Scientists have created cloned embryonic stem cells using the nuclear material of adults. They did this by using somatic-cell nuclear transfer (SCNT), the same technique which produced Dolly the sheep. With this technique, all the genomic DNA is from the cloning target, while the mitochondrial DNA is from the egg donor.
In 2005, Hwang Woo-suk rose to infamy when he claimed to have cloned the first human embryos, only to have it turn out to be faked. (As an aside, I find it galling that he still has an active lab.) Since then, researchers have successfully created cloned human embryos, with he caveat that their source DNA came from fetal and infant cells. While a great feat for creating embryonic stem cells, this limits the therapeutic and cloning potential of their technique.
Now, scientists have successfully created cloned embryos using DNA from adult humans, specifically from the skin. Out of 77 donated eggs, they were able to successfully create two embryonic cell lines with the potential to grow into multiple cell types. Interestingly, the most successful cells came from two particular egg donors, suggesting that there is some variable within the oocyte that determines cloning success.
Therapeutically, this has a lot of potential. A patient can have embryonic stem cells created using DNA from the skin, and then used to repair damaged tissues, regrow organs, etc. This is a bit similar to induced pluripotent stem (iPS) cells, where skin cells are re-programmed back into stem cells. Both techniques have the advantage of using cells from the patient, removing the risk of immune rejection. It would be interesting to test how cloned embryonic stem cells compare to iPS cells, and whether there are advantages such as increased genomic stability or ability to differentiate.
Finally, the biggest implication is that it's now theoretically possible to take DNA from an adult, and create a cloned embryo. Now these reported cloned embryos weren't implanted and allowed to develop, since that would be pretty ethically crazy. While we don't know for sure whether they have the ability to form a full-formed human, it's plausible. At the minimum, it's just a matter of honing the technique to get to that point.
What do you guys think? Do we have anything to gain from cloning a full human? Is it just a matter of time before someone attempts this?