Report of the Formation of Human Embryonic Stem Cells from Single Cells Extracted from 8-10-cell Early Human Embryos Last week’s report by researchers from Advanced Cell Therapies1 describes the formation of human embryonic stem cells from single cells extracted from 8-10-cell early human embryos. Extraction of one single cell at that stage of early human development is nowadays routinely performed for preimplantation genetic diagnostic screening. This screening method is used to test for the presence of genetic problems such as those resulting in cystic fibrosis or other severe genetic diseases. If no problems in the DNA of the extracted cell are found, the remaining intact embryo can be implanted, according to standard in vitro fertilization procedures, in the mother’s womb for pregnancy and the birth of a healthy child. The same group had already reported the formation of mouse embryonic stem cells using such cell extraction procedures earlier this year.2 This technology is feasible because at very early stages of development each and every cell of the embryo is in theory individually capable of giving rise to a healthy adult. In fact this is the principle underlying the birth of identical twins, triplets and quadruplets, all of which come from the same single fertilized egg. Using the technique optimized in preimplantation genetic diagnosis of gently removing one single cell without destroying the rest of the embryo, the authors gently removed every single cell from the embryos. Using all the cells of the embryo allowed them to enhance their chances for success. In the laboratory, one often starts with everything one has, before optimizing the technique to what one really needs. Thus, all the cells were cultured further to obtain human embryonic stem cells, yielding only 2 cell lines out of 91 single cells cultured. It is not clear at this stage why the yield was so low. It could be for biological reasons that not every single cell of the embryo can give rise to embryonic stem cells, or it could be a question of not sufficiently optimized culture techniques, or a combination of both. Only time and repeated trial and error will tell. Foot Notes 2. Chung Y, Klimanskaya I, Becker S, Marh J, Lu SJ, Johnson J, Meisner L, Lanza R (2006). Embryonic and extraembryonic stem cell lines derived from single mouse blastomeres. Nature 439:216-9. Authors Suzanne Kadereit, PhD Posted October 16, 2006
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