficiency that had limited the potential use of these cells. The reported results suggested that both problems could be solved and, indeed, had been solved.

    It was with great disappointment that I learned that the published data that we relied on was almost totally fabricated. These papers have now been withdrawn, and while the potential of these solutions remains, clearly we are some way off from having reduced it to practice.

    I am saddened that the field had to suffer this agony of embarrassment, but am heartened by the courage of the young investigators who pushed for an investigation, and by the robustness of the investigative process that helped uncover the misdeeds.

    View all comments by Mahendra Rao
  4. Normal embryonic development requires fertilization with genomic contributions from both maternal and paternal genomes. During this process genetic rearrangements occur which alter the exact contribution made by each parent to each progeny, and this contributes to every individual’s unique genomic profile. However, the same events that confer genetic diversity also create difficulties for transplant biologists, who have to match donors and recipients to prevent immune rejection of “foreign tissue.” Multiple strategies to bypass the immune intolerance barrier have been developed, though the current strategy reported by Dr. Moon and colleagues is by far the most controversial.

    The idea here is to utilize the known properties of ES cells—which can contribute to, and possibly create, all major tissues and organs—combined with the ability of an oocyte to reprogam somatic nuclei. Individually, each of these technically difficult steps had been shown to be feasible. It had been shown that human ES cells can be derived with efficiencies that approach 30 percent or so, and that somatic nuclear transfer can be used to generate viable cloned offspring in multiple species. During his time at Advanced Cell Technology Inc., Dr. Cibelli had also shown that blastocysts can be derived from enucleated eggs that harbor somatic nuclei, and he had shown that parthenogenetic embryos can generate ES cell lines in primates (as had been shown with other species decades ago).

    The present paper has put all of these technologies together for the first time using human blastocysts, human somatic nuclei, and deriving a viable ES cell line. The results are not entirely unexpected and are in keeping with the cautions echoed by scientists as to efficiency and economic feasibility. A single ES line was obtained from approximately 250 blastocysts and, interestingly, the single line obtained was using somatic nuclei from the same donor. Rather than constituting a novel breakthrough, the success of Moon et al. is likely attributable to their ability to obtain a large number of healthy blastocysts (this helped overcome the low success rates of this procedure), and perhaps to their strategy for removing the oocytes’ genetic material.

    Even if this method can be made routine, efficient, and legal, two issues come to mind when considering its potential use for transplantation. One is time. The entire process of generating, characterizing, and analyzing ES cells takes time. Amplifying enough cells to obtain the numbers needed for an adult is time-consuming, given the slow cycle times of human cells, plus the ability to direct these cells to differentiate in an appropriate manner is still unproven. Add to that the observation that, while cloned mice may appear normal, subtle errors and differences are present (abnormal weight gain, size changes, aberrant shut-off of genes, etc.), and one could perhaps expect that organs generated after therapeutic cloning may suffer from some of the same issues. This will take time to develop, and to detect. People generally need tissue/organs/repair on an emergency basis, and it is not yet clear if the process could be accelerated.

    The second issue is cost, and cost of competing alternatives. The cost of harvesting blastocysts, performing nuclear transfer, generating a line, and subsequent media costs for maintaining such a line can rapidly add up such that, while technically feasible, it may simply not be economically viable. It is useful to note that most companies have not yet figured out a way to make even a garden-variety stem cell therapy economically feasible, let alone customized cell replacement. Of course, if this was the only option, it is possible that there would be a market for it. However, if competing alternatives to such a therapy were available, then it is unlikely to see a great demand. For example, few people are willing to pay to bank and store their own blood, while most are perfectly willing to use a cheaper, competing alternative (matched blood). Similar possibilities/choices exist in this case as well. They include developing a bank of ES cell lines, making universal donor lines by knocking out the immune locus in an existing ES line, strategies of immune tolerization, and development of novel suppressive therapies. While each of these have their own caveats, they represent at least plausible alternatives.

    In any case, it appears to me that this result is a technical tour de force. It illustrates how rapidly progress can be made when tools and techniques (pioneered across different countries) become readily available and information is shared (note authors across continents). I do not, however, expect this to change anything in the short run. In the long run, I believe additional breakthroughs are required before one considers such a strategy the best way to go. Parenthetically, I would suggest that this should not alter the debate on human cloning (in terms of the scientific landscape). This report does not render human cloning more or less feasible.

    View all comments by Mahendra Rao
  5. It is very sad to hear that the data presented in the paper has been fabricated. One can only speculate that the author might have lost his good judgment as a result of extreme competition and expectation by the people and the nation. I hope this incident will not harm the advance of stem cell research.

    When I read this paper, I questioned why the authors used both the egg and the cumulus cells from the same person, and whether the cloned ES cell is fully functional as a normal cell, as I commented before. Unfortunately, my predictions proved real and the human clone did not exist. I believe attempts of making human clones may be continued, and someday it may be accomplished. However, we have to be very careful when we evaluate the outcomes. This distressing incident gave us an important lesson.

    Now may be the time to put more attention to the use of adult stem cells, which is my current main focus. Using this technology, we may be able to isolate stem cells from a patient, modify them, and transplant them back to the patient. The autologous stem cell therapy may eliminate technical and ethical issues associated with ES cells.

    View all comments by Kiminobu Sugaya

References

News Citations

  1. Not Quite a Dolly, But It's a Human Clone
  2. Personalized Stem Cells Make Debut
  3. Senior Author Requests Retraction of Cloning Paper

Paper Citations

  1. . Dogs cloned from adult somatic cells. Nature. 2005 Aug 4;436(7051):641. PubMed.

External Citations

  1. conclusion
  2. Science website
  3. expression of concern
  4. http://www.sciencemag.org/cgi/content/full/311/5759/321b

Further Reading

No Available Further Reading

Primary Papers

  1. . Patient-specific embryonic stem cells derived from human SCNT blastocysts. Science. 2005 Jun 17;308(5729):1777-83. PubMed.
  2. . Evidence of a pluripotent human embryonic stem cell line derived from a cloned blastocyst. Science. 2004 Mar 12;303(5664):1669-74. PubMed.