In 2007, the world was introduced to induced pluripotent stem cells (iPSCs).
With this breakthrough, Somatic Cell Nuclear Transfer (SCNT) -- more commonly known as cloning -- suddenly looked to be the Dodo bird in the field of stem cell research and regenerative medicine.
But human cloning for research has staged a mini-comeback recently, attended by the usual media hype that always seems to accompany any development in embryo-destructive stem cell research.
In a 10/6/11 article published in Nature, scientists reported that they had, for the first time, successfully generated a line of stem cells from a cloned human embryo.
Numerous media outlets hailed the news as a “major breakthrough” for stem cell research that had, according to CBS, “scientists buzzing.” “May lead to cure for Parkinson’s and diabetes” declared the (London
But for all the buzzing and talk of cures on the horizon, the stem cells harvested from the cloned embryo were therapeutically useless. Dr. Scott Noggle, co-author of the Nature article announcing the “breakthrough” admitted as much: "These cells are not therapeutically relevant at the moment," he stated. The cells were, in fact, abnormal, given the way that Noggle and his colleagues carried out the SCNT procedure.
Typically, the SCNT procedure entails removing the nucleus from an egg, thus removing its genetic material. The nucleus from the donor’s somatic cell is then inserted into the enucleated egg and stimulated to begin development of the cloned embryo. This is the process used to create Dolly the sheep, but it has never been successful in producing a viable human embryo.
The success reported in Nature changed this procedure by inserting the nucleus of the donor’s somatic cell into an intact egg, i.e., an egg that still contained its nucleus. While viable (for purposes of harvesting stem cells) embryos were produced, because the egg’s nucleus was not removed the embryos were abnormal, as they contained an extra set of chromosomes, as did the stem cells harvested from those embryos. Thus, the cells could serve no therapeutic purpose. "These are grotesquely abnormal cells, so they have no clinical applications. Even scientifically they are of questionable value," said Maureen L. Condic, an associate professor of neurobiology and anatomy at the University of Utah
In truth, news of this supposed “breakthrough” came across as tired and stale, especially in light of the fact that scientist are currently producing patient specific, fully pluripotent stem cells without having to create and destroy embryos -- iPSCs .
IPSCs are ordinary somatic cells, such as a skin cell, that have been reprogrammed into a fully pluripotent state, like an embryonic stem cell. Among the great benefits of this breakthrough in reprogramming cells is that it gives researchers a ready and virtually unlimited supply of pluripotent stem cells without having to destroy human embryos. Nor would women be subject to health risks and exploitation because of the large number of eggs necessary for research cloning.
Moreover, iPSCs are patient specific, i.e., they share the same genetic material with the donor of the reprogrammed somatic cell. For many, the ability to generate patient specific stem cells for transplant was the holy grail of stem cell research. The whole point behind cloning for research was to generate such cells by using SCNT to create an embryo that was the virtual genetic duplicate of the patient, and then destroy that embryo for his or her stem cells.
With the advent of iPSCs, cloning for research became all but obsolete. No less than Ian Wilmut, the scientist most associated with cloning for his role in creating Dolly the sheep, announced he was giving up on SCNT research to pursue iPSC research instead. And the California Institute for Regenerative Medicine, established by voter referendum in 1997 with a 10 year, $3 billion budget and a mandate to give preferential funding to human embryonic stem cell research (hESCR), including cloning for research, has been noticeably stingy in grants given to the latter (in fact, the number of grants CIRM has given over the years to adult stem cell research projects has proven greater than those for hESCR and SCNT).
No doubt the idea of cloning will continue to provide fodder for science fiction writers and their fans well into the future. And it will keep some researchers buzzing.
But the supposed potential of human cloning for research to be a practical, therapeutic tool to actually help treat patients, already seems like a thing of the past.
