MONDAY, Jan. 16, 2006 (HealthDay News) -- Stem cells taken from cloned embryos are likely to be safe when used for therapeutic purposes, a new study finds.
"This is actually really good news," said Tobias Brambrink, lead author of the study and a postdoctoral researcher in the (Rudy) Jaenisch lab at the Whitehead Institute for Biomedical Research in Cambridge, Mass.
Although the work, which appears online this week in the Proceedings of the National Academy of Sciences, was done in mice, there is hope the findings will translate to humans.
"This is very encouraging because it says that in mice we don't find any abnormalities, so then it is very likely that the human lines are normal, too, but it is still something that has to be done formally," Brambrink said.
Dr. Louis "Skip" Elsas, director of the Dr. John T. MacDonald Foundation for Medical Genetics at the University of Miami, said he found the research "interesting" yet not "earthshaking."
The technique at issue here is called "therapeutic cloning," or somatic cell nuclear transfer.
Scientists first create a clone by removing the nucleus from a donor cell (perhaps a skin cell), then putting it into an egg that is missing its nucleus. The engineered egg goes on to become an early stage embryo that produces stem cells. Researchers then take the stem cells with an eye to "growing" them into specific, customized cells for cell-replacement therapy.
The hope is that these cells may one day provide treatments or cures for diseases such as diabetes, liver failure, spinal injury, stroke, Alzheimer's disease and heart disease.
"Stem cells hold great promise for human therapy," Brambrink said. "In an optimal world, we would make stem cells genetically matched to a patient."
Therapeutic cloning is the same technique that South Korean scientist Dr. Hwang Woo-suk claimed to have used to clone human embryonic stem cell lines. Just last week, it was announced that the research turned out to have been faked.
The technique has been performed to produce cloned animals, albeit with significant problems.
"Most of the cloned animals through all kinds of species are abnormal," Brambrink explained. "A lot of them die prematurely, or have all kinds of defects. Many cloned mice die immediately after birth because of breathing failure."
Even cloned mice that look normal have turned out to have differences in gene expression when compared to mice derived from fertilized embryos.
The concern is that cloned stem cell lines would exhibit the same or similar problems.
"One of the big concerns is if these stem cells express (produce) genes that can cause cancer. After implanting them into a patient, it would be cancer waiting to happen," Brambrink said. "You want to make sure that the cells you use for therapy are actually normal and are not in any way screwed up to start with."
Many researchers suspected that the cells would be normal. Still, no one was certain and nobody had looked at the molecular evidence.
For this paper, Brambrink said, "we looked at cloned and fertilized embryonic stem cell lines. The question was basically is there any difference on a molecular level between the two."
The researchers took five fertilization-derived stem cell lines and five cloned stem cell lines from different mouse strains, and did a gene-expression analysis for more than 30,000 genes.
"We analyzed pretty much the entire set of genes that can be expressed and we found no significant difference between the two," Brambrink said.
The question of how this might work in humans is still an open one, but scientists say they are apparently a step closer to a happy ending.
"This paper shows that it's worth the effort to clone an embryo and make a stem cell line because it should be useful for therapy," Brambrink said.
On the other hand, the research does not answer the question of what goes wrong in reproductive cloning, Elsas pointed out.
More information
To learn more about stem cells and stem cell research, head to the International Society for Stem Cell Research.
