Scientists have finally succeeded in using cloning to create human embryonic stem cells, a step toward developing new medical treatments but one that might also hasten the day when it will be possible to create cloned babies.
The researchers, at Oregon Health and Science University, took skin cells from a child with a genetic disease and fused them with donated human eggs to create human embryos that were genetically identical to the child. They then extracted stem cells from those embryos.
The embryo-creation technique is essentially the same as that used to create Dolly the sheep and the many cloned animals that have followed. In those cases, the embryos were implanted in the wombs of surrogate mothers.
The Oregon researchers did not implant their human embryos and said they had no intention of doing so. They say that their technique, in any case, probably would not lead to the birth of a viable baby. The same technique, tried in monkeys for years, never resulted in the birth of a cloned monkey, they said.
Nonetheless, the fact that the scientists were able to get cloned human embryos to survive long enough for stem cell extraction is likely to be seen as a step on the way to human reproductive cloning.
The researchers, who published a paper on their work in the journal Cell, say their goal is what has been called therapeutic cloning: making embryonic stem cells that are genetically identical to a particular patient.
Embryonic stem cells can turn into any type of cell in the body, like heart cells, muscles or neurons. That raises the hopes that one day the cells will be turned into replacement tissue or even replacement organs to treat a host of diseases.
Human embryonic cells are now mainly derived from embryos created by fertilization in fertility clinics. But tissues created from those stem cells would not genetically match a patient, meaning steps might be needed to prevent rejection.
Scientists have been trying for more than 10 years to create human embryonic stem cells using the cloning method but have been stymied. Korean researchers made international headlines in 2005 when they claimed to have done this, but the claim turned out to be fraudulent.
Still, the demand for therapeutic cloning may be less now than it was a decade ago because scientists can now use adult skin cells to create a stem cell very similar to embryonic cells, but without the need for embryos. These are called induced pluripotent stem cells.
This article originally appeared in The New York Times.