Top four list: why embryonic stem cells are critical   Conklin
says he'd never be able to carry out his iPS work without
advances made with embryonic stem cells. Here's his list:  1)
Scientists have genetically engineered embryonic stem cells that
are widely used for studying specific processes in the lab.
"Obviously, we can remake those cells lines using iPS cells but
it's a huge waste of time," he said. Instead of making progress
toward developing new therapies or finding new drugs, labs would
have to spend years redoing work they've already done.  2)
Embryonic stem cells are farther along clinically than iPS cells
or the new directly reprogrammed cells. "The first clinical
trials of pluripotent cells will be embryonic stem cells. Ten
years from now we'll probably see a mix of embryonic and iPS
cells," he predicted. Adult cells are good for many things, he
said, but aren't as flexible as pluripotent embryonic or iPS
cells.  3) Embryonic stem cells reproduce the steps taken by
nature. "The idea is that natur