Hilzoy performs the painful task of reading Charles Krauthammer on stem cells. She writes:
Obsidian Wings: Krauthammer On Stem Cells: Krauthammer gets the science wrong. He writes this about the President's stem cell policy:
It failed practically because that cohort of embryos is a diminishing source of cells. Stem cells turn out to be a lot less immortal than we thought. The idea was that once you created a line, it could replicate indefinitely. Therefore you would need only a few lines. It turns out, however, that as stem cells replicate, they begin to make genetic errors and to degenerate. After several generations some lines become unusable.
In addition, there has been a new advance since 2001. Whereas stem cells in those days had to be grown on mouse feeder cells, today we can grow stem cells on human feeder cells. That makes them far more (potentially) therapeutically usable.
I don't know who the 'we' is who were surprised that when you get DNA to copy itself repeatedly, errors creep in. It certainly wasn't the scientific community, which warned against this from the get-go. The only 'we' I know of who ever thought the President's policy made enough lines available consists of George Bush, Tommy Thompson, and (apparently) Charles Krauthammer. And it's an understatement to say that lines not grown on mouse feeder cells are 'far more (potentially) therapeutically useful' than the lines the President's policy lets people work on, since the latter are almost certainly not usable therapeutically at all. I mean, you could also say that driving a car is a far better way of getting from one place to another than sitting on the ground and saying 'vroom vroom vroom'. It's true, but it rather understates the difference...