Friday, April 1, 2011

What does SCNT create? What is the therapeutic justification for it?

From the Pioneer Press today:
[T]he debate is about therapeutic cloning, which would create cells that are a genetic match of the patient, so the patient might later receive them in a transplant with almost no risk of the immune system rejecting them — a major risk in any transplant today.
This is misleading, for successful therapeutic cloning does not create just "cells," any more than I am merely a (much larger) "collection of cells." Rather, what we are talking about is an organism, a self-integrated whole with the internal resources and active disposition to develop himself or herself (sex is determined) to maturity, given the appropriate environment and nutrition. More specifically, she is a human organism -- a member of our species -- at the earliest stage of development.

Theoretically, the human organism resulting from cloning could then be killed in order to derive embryonic stem cells, which, as the Pioneer Press story notes, could theoretically be used in a patient transplant.

More from the story:
That value [of cloning] lies in how those cells — embryonic stem cells [from cloned human embryos] — can be directed to reproduce other cells in the body, such as heart muscle cells to potentially repair a damaged heart. There are other ways to harvest embryonic stem cells, but SCNT holds the best promise for how to create cells that won't be rejected by the patient — because they'll be genetically identical.
It's true that cloning could solve one of the (multiple) significant problems with embryonic stem cells -- immune rejection. But there is strangely no mention in the story of the induced pluripotent stem cell (iPSC) breakthrough from a few years ago. iPSCs are functionally identical to embryonic stem cells, and they are patient-specific, just like embryonic stem cells from a cloned embryo. There seems to be no difference, except that iPSCs already exist, are easier to use and are less expensive (not to mention they are ethically uncontroversial). That's why Dr. Oz told Oprah in early 2009 that "the stem cell debate is dead." That's why Dr. Ian Wilmut switched from therapeutic cloning to iPSCs.

More from the story:
[University of Minnesota researcher Dr. John Wagner] said critics who say advances in adult stem-cell research are rendering therapeutic cloning irrelevant are mistaken because it's uncertain whether adult stem cells can ever be made to mimic embryonic stem cells and because such a breakthrough, if possible, is "years away."
I'm not sure what Dr. Wagner is talking about, or whether he was misunderstood by the reporter. It's true that adult stem cells are not pluripotent, like embryonic stem cells -- it is actually that extra flexibility that causes embryonic stem cells to form tumors, while less-flexible adult stem cells have successfully treated many different medical conditions.

But if we are looking for pluripotent stem cells that are not embryonic, that breakthrough is not "years away" -- it happened years ago. And it was that breakthrough that caused many, such as former National Institutes of Health head Dr. Bernadine Healy, to say that embryonic stem cells (including embryonic stem cells derived from cloned embryos) are "obsolete."

Meanwhile, with embryonic stem-cell therapies in clinical trials, it could be sooner when a living patient's life or death might hinge on whether therapeutic cloning is legal or not.
True, embryonic stem cells are now in some trials, but they have not successfully treated anyone. Adult stem cells have been successfully treating patients for decades. Moreover, none of the embryonic stem cells in trials were taken from cloned human embryos. No stem cell trials taking place (or that have ever taken place) could have been affected by the bill under consideration, which would merely ban the creation of embryonic human beings by the cloning process known as somatic cell nuclear transfer.

More about the human cloning ban here, here and here.