8 + 1 = embryo + stem cell

The media today are all excited about the “fulfillment” of a suggestion made in the U.S. House in mid-August that stem cell lines could be started by removing a single cell from an 8-cell zygote. It was called a fig leaf at the time—a way to distract people from the techniques for creating embryonic stem cell lines that have been deemed immoral by many. The technique, known as preimplantation genetic diagnosis (PGD) has been used since the early 90s to identify human embryos that have genetic defects. Generally the embryos are from in vitro fertilization (IVF), but they could also be washed from the fallopian tubes before implantation. One or two blastomeres are removed from the developing embryo on Day 3, when it typically consists of 8 blastomeres (cells). The theory is that all 8 blastomeres are genetically identical. If two cells are taken for analysis, each can be checked for genetic makeup, for extra certainty. Many conditions, such as an extra chromosome 21—which will lead to Down Syndrome—can be checked with this procedure. In PGD, “unhealthy” embryos are discarded and one to four “healthy” embryos are introduced into the uterus in hopes that at least one will implant and develop into a healthy infant. The idea of using the extraction technique to establish a stem cell line obviously hasn’t been tested in humans, but today’s news reports mice pups and stem cell lines established using this technique. So, from 8 cells, you take 1; you put the blastocyst (7 remaining cells still clumped together) into a uterus and wait for the pups to emerge. You take the 1 cell and create a stem cell line. Obviously, the numbers are much greater than this. Five embryonic cell lines and 7 trophoblast stem cell lines (the trophoblast is the outer layer of cells of the blastocyst) were created. The baby mice appeared to be normal and healthy. Marie Godfrey, PhD
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