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Stem Cells 2.0


Last November, two teams of scientists announced they had successfully “reprogrammed” adult cells to function like embryonic stem cells without the need for embryos. The advent of these new induced pluripotent stem (or iPS) cells raised the prospect of a truly win-win conclusion to the stem cell debate, in which the scientists can study the pluripotent cells they deem most promising, but without techniques that raise ethical concerns. The immediate response among the political advocates of embryonic stem cell research in Washington was to deny the importance of the work, to insist that embryo-destructive research would continue to be needed, and to keep pushing for taxpayer funding of the use of newly destroyed embryos in research. In the meantime, however, these new iPS cells have begun to take over the field, because they are not only free of ethical concerns, but also far easier and cheaper to derive and use.

This new article in Nature Reports: Stem Cells offers a sense of how excited stem cell scientists are about this work, and how quickly it is moving forward. A few snippets:

The fact that making iPS cells does not pose the technical and ethical challenges of working with eggs or embryos is drawing large numbers of researchers into the field and speeding up reprogramming research. “This is definitely the hot thing right now,” says Melina Fan, executive director of Addgene

“Biologically there’s no difference” between murine iPS and ES cells, says Jaenisch. Both can generate all the tissues in a mouse. Human iPS cells have not been as rigorously demonstrated to be quasi-equivalent to ES cells, and they won’t be, because doing so would require generating human babies or foetuses. Such experimentation is irrelevant anyway, says Douglas Melton, director of the Harvard Stem Cell Institute in Cambridge, Massachusetts, who has derived multiple human ES cell lines. “Nobody’s trying to make people.”

The enthusiasm with which the highest-tier ES cell scientists have turned to reprogramming speaks volumes.

The ten-year head start human ES cells got on human iPS cells has effectively shrunk to zero, says [stem cell pioneer James] Thomson

With the ethical clouds hanging over those procedures lifting, anxieties about funding are receding. A cadre of talented young investigators trained on ES cells and ready to surpass their mentors is chafing at the bit.

No one doubts that iPS cells will eventually be generated from the cells of individuals with known medical history. That was the main advantage claimed for somatic cell nuclear transfer [cloning], a technically and ethically challenging procedure that has yet to be achieved in humans. For generating person-matched cells, iPS cells may be not only easier to use but perhaps superior, as they would share both nuclear and mitochondrial DNA with the original patient, whereas cells derived by somatic cell nuclear transfer carry only the same nuclear DNA.

The politicians will have to catch up eventually.