Select Committee on Science and Technology Minutes of Evidence


Examination of Witnesses (Questions 40-59)

DR LYLE ARMSTRONG, PROFESSOR CHRIS SHAW AND PROFESSOR AUSTIN SMITH

31 JANUARY 2007

  Q40  Dr Iddon: Chris Mole and I would like to direct a series of questions now to Professor Shaw and Dr Armstrong. Can you convince us that this line of research will be effective in producing embryonic stem cells. What evidence is there?

  Dr Armstrong: There is the evidence from the Chinese Group that I mentioned earlier and, although their experiments have never been repeated, the publications that they have produced are reasonably convincing to my mind that we would be able to produce embryonic stem cells from these lines. Although I have never attempted this in humans obviously, we have some very encouraging data from my laboratory for interspecies embryos between mouse and cow and mouse and rabbit which suggest very strongly that it will be possible to derive embryonic stem cell lines of those species using this model system. We are in the process of proving that the foreign genome which you introduce into these cells is actually becoming active in expressing all of the genes from, say, a mouse as opposed to the cow genes and we believe very strongly that that is happening, that the genome is becoming active and that we will be able to derive embryonic stem cell lines from those.

  Q41  Dr Iddon: So, you are relying really on the work of one group.

  Dr Armstrong: No, not on one group, there are several other groups in China with whom we are in contact, in Beijing.

  Professor Smith: One of course has to acknowledge that this is research. If we already knew that it could be done, we would not be debating Of course, we cannot be certain but it is a real possibility and people like Lyle should be entitled to investigate this and make progress.

  Q42  Dr Iddon: As you know, those people who are concerned about this line of research, which includes the pro-life groups, of course, who will be opposing you in your requests, know that researchers in Japan have been able to wind back adult cells and make them pluripotent. Why is this proposal and the research more advantageous than that claim, if it is true?

  Dr Armstrong: We should really become involved in both of those angles of research. My group in particular are very interested in finding chemical means of inducing pluripotency in somatic cells and I also have some very interesting data looking at how we can interfere with several enzyme systems which are responsible for maintaining what is called the epigenotype of a somatic cell, and that is essentially what we are resetting when we do a nuclear transfer experiment. The trouble is that nature does it so much better than our very clumsy attempts to interfere with that system so far and the work you referred you from Japan from Professor Yamanaka's group has shown that the expression of certain genes which are involved in maintaining the identity of an embryonic stem cell are capable of reprogramming it to an extent but, in order for that reprogramming to be stable, they always have to keep expressing these genes in a very particular format which would be fairly useless from a medical standpoint because you would never be able to transplant cells derived from those cells into a human patient. So, we need to understand what is the actual process that those cells are going through either by the nuclear transfer or cloning process or the reprogramming ideas that Professor Yamanaka was developing or the ideas that I am developing in my group before we can ever start to produce embryonic stem cells on an industrial scale, if you like. It is not the only angle that we can use but it is a very good and very adaptable technical system that we can use to investigate these points.

  Professor Shaw: There are two points. One is that we fully support adult stem cell research and would be delighted if we could take somebody's skin cell and turn it into the neurons that we are interested in studying in terms of the diseases of interest. If you look at where we are at the moment, that line of adult stem cell research has been very poor. People have been working on this for a very long time, from much more accessible tissues and adult stem cells have been available for much longer. Very few nerve cells can be grown from adult stem cells. Nobody has ever made a specific sort of nerve cell such as a motor nerve cell. We know the chemical composition that is required to make a motor nerve cell from embryonic stem cells, so embryonic stem cell technology is working. Adult stem cell technology is way behind that and is not currently working in the same way. I think that both tracks should be pursued but certainly I think the fact that adult stem cell research may show potential is not a good reason to inhibit embryonic stem cell research.

  Q43  Dr Iddon: When we have a cow's embryo being inserted with human material, we are told that that embryo is more than 99% human. Would you all agree with that?

  Professor Shaw: Absolutely.

  Dr Armstrong: Yes.

  Professor Shaw: The mitochondria genome is tiny. There is only 13 polypeptides in the human mitochondria genome that make proteins. In a mitochondria itself, there are probably something like 1,500 different proteins. So, even you want to call these cow/rabbit mitochondria, 99.9% of that mitochondria is actually human and most of the protein that makes up that entity is actually human material.

  Q44  Dr Iddon: The other day we had a seminar with some of your colleagues who work in this area and I was quite surprised because I did not know that in the human embryo that is created, the nucleus can put out into the cytoplasm some of its own mitochondria. I thought that cytoplasm just carried the mitochondria that had come from the donor, be it a cow. Is that accurate or am I mistaken?

  Professor Shaw: Most nuclear transfer that is done is to put the whole cell into the enucleated egg. So it takes with it not only the nucleus, carrying the chromosomes, but also the mitochondria that sit in the cytoplasm. So the human mitochondria are going to be in there as well as the recipient rabbit or cow mitochondria.

