Two alternative methods of deriving embryonic stem cells came a step closer to reality today. Will the debate about embryonic stem cell sources continue?
One: The single blastomere approach.
Bob Lanza and his colleagues at Advanced Cell Technology, a company in Worcester, Massachusetts, US, overcame this problem in mice by extracting just one cell from a very early 8-cell embryo called a morula. Lanza and his colleagues coaxed the single extracted cell, called a blastomere, into dividing into a colony of ESCs.Two: Altered nuclear transfer.
They did this by putting the blastomere in contact with pre-existing ESCs. These provided the correct signals for the blastomere to become a stem cell too.
The second technique, dubbed “altered nuclear transfer” or ANT and developed by Rudolf Jaenisch and Alexander Meissner at the MIT’s Whitehead Institute in Boston, Massachusetts, overcomes a slightly different ethical objection, that of extracting ESCs from transient cloned “embryos”.These two methods will allow some people to sleep easier at night -- increasing the pressure on Monsieur Bush to ease his Embryonic Stem Cell restrictions -- but will it be enough?
These are created from a patient’s “donor” cell, a skin cell for example, merged with a human egg emptied of its own nucleus. This forms an embryo similar to that from which Dolly the cloned sheep was produced, and has the potential to provide an exact tissue match for the patient.
The objection to this, again, is that an “embryo” capable of becoming the twin of the patient if implanted into the womb has to be destroyed in order to obtain the ESCs needed to treat the patient.
Jaenisch and Meissner got round this in mice by infecting the “donor” skin cell with a virus. This blocks the action of Cdx2, a gene essential for formation of the placenta. Only then was the skin cell merged with an egg, creating an entity unable to be implanted in the womb, and therefore not “qualifying” as a true embryo.
We shall see.
mumble: dedifferentiation, aka transdifferentiation aka nuclear reprogramming rocks!