The New Scientist has a good review article that explains a new research report from Robert Lanza of Advanced Cell Technology, that attempts with “thousands” of embryos created by placing human DNA into the oocytes or eggs of animals have failed to produce stem cells. NatureNews, the news arm of the journal, Nature discusses the report, here.
The abstract of the article, “Reprogramming of Human Somatic Cells Using Human and Animal Oocytes” published in Cloning and Stem Cells, is available here. The list of researchers is very long and they are from several different laboratories.
Each of the news articles above includes statements from researchers who do not believe that human-animal cloned embryos are a dead-end for stem cell researchers. However, the confirmation of the outcome from several labs, with different researchers, is strong evidence that it is unlikely that this technique is a reasonable way to produce “patient specific” stem cells – those that are an exact match for the donor of the DNA.
I have not read the actual article, yet, but from the news articles and the abstract, it appears that the “cybrids” do express the genes of the donor DNA and are clones of the donor. However, while enucleated human oocytes are able to reprogram the DNA of the donor to result in embryos that divide to the stage at which it is possible to harvest embryonic stem cells, the emptied eggs of cows and rabbits do not. The cybrids only divide to about the 16 cell stage and do not turn on the genes responsible for pleuripotency, or “stem-cell-ness.”