Wednesday, May 15, 2013

Somatic Cell Nuclear Transfer Used to Create Human Embryonic Stem Cells

A international team including scientists from Oregon Health & Science University and the Oregon National Primate Research Center have just announced in Cell that they have successfully used somatic cell nuclear transfer (SCNT) to develop human embryonic stem-cell lines. As I understand the paper, the team removed genetic material from the core of multiple oocytes from two different human donors, and replaced it with nuclear material taken from the skin cells of an embryo. Some portion of the eggs from each donor then proceeded to develop to the blastocyst stage, at which point their cells were plated and tested for pluripotency. Pluripotency was proven when the cells, injected into immuno-deficient mice, formed tumors containing tissue- and cell-types representing all three germ layers.This paper, then, is the most powerful proof of principle to date that we may one day be able to combine SCNT and embryonic stem-cell technologies to generate made-to-order, genetically-compatible replacement tissue for humans with diseases such as diabetes or Parkinson's.

It's important to note that the blastocysts were imperfect in various ways, and could not have successfully been implanted into a woman to make a child. (Members of the same team have not yet been able to create a cloned monkey embryo capable of implantation.) This has created some verbal problems that will no doubt be fodder for the culture wars. Strangely, the mostly-liberal National Public Radio is reporting that the scientists created and destroyed human embryos, while the mostly-conservative Wall Street Journal is saying that the team's achievement "is a long way from creating a human embryo."

Here's how I think of it: while the team used cloning technology to create human embryonic stem cells, they didn't exactly create and destroy a human embryo along the way; they created what they knew to be a faulty approximation of a human embryo, but one close enough to the real thing to generate pluripotent human embryonic stem-cell lines. (Think of the fact that human embryonic stem-cell lines can also be generated from parthenotes which are completely incapable of developing into embryos.)

Nonetheless, I'm pretty sure these scientists would have no problem with creating a perfect, and in principle perfectly implantable, human blastocyst--though they have no intention of implanting one, and no research oversight body anywhere would permit them to, even if they did. They want to generate tissue, and if perfecting human embryo cloning helps them do that, they will. Even if you agree with me that the toughest ethics questions aren't quite yet raised by this work, this work certainly implies that they'll be raised sooner or later.


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