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Is this the end of the debate for human embryo research?

Two landmark papers published this week have demonstrated that stem cells (“Induced Pluripotent Stem Cells”) capable of developing into a wide range of different tissues can be made from human skin cells. It has been claimed in some quarters that this breakthrough will end the debate about the use of embryonic stem cells.

This news comes fast on the heels of the successful generation of stem cells from cloned monkey embryos, discussed in this blog last week (see also Raffaela Hillerbrand’s post), and was anticipated in the weekend papers by the news that a pioneer in cloning research had decided to move his research efforts into the same work on “induced pluripotent cells”.

But is this discovery really likely to end the ethical debate about research using human embryos?

The debate about the use of stem cells in research has revolved around two key issues. The first relates to the potential medical benefits to be gained from the use of stem cells. The second relates to the source of those cells.

Since the discovery that certain cells in the body were not committed to one particular function, but were able to develop into different specialised tissues, it has been speculated that these stem cells could be used to replace or regenerate damaged or diseased tissue. A large number of different illnesses have been cited as possibly being amenable to treatment with stem cells. The potential benefits seem almost limitless, and some of the emotional force of the debate has been driven by the impassioned pleas of those afflicted by incurable injury or illness.

The problem has been that such stem cells are found particularly in early embryos, and that obtaining them usually involves the destruction of the embryo. This has led to heated debate about the moral status of early human embryos, and whether the potential benefits of the research justify their use in this way. Opponents of such research (including the current US administration) have looked for alternative sources of stem cells (for example so-called “adult stem cells”). Much debate has revolved around whether adult stem cells were likely (or as likely) to yield the promised benefits of embryonic stem cells.

The new research is important in that it shows that stem cells can be made from adult skin cells, and that these behave in important ways like their embryonic versions. It may be that the use of embryos is unnecessary to generate the sort of therapeutic benefits that are proposed.

However there are several reasons to think that it is premature to announce the end of the debate about embryonic stem cells.

Firstly it is important to note that the “induced Pluripotent stem cells” (iPS cells) are not identical to stem cells sourced from embryos. The process of inducing the change in the skin cells so that they behave as stem cells involves the use of a retrovirus which activates a number of genes. These genes allow the cell to keep dividing, and tell it to lose its specialized characteristics (of a skin cell). However these same sort of genes are activated in a number of cancers, and it may be that the use of such cells would be associated with a real risk of malignancy. (In addition the use of retroviruses can also induce other minor genetic changes in the cells, whose consequence are so far unknown) So it is important to keep an open mind about whether or not embryonic stem cells might be safer for use in therapies than iPS cells.

Secondly, at this stage only a limited range of in vitro tests have been performed using the new cells. It is possible that embryonic stem cells will be better able to differentiate into the tissues that are needed for treatments.

Third, there are likely to continue to be good reasons for performing research in human embryos – even if stem cells can be safely and efficiently generated from other sources, and they prove as effective in treatment. For example, such research may be necessary for the development of therapies for a range of genetic diseases not amenable to stem cell based treatment. As I alluded in my post last week, it may be that research using early human embryos is ethically preferable to research in animals, since it will not cause the research subjects to suffer, and research findings are more likely to be directly transferable to humans.

The debate isn’t over yet.

Further reading
American Journal of Bioethics blog
Induced Pluripotent Stem Cell Lines Derived from Human Somatic Cells (Paper by James Thomson’s team in Wisconsin, published in Science)
Induction of Pluripotent Stem Cells from Adult Human Fibroblasts by Defined Factors (link to pdf version of paper by Shinya Yamanaka’s team, published in Cell)

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