Scientists have successfully changed skin cells into embryonic stem cells, marking the first time human stem cells were cloned by transferring the nucleus of another cell.
Researchers at Oregon Health & Science University and the Oregon National Primate Research Center (ONPRC) were able to create embryonic stem cells, which are valuable for research because they can be turned into any other cell type found in the body. Stem cells provide a way for scientists to look into replacing cells damaged through injury or illness or give them a way to treat different conditions through stem cell therapy.
"A thorough examination of the stem cells derived through this technique demonstrated their ability to convert just like normal embryonic stem cells, into several different cell types, including nerve cells, liver cells and heart cells. Furthermore, because these reprogrammed cells can be generated with nuclear genetic material from a patient, there is no concern of transplant rejection," Shoukhrat Mitalipov, a senior scientist at ONPRC, said in a press release. "While there is much work to be done in developing safe and effective stem cell treatments, we believe this is a significant step forward in developing the cells that could be used in regenerative medicine."
The research was published online in Cell on May 15.
The researchers employed a method called somatic cell nuclear transfer (SCNT), where the nucleus of a skin cell -- the part of a cell that contains DNA -- is implanted into an egg cell that has had all of its genetic material scraped out. What's left is an unfertilized egg cell (with a skin cell nucleus), which then produces stem cells that can develop into many different types of cells found in the body.
Researchers were able to accomplish this because they found a way for the egg cell to stay in the "metaphase," a stage in the eukaryotic cell cycle where the chromosomes that carry genetic information are in the middle of the cell. This preparation step occurs right before the cell is split into two cells. By keeping the cells in metaphase, the researchers were able to scrape out the existing DNA and implant the skin cell's DNA much easier.
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Dr. George Daley, a Harvard stem cell scientist who wasn't involved in the study, lauded the advance in science but pointed out to NPR that is likely to raise debate about the topic of cloning again.
However, because this method doesn't use fertilized egg cells, it is able to provide a middle ground for scientists without angering people who are opposed to using cells that can theoretically develop into fetuses.
Also, while this method can create cloned stem cells, known as therapeutic cloning, it probably will not be able to create full human clones, which is known as reproductive cloning. The researchers pointed out that we are far from that day, especially since related monkey studies have not produced a viable monkey clone. Also, human cells are very fragile, and may not be able to withstand the reproductive cloning process.
"Our research is directed toward generating stem cells for use in future treatments to combat disease," Mitalipov pointed out. "While nuclear transfer breakthroughs often lead to a public discussion about the ethics of human cloning, this is not our focus, nor do we believe our findings might be used by others to advance the possibility of human reproductive cloning."
Robin Lovell-Badge, head of developmental genetics at the MRC National Institute for Medical Research, said to The Guardian that research like this legitimizes the work of therapeutic cloning as a scientific tool instead of something to be feared.
"It is an unsafe procedure in animals and it will similarly be an unsafe procedure in humans. For this reason alone it should not be attempted," said Lovell-Badge. "We are not just a product of our DNA, which is the only thing that is copied in cloning. Nurture and environment are at least as important in determining who we are, therefore cloning cannot be used to bring back a loved one."
Dieter Egli, an investigator at the New York Stem Cell Foundation, told TIME that he was impressed with the results. Egli was not involved in this study, but he was involved in cloning studies with human cells in 2011. He was able to produce human stem cells then, but they had twice the number of chromosomes.
"I think this is a really important advance," he said. "I have a very high confidence that versions of this technique will work very well; it's something that the field has been waiting for."