Starting with 25 fresh oocytes, French and colleagues generated five blastocysts–five- to six-day-old embryos consisting of 30 to 70 cells. Rather than attempting to generate stem cell lines from the embryos, the researchers sent them to an independent company for genetic confirmation of their results. “They showed we had completely removed the DNA from the egg donor and replaced it with DNA from the skin-cell donor,” says French. One blastocyst was confirmed as a clone via two DNA-fingerprinting methods, while genetic analysis of two others indicated the likelihood that they were clones.
The next crucial step will be generating stem cell lines from cloned embryos, which many stem cell scientists speculate will be the most challenging step. “That’s likely where Hwang failed,” says Synder.
French and colleagues are planning such experiments, with results potentially in the next eight to twelve months. “The quality of our blastocysts improved with each experiment,” says French. Based on the success rate of previous attempts to make stem cells from regular embryos, he estimates that Stemagen will be able to generate a stem cell line from between five and ten cloned embryos and report the results in the next year. The company aims to sell or license the lines to pharmaceutical companies and others who would use them to test new drugs or develop new therapies.
While human therapeutic cloning has always been an ethically contentious area of research–partly because it requires the creation and destruction of human embryos–it has recently come under greater fire. After the announcement of new techniques for reprogramming adult cells so that they turn into stem cells without first forming embryos, some opponents called for a halt on embryonic-stem-cell research. (See “Stem Cells without the Embryos”.)
However, researchers in the field emphasize the need to pursue all reprogramming techniques. “Even though there are other techniques to reprogram a cell that have gotten a lot of press, we still don’t know how those compare with the reprogramming you actually see with nuclear transfer,” says Snyder. “My feeling is, if we understand nuclear transfer better, we will be able to do the other kind of reprogramming more efficiently.”