There is a disturbing possibility that the new technique may create not stem cells but actual cloned embryos.
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Late last month, Haruko Obokata and her colleagues at the RIKEN Center for Developmental Biology in Kobe, Japan reported that they had discovered a surprising new technique for making stem cells. In a pair of articles published in the journal Nature, they claimed that ordinary mouse cells could be made pluripotent (that is, having the ability to develop into any of the body’s tissue types) by exposing them to various forms of stress, such as acidic conditions.
The most obvious practical application of this new technique is that it could serve as a new source of pluripotent stem cells for regenerative medicine or for research. Initial results suggest that the technique is not only simpler than the genetic engineering techniques developed in 2006 to create induced pluripotent stem (iPS) cells, but also much more efficient at transforming cells to a pluripotent state.
There is still more work to be done before we know whether this procedure will work on the cells of adult humans. There are many differences between the stem cells of mice and humans, and the researchers reported that even in the mice they worked with, using the cells of one-month-old animals was as much as ten times less efficient than using the cells of one-week-old mice. But if it is possible to use this technique on human cells, then it seems to hold real promise as a source of pluripotent stem cells formed without destroying embryos.
The Troubling Potential of STAP Cells
Yet these cells have a troubling potential. One of the surprising features of these cells, which Obokata has called “stimulus-triggered acquisition of pluripotency” cells, or STAP cells, is that they are not only able to develop into all embryonic tissue types—they can also contribute to the development of a placenta. Neither embryonic stem cells nor iPS cells can develop into placental tissue. In fact, this has often been seen as a defining difference between embryonic stem cells and actual embryos: embryonic stem cells cannot, on their own, develop into adult organisms the way an actual embryo can, in part because they cannot grow the extra-embryonic placental tissues needed for fetal development in the womb. If STAP cells can indeed support fetal development, clusters of these cells may actually be embryos. If so, the creation of these cells would be tantamount to human cloning.
Some scientists speculate that these STAP cells could be used for reproductive purposes. In today’s in vitro fertilization (IVF) procedures, egg cells are collected from women, fertilized, and then those embryos are transferred to the mother’s (or a surrogate’s) womb. But in this theoretical new technique, a man or woman could simply have his or her skin cells transformed into STAP cells, which could then be transferred to a surrogate.
If this were possible—and I must stress that it is not clear that it ever will be—then human cloning could become a simple and practical option. One of the most difficult parts of current IVF procedures is acquiring human egg cells, which involves exposing women to potentially dangerous hormones. Even the methods of cloning used to produce Dolly, which have recently been used to clone human embryos, require the collection of egg cells. But this new technique might allow for cloned embryos to be created from just a handful of skin cells, which could be easily and safely collected from either men or women.