>I don’t think that the Scientific Activist (“Reporting from the Crossroads of Science and Politics”) is at all happy with the “framing” of the reports on the reprogrammed adult stem cells. (beware the language)
However, I did learn where some of the speculation about iPS cells being “like an embryo.” may have come from.
“Activist” says that this article from Jaenisch, et al from last summer indicates that the cells are capable of forming embryos and gestating to become a live, born mouse.
Actually, the article discusses the production of chimeras and the production of a viable embryo after the reprogrammed mouse cells are injected into “tetraploid blastocysts.”
A blastocyst is an embryo. So, the Activist and Art Caplan are pointing to different ways to make chimeras, not cells that are unique individuals with an innate self-driven organization – they are not organisms.
In other words, the reprogrammed cells act like embryonic stem cells, but not like embryos – not like the cell that is a zygote – they can’t make the placenta and direct their own organized embryonic development. The iPS (and embryonic stem cells from the inner cell mass) require more manipulation and the innate organization of another organism, the embryo into which they are implanted.
>When you make a chimeric organism, what is it exactly that is alive? Are all the parts derived from the iPS not alive and all the parts from the original blastocyst that are?
>Before the chimera is created, the original embryo is a self-directed and organized organism, while the cell (embryonic or iPS) is not an organism. When the stem cell is added to the embryo, it does become part of the organism. However, it's the fact that the extra step is necessary that makes it okay to scrub off living cells when you bathe or make new cell cultures in the lab (As long as no one – no human individual – dies for it, it's okay.)
>Happy Thanksgiving to you, LifeEthics.Query: In a post below you said something about umbilical cord blood cells being "embryonic-like" and having (if I understood correctly) "similar markers" to the iPS cells. But aren't the cord blood cells multipotent rather than pluripotent? That would seem to make a better case for calling the iPS cells "embryonic-like" and _not_ calling the cord blood cells by that phrase.Am I just wrong about cord blood cells? Are they actually pluripotent? I'm astonished, if so, but it's always better to get these things right, so I'll be glad to be corrected if I've been mistaken about them.