The announcement that researchers were able to create stem cells from adult cells by inserting four genes was big hopeful news back in 2007. Hopeful because such cells would be immunologically compatible transplants for individuals and, more importantly, using induced pluripotent stem (iPS) cells would skirt the fight over the moral standing of stem cells derived from human embryos. A new study published in the current issue of Stem Cells finds that unlike stem cells derived from embryos, iPS cells grow old quickly and die. As Newsweekreports:
Compared with specialized cells produced from the 25 lines of stem cells derived from embryos, those from the eight populations of iPS cells in the study had significantly higher rates of death through a mechanism called apoptosis (which is basically a suicide program within the cells), higher rates of aging (senescence), and severely lower rates of growth. The retinal cells and blood-vessel cells in particular were about as sprightly as cells ready for a nursing home, and lost their crucial ability to continue dividing.
"We just couldn't get the cells to do what we wanted," [Robert] Lanza [chief scientific officer at Advanced Cell Technology] told me. "At first we blamed ourselves, but then we looked at the cell markers and saw that the cells were aging much faster" than true embryonic cells. "There was a 1,000- to 5,000-fold difference" between the iPS cells' ability to keep growing and dividing and the true embryonic cells' ability, he says. "In terms of whether you can use the cells therapeutically or to study disease, that's the difference between getting the study to work and being dead in the water." Other scientists working with iPS cells have begun to see the same problems, Lanza says, suggesting that "this whole population of cells is screwed up."
The Newsweek article notes that some researchers think that maybe this problem can be overcome. (Just a thought - perhaps carefully reactivating the iPS cells' telomerase gene might put off senescence.) The Newsweek article concludes:
... however, "although there is excitement that iPS cells can serve as an embryo-free source of stem cells," says Lanza, "it would be premature to abandon research using embryonic stem cells until we fully understand what's causing these problems." The fight goes on.