Bill, a poster at GetReligion.org has responded to my second post regarding embryonic stem cell research. Fearing that our playful repartee might be cut off by the GR powers that be, Bill was kind enough to post here at Bioethike (see Bill’s comment under previous post). Privately, I’ve promised Bill a response. Here goes:
Bill: Robert, I think I’ve found the source of the confusion. I gather that, for you, the term SCNT refers to an entire process that, by definition, results in a clone.”
Robert: Bill, I’m working with the definition of SCNT provided by the National Institutes of Health (NIH). Note that SCNT results in an embryo:
Somatic cell nuclear transfer (SCNT)—A technique that combines an enucleated egg (nucleus removed) and the nucleus of a somatic cell to make an embryo. SCNT can be used for therapeutic or reproductive purposes, but the initial stage that combines an enucleated egg and a somatic cell nucleus is the same. See also therapeutic cloning and reproductive cloning.”
Bill: When I first learned the term SCNT from a class, it was presented to me as strictly denoting the act of removing a nucleus from a somatic cell and placing it inside another, enucleated cell (not necessarily an oocyte). In this latter sense, SCNT does not refer to the overall process of cloning (which I oppose), but only to the transfer of a nucleus in general.”
Robert: OK. Must have been an interesting class. If you’re aware of research going on in which nuclei are being inserted into enucleated non-oocytes, I would be interested in reading more about it.
Bill: Consider a hypothetical point in the future in which scientists have learned how to manipulate an enucleated oocyte such that when the donor nucleus arrives, the host oocyte reprograms it to express the genes of a self-renewing target cell, such as an adult stem cell, a progenitor cell, or even something like a pancreatic beta cell. The question is: is this modified-oocyte-plus-donor-nucleus an embryonic cell? I would say no, because it’s gene expression and developmental potency would be nowhere near that of an embryonic stem cell. No blastocyst or embryonic stem cells would result from the division of the cell in question. Such a process would involve literal SCNT, but would not constitute SCNT-cloning because no embryo results from any step in the process.”
Robert: Now I think I understand. You’re confusing types of cells. In layman’s terms, an oocyte is an egg. In your example, in which a nucleus is injected into an oocyte, you are perfectly describing SCNT, which results in an embryonic clone. Embryonic stem cells taking from such a clone in the blastocyst stage of the development would not need to be further developed into adult stem cells. We can harvest adult stem cells already, without destroying embryos, and use these cells therapeutically. In fact, we’ve been doing that for more than 40 years.
Further, I think (hope?) that what you’re trying to support is not “literal-SCNT,” as you coin it, but using Induced Pluripotent Stem Cells (iPSCs), which are artificially created from adult cells and do not require the destruction of embryos, as does ESCR. The iPSC process uses viruses to transfect genes to a non-pluripotent adult cell. Wiki describes the process. This research is occuring now. Again, a definition of iPSCs from the NIH:
Induced pluripotent stem cells—Adult cells reprogrammed to an embryonic stem cell–like state by being forced to express factors important for maintaining the “stemness” of embryonic stem cells (ESCs). Mouse iPSCs were first reported in 2006 (Takahashi and Yamanaka), and human iPSCs were first reported in late 2007 (Takahashi et al. and Yu et al.). Mouse iPSCs demonstrate important characteristics of pluripotent stem cells, including expressing stem cell markers, forming tumors containing cells from all three germ layers, and being able to contribute to many different tissues when injected into mouse embryos at a very early stage in development. Human iPSCs also express stem cell markers and are capable of generating cells characteristic of all three germ layers. Scientists are actively comparing iPSCs and ESCs to identify important similarities and differences.
Bill: I emphatically hope you see that I have tried to be as transparent as possible and am not using any deceit to obscure the situation and smuggle in an immoral practice under the fog of confusion. Above all, I want to honor God by pursuing the truth.”
Robert: I appreciate your transparency and your desire to continue this conversation. Further, as I have caused offense, I ask for your forgiveness for the sake of Christ. By His grace, may all of us join in discovering and proclaiming the truth of the Lord of all Life in this “culture of death.”
Robert, thank you very much for your helpful and enlightening response! I see now that I had been using the incorrect definition of the term SCNT out of ignorance. Since, as you pointed out, the definition accepted by the NIH and companies like CSC involves the creation and destruction of an embryo, please consider me a firm opponent of SCNT.
You wrote: “OK. Must have been an interesting class. If you’re aware of research going on in which nuclei are being inserted into enucleated non-oocytes, I would be interested in reading more about it.”
The class really was quite interesting, but it was way out of my depth. It was an upper-level biology course at Harvard taught in 2006 by a scientist named Douglas Melton, apparently a heavy hitter in stem cell research. Since my earlier comment suggests that I learned an inaccurate definition of SCNT in that class, it’s only fair to point out that I am a physical chemist who knows next to nothing about biology and that I lacked almost every prerequisite required to take the course, so it is entirely likely that Dr. Melton gave the correct definition and I simply misunderstood it.
However, I do remember seeing quite a few examples in lecture of researchers removing nuclei from adult somatic cells and inserting them into other adult somatic cells (definitely not oocytes), which is how I learned of the general procedure of nuclear transfer that I must have mistaken for the specific technique of SCNT. From these lectures, I got the impression that transferring nuclei to non-oocytes was fairly common in research. I think the purpose of those experiments was to answer the questions “what controls the fate of a cell: the nucleus or the cytoplasm?” and “does the cytoplasm reprogram the nucleus or does the nucleus reprogram the cytoplasm?” Apparently, researchers that make iPSCs take advantage of the ability of the nucleus to reprogram the cytoplasm (I took the class just before iPSCs made their debut, so I did not learn of them at the time). If you look at my hypothetical example of the pancreatic beta cell transplant, my suggestion there was to harness the ability of the cytoplasm of a beta cell to reprogram the nucleus of a somatic cell. The former technique is obviously a remarkable way to produce pluripotent stem cells and, as you point out, holds a lot of therapeutic promise without requiring the destruction of an embryo. I suspect the latter technique might be better for producing already differentiated cells (like beta cells), since it doesn’t require knowledge of how to direct the differentiation pathway of an embryonic-like stem cell to a beta cell. Having said that, I don’t know if it is currently the subject of any serious investigation. I wish I had taken better notes in that class so I could point you to some of the research I saw on nuclear transfer between different types of cells.
Robert, I do apologize for my harsh tone in my earlier post on GetReligion and for accusing you of constructing a straw man and using inflammatory rhetoric. Looking back, I can see that, from your point of view, I was you either had to assume I didn’t know what I was talking about (which I didn’t) or that I was using deceit to advocate the destruction of embryos. You acted justly. Please forgive me for responding rashly.
“By His grace, may all of us join in discovering and proclaiming the truth of the Lord of all Life in this ‘culture of death’.” – Amen!
Bill, I rejoice in God’s gift of Absolution: given and received. Please drop again when you have a chance!