A member of the “lobby group Comment on Reproductive Ethics” maintains that there are “some scientists who like to hold on to what they’ve got, but” she doesn’t “think people are going to waste time on embryonic stem cells any more.”
(Josephine Quintanelle, quoted in the Guardian, 3/1/09)
The American Medical Association sends its members a “Morning Rounds” email with the latest headlines on science and medicine. The articles have more links than my posts and the editors seem to choose that days’ big story.
Today’s big story is that the Washington Post (free registration required) reports on a from a Letter to the journal, Nature. Two groups of scientists, one from Toronto (Andras Nagy, from the University of Toronto) and another from Edinburgh (Dr Keisuke Kaji, at the Medical Research Council Centre for Regenerative Medicine at the University of Edinburgh) have found a way to make skin cells transform into embryonic-like stem cells without using viruses.
This should lead to a cheaper way for people to have their own cells transformed into therapies. Farther down the line, it could help us treat disease and injury -and aging – in place, by inducing repair where it’s needed and without transplants. On the other hand, if we use embryonic stem cells, it would be necessary to make a clone of each person or find some sort of universal donor cell that would not be rejected. The previous way of reprogramming cells to an embryonic stage used viruses that could not be removed and which have the potential to cause cancer if left in the DNA of the cells.
The scientists used human fibroblasts – a type of skin cell – which were treated with a “jumping gene” from a cabbage looper moth, that inserts itself into chromosomes along with the genes that “reprogram” the fibroblast — then, the extra gene can be removed.
From the Post, a very clear description.
The alternative cells, known as induced pluripotent stem cells, or iPS cells, appear to have many of the same characteristics as embryonic stem cells but are produced by activating genes in adult cells to “reprogram” them into a more primitive state, bypassing the moral, political and ethical issues surrounding embryonic cells. Until now, however, their use has been limited because the genetic manipulation required the use of viruses, raising concerns the cells could cause cancer if placed in a patient. That has triggered a race to develop alternative approaches.
“These viral insertions are quite dangerous,” Nagy said.
In the new work, Nagy and his colleagues in Toronto and at the University of Edinburgh in Scotland instead used a sequence of DNA known as a transposon, which can insert itself into the genetic machinery of a cell. In this case, the researchers used a transposon called “piggyBac” to carry four genes that can transform mouse and human embryonic skin cells into iPS cells. After the conversion took place, the moth gene, called “piggybac” lost its ability to insert itself into the chromosomes of the cells and “disappear” or can be removed.
“PiggyBac carries the four genes into the cells and reprograms the cells into stem cells. After they have reprogrammed the cells, they are no longer required, and in fact they are dangerous,” Nagy said. “After they do their job they can be removed seamlessly, with no trace left behind. The ability for seamless removal opens up a huge possibility.”
Unfortunately, for some reason the scientists used (non-stem) fibroblast cells from embyros as the cells that are reprogrammed, so the research is being repeated in cells from non-embryonic sources.