— Scientists for the first time have derived thriving colonies of embryonic stem cells from human embryos created using cloning technology.
In experiments documented in an article released today by the journal Nature, a team of scientists from the New York Stem Cell Foundation Laboratory claim they created two lines of the cells through the use of somatic cell nuclear transfer (SCNT), the less emotionally and politically charged term for cloning.
The accomplishment moves science closer to the long-elusive goal of using SCNT – in which an adult cell is fused with an egg and activated to make an embryo — to create stem cells that match patients. Scientists hope the cells could one day be used to treat or even cure diseases like diabetes, and usher in an era of so-called “regenerative medicine.”
But there is an important catch to the announcement. Unlike normal stem cells, the cells obtained by the team also included DNA from the human eggs used in the process, resulting in a highly abnormal 69 chromosomes rather than the usual 46. That makes the cells useless for therapy, but, argued lead scientist Dieter Egli in a press conference with reporters, the cells can be used “to address important questions, like asking how these cells compare to [other stem-like cells]…We now have a reliable assay to build on to conduct future research.”
Larry Goldstein, director of the University of California San Diego Stem Cell Program, agreed that the experiment represents a significant accomplishment.
“It’s not going to lead to a therapy,” he said. “But from a longer term perspective, it is very important.” It will help tease out the reasons why human SCNT has been so difficult.
Dolly the sheep, the first cloned mammal, was announced in 1997 and ever since, science has been trying to make human blastocysts, the embryonic stage at which stem cells can be harvested. A scandal involving a Korean team that claimed to have done it rocked the field when their claim turned out to be fraudulent.
In 2008, a small San Diego biotech, Stemagen, announced that it had created human blastocysts by cloning. A company spokesman told msnbc.com that it has done it twice since. But efforts to derive long-lasting stem cells have failed.
This new experiment appears to elucidate the main problem. Unlike SCNT in other animals that have been cloned, the New York team demonstrated that certain factors in the human egg’s nuclear DNA are required to make resulting stem cells viable.
“When we first removed the [egg] genome and replaced it with the genome of the skin cell, development [of the embryo] arrested after a few divisions,” Egli said. So they left the egg’s DNA in place. That way, whatever gene products that make the difference between survival of embryos and stem cells — what those are haven’t been identified — would still be present.
Gerald Schatten, director of the Division of Developmental and Regenerative Medicine at the University of Pittsburgh School of Medicine predicted this nearly a decade ago. Based on past work of his own, he suggested that it might be necessary to leave an egg DNA structure called the meiotic spindle intact if the embryo was to develop and the resulting stem cells live. In light of this new paper, he wrote in an email, “it is reasonable to conclude that primate eggs (human and non-human alike) differ from mice and other rodents, and also eggs from domestic species” like cows and pigs.
With these new cell lines it should be possible to figure out what those differences are and navigate around them.
The Egli team used skin cells from an adult diabetic and a healthy control. By leaving the egg’s genome intact, the scientists were able to make human cloning about as efficient as animal cloning. They got 13 blastocyst stage embryos from 63 eggs. From those 13, they derived one stem cell line that matched each donor. Analysis proved that the cells were fully reprogrammed by the eggs, giving them a development do-over.
Some had hoped that embryonic-like cells made by manipulating adult cells, so called “induced pluripotent stem cells,” would not only obviate the need for SCNT, but do away with the need for embryos at all. But the cells have shown disturbing characteristics like a tendency to accumulate modifications in cancer-related genes.
But one of the key accomplishments of the experiment isn’t scientific at all, it’s ethical, according to Alan Trounson, president of the California Institute for Regenerative Medicine.
Human eggs are difficult to come by, a fact that Trounson thinks has stymied some research. But the New York foundation asked female patients of Columbia University’s IVF program who had already agreed to donate excess eggs harvested during procedures if they would like to divert some of those eggs to research. The reimbursement, $8,000, was the same either way, a strategy, the foundation argued, that negates any charge women were unduly pressured.