Reprogrammed adult stem cells may not be as useful an alternative to controversial embryonic stem-cell research as had been hoped, researchers found in two articles published Monday.
Researchers at Children’s Hospital Boston and Johns Hopkins University published an article online in the prestigious journal Nature finding that such adult stem cells remain fundamentally different from embryonic stem cells and are no better at curing diseases in mice.
Many in the medical community and among pro-lifers have hoped harvesting embryonic cells, which destroys the days-old human embryos and has provoked intense ethical and moral criticism, could be avoided if scientists could manipulate adult cells to act as if they were embryonic stem cells.
Called “induced pluripotent stem cells” (or iPS), the altered adult cells “forget” they were once cells naturally “programmed” to become liver cells, lung cells, skin cells, etc. This would make them, theoretically, as useful as embryonic cells for a variety of miracle cures, especially for degenerative diseases such as Alzheimer’s.
It turns out, the studies say, that they don’t forget.
“Our data indicate that nuclear transfer [from embryonic stem cells] is more effective at establishing the ground state of pluripotency than factor-based reprogramming [of adult stem cells], which can leave an epigenetic memory of the tissue of origin that may influence efforts at directed differentiation for applications in disease modelling or treatment,” the article’s findings stated.
A second, separate group of scientists led by Konrad Hochedlinger, a stem-cell biologist at Massachusetts General Hospital Center for Regenerative Medicine, published similar findings Monday in Nature Biotechnology. That group said the adult cells obtained from mice exhibited distinct patterns that could not be erased.
Kitai Kim, a postdoctoral fellow and one of the leading researchers on the project published in Nature, explained that older cells are more set in their ways and difficult to reprogram. His group worked with mice, reprogramming different kinds of cells with varying results.
The needed DNA change “was incompletely reset in [reprogrammed adult] cells compared to nuclear-transfer stem cells,” said co-senior author Andrew Feinberg. “This paper opens our eyes to the restricted lineage of iPS cells. … The lineage restriction by tissue of origin is both a blessing and a curse. You might want lineage restriction in some cases, but you may also have to do more work to make the iPS cells more totally pluripotent.”
Those who oppose using embryos for stem-cell research have long argued in favor of replacing them with adult stem cells. Critics have argued that embryonic stem cells are scientifically superior to adult stem cells. And the researchers said the findings demonstrate that the scientific focus needs to be on embryonic stem-cell research.
Arthur Caplan, director of the Center for Bioethics at the University of Pennsylvania, said the results of the study weren’t surprising from a scientific perspective, but could still have enormous implications for future research.
“A giant balloon of enthusiasm just got the air let out of it,” said Mr. Caplan.
“What this shows is that ideology and values are no substitute for science,” he said. “The science on this is still early, and the values and moral beliefs are going to have to wait until the science has told us what’s possible.”
Debi Vinnedge, executive director of the Children of God for Life, which opposes using embryonic stem-cell research, said the study wasn’t particularly helpful in resolving moral issues surrounding stem-cell research because both types of cells start with the aborted fetus.
“From a moral perspective, there’s no difference between embryonic and reprogrammed adult stem cells because scientists used embryonic stem cells and/or aborted fetal cell lines in order to accomplish the reprogramming,” Ms. Vinnedge said.
The research did show, however, that while reprogrammed stem cells may not be as versatile as embryonic ones, they can still be quite useful.
Thousands of patients around the world have been treated with adult stem cells, but no humans as of yet have been given cells derived from embryos in an approved trial.