  Q45  Dr Iddon: So, in the cytoplasm, there is going to be some interaction between the two, the mitochondria derived from the two sources, and everybody says that the mitochondria and the cytoplasm are the energy producers of the cell but are we sure about that? Can the mitochondria not affect the development of this cybrid embryo in some way and affect the chromosomal behaviour in the nucleus? Are we sure about the role of mitochondria or do we need to do more research?

  Professor Shaw: We cannot be absolutely sure that animal mitochondrial genes will not influence cell function so I think that we should be doing those experiments. I think they are important to do. If you have functioning human chromosomes and you have functioning human mitochondria, most of the machinery will work. You are asking a question as to whether the animal mitochondria would interfere with that process but, until you have actually asked that question biologically, it is difficult to answer. There are experimental ways of attacking that and I think we should be doing that. Because we do not know the answer is not a justification not to use these cells.

  Q46  Dr Iddon: To make a statement—and let us be quite sure about this—that mitochondria are not important in the production of the embryonic stem cells that were producing stem cell lines might not be an accurate statement.

  Professor Shaw: I do not think that anybody said they were not important. It is whether it is a critical issue, this will tell us whether these cells will be of use or not.

  Dr Armstrong: Just to get back to that, I think that the comment I made earlier that they are not critical to the formation of embryonic stem cells is probably true because, at the stage of development we are talking about, the cells are not relying so heavily on the energy generated by the mitochondria, they tend to rely on another process known as glycolysis. It may become an issue when you ask those cells to differentiate into something which does require large amounts of energy derived from mitochondria such as a muscle cell or a nerve cell, but we will not be able to answer those questions unless we perform the experiment in the first place.

  Q47  Chris Mole: Professor Shaw and Dr Armstrong, some of the written evidence we have had has raised concerns about risks associated with this work. Have you carried out an assessment on what those risks might be?

  Professor Shaw: What sort of risks are you talking about?

  Q48  Chris Mole: I am asking you what you consider they might be. Some of the evidence we have received raised concerns about new diseases and diseases crossing the interspecies barrier.

  Professor Shaw: All cells that have been derived from humans are treated in a very special way. All the manipulation done on these cells is done in a protective hood so that the people doing the experiments are not exposed to the cells of and animal origin. That is part of routine laboratory practice. I think that these cells will never be used to be implanted into anybody, which means that there is no risk of any cross-species contamination. We are not using these cells for transplantation and they would not be appropriate for transplantation. They would never be legally allowed to be used for transplantation and that is not the purpose of our experiments. I think that the risk is extremely low in that context. All the risk is as using any human cell, we have to take precautions that we do routinely in the laboratory. We use human cell lines all the time.

  Q49  Dr Spink: I would like to come in on that. Some of the groups have argued to me that this will not work, that it will not give us useful information because it is a hybrid and therefore we should not be doing it, to which I argue back, "If it does not work, then you have nothing to worry about, have you?" How would you answer that?

  Professor Shaw: There is no obvious biological reason why it should not work. Cells with defective mitochondria are present in many different conditions and indeed there are people who carry mitochondrial defects who are perfectly healthy. I see patients who do have mitochondrial-based diseases and that is when the majority of their mitochondria have this gene defect and certain cell populations fail because of that. It is a very, very different situation if the vast majority of mitochondria are defective. I think that is a very clever misinterpretation of the facts.

  Chairman: I want to finish this session by 10.40, so I ask that we all try to be as succinct as we can be with our questions and I ask that you try to be as succinct as possible with your answers.

  Q50  Dr Harris: Would you explain to us what a chimera test of pluripotency is.

  Dr Armstrong: A chimera test is something that we cannot do with human embryonic stem cells because it would involve putting a pluripotent ES cell into the blastocyst of the remaining species such as a mouse and seeing if those cells can contribute to the development of that organism. Typically, we would look for coat colour changes in the mouse to see how pluripotent those ES cells were. We could dissect the mouse to see if the cells derived from those embryonic stem cells were present in all of its internal organs or tissues, but we do not do that with human ES cells. That is the one test we cannot make because it involves mixing a chimera between an animal and a human. It is something we would restrict only to mice.

  Q51  Dr Harris: If you have a stem cell—and I think this applies to a stem cell derived from an adult cell as much as it does to an embryonic stem cell—and you want to check whether it is capable of contributing to all the potential tissue types, that it has that potential before you direct it to one particular tissue type, isn't what you would like to do in a chimera test of totipotency and pluripotency is to put that cell into an animal model which has the same gestational timeframe in order to give the embryonic human cell chance to show what it can do and then see whether it does give rise to those different cell types.

  Dr Armstrong: We can test total potency or pluripotency in a much simpler way simply by injecting embryonic stem cells either into the kidney capsule or into testes with immuno-deficient mice and then specialised types of tumours called teratoma will grow and those can be sectioned and stained for various different types of cells and tissues, and that is the standard we use for determining pluripotency in human embryonic stem cells.

  Q52  Dr Harris: It was suggested to us in the examples from some of your colleagues that at some point you would want to go beyond the teratoma testing towards chimera testing in order to demonstrate totipotency. I definitely remember it being said that that would be a useful step. Do you dispute that?

  Dr Armstrong: To determine total potency is an entirely different matter.

  Q53  Dr Harris: Or pluripotency?

  Dr Armstrong: Because we would have to then determine that the cells were capable of germ-line transmission which I do not think we would want to do in a mouse. A mouse producing human eggs or human gametes would be a little odd, I think.

  Q54  Dr Harris: Professor Shaw, are you interested—?

  Professor Shaw: It is not my area of expertise and it is not my area of interest and I would not want to comment.

  Q55  Dr Harris: We were told that it might be useful to have this chimera test of some kind. If that is the case—and I can see that you are not agreeing with that and we can go back to our source to check, but let us accept that it might be useful in order to test these ES cells—does that create a problem for the 14 day limit?

  Dr Armstrong: The embryo would not be grown in culture, it would have to be implanted into the uterus of some mammalian species in order for it to develop beyond the 14 day limit and then, if such entities did successfully implant and were allowed to grow to term, then we would expect to see contribution from human cells to those developing foetuses, but what that would tell us . . . I do not know that it would really add to the current pluripotency test information that we have. We are developing much better systems from assessing pluripotency on purely chemical bases looking at the biochemistry of these cells. The test which is traditionally being applied today for human cells, as I have said, is the formation of a teratoma and that has satisfied most of the scientific community to date. I am not sure I can see what additional data we could gain from making a chimera between a human ES cell and a mouse blastocyst, for example.

  Professor Smith: I would like to comment on that. I am really very surprised that scientists have apparently argued that that would be a valuable experiment. I cannot see that there is any useful knowledge to be gained from it. I personally would not defend such an experiment. I think it would be very problematic in terms of public perception. This is to make a primary chimera where you are trying to make a whole animal that is essentially half human and half animal. That is the risk you would take by doing that kind of experiment.

  Q56  Dr Harris: I do not think it was proposed to be half and half, I think they argued that one could introduce stem cells at the blastocyst stage and you would see in uterine development without necessarily going to birth what the contribution was to all the tissue types.

  Professor Smith: But it would still be half and half. I would not rule out that you should never do that experiment, that there might not conceivably be at some point something that you can learn, but I cannot see any question at the moment, and the barrier should be very high for that kind of experiment and you certainly should never let it go much beyond implantation.

  Q57  Dr Harris: Do you think that barrier should be created by primary legislation or by the regulator saying we need to have scientific use for this, and even then we would look at it very closely?

  Professor Smith: I would say regulation. One does not know what might happen and how things might change.

  Q58  Adam Afriyie: I want to look at some of the controversy surrounding the ethics and morality, preferably confined to this area of chimeras, hybrids and so on, and, secondly, the controversy surrounding the HFEA's decision to postpone or delay their decision making. In the evidence we have received, the Scottish Council for Human Bioethics said that for those who believe that an early human/non-human embryonic combination is not a person there are no further ethical considerations about the work that is being done. We have had lots of other evidence as well from people saying things like an embryo is a human being from conception, and then of course in this area of hybrids, chimeras, et cetera, there is the question raised by CARE that because these would be unnatural entities created, the barrier between human beings and other species would be blurred. A whole interesting area of morality and ethics has opened up here. Dr Armstrong and Professor Shaw, how would you respond to those ethical and moral objections or considerations in this context?

  Professor Shaw: I think I can understand the origin of the concerns, and obviously human life is extremely important. What is important to do is to put it in the context of what people currently accept as being the role and what is acceptable in dealing with embryos. Many embryos are generated through normal sexual activity, and many contraceptive devices work not by preventing conception but by preventing implantation. The intrauterine device, for instance, prevents implantation, as do many oral contraceptives. There are possibly hundreds and thousands of embryos being created every week that are being destroyed for social reasons. Society thinks that is acceptable and I agree with them. We are able to create embryos for the purpose of deriving cell lines. We create embryos that are not for implantation but are frozen down as part of in vitro fertilisation. If you are going to say that life begins from conception, then the law should apply to all those other embryos and clearly it does not. My feeling is if it is legal to have contraception in this way, and to derive stem cells from very early embryos, then this work falls within that remit. It is almost exactly the same entity as the embryos that are used to derive human cell lines.

  Q59  Adam Afriyie: What about the blurring of the distinction between human beings and other animals or other entities?

  Professor Shaw: I would then revert to the comment that the cells we hope to derive are more than 99.9% human. They are essentially human cells. The embryo that is being generated is essentially a human embryo. I would give you, as an example, the fact that we use animal tissues in many medical contexts, heart valves being the most common one. If you have your aortic heart valve replaced by a pig heart valve, a very common procedure which has happened in this country for more than 20 years, that person does not become a chimera or a hybrid; they are a person with a pig heart valve. These cells are human cells but also have some animal mitochondria.


 
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