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Scientists at a little-known California biotechnology company yesterday claimed to have cloned a human embryo theoretically capable of yielding stem cells, but fell short of generating the avidly sought blank slate cells through the process.
The work by Stemagen Corp. won faint praise from top figures in the field, who said that though the assertion appears supported by the research, this provides more evidence that humans can be cloned, like sheep or mice. At least one European laboratory has cloned human embryos, although to a less advanced state using a different process and with less scientific certainty than that described by the La Jolla-based company in the somewhat obscure journal Stem Cells.
The lead scientist at Stemagen, however, called the work an advance toward the goal of creating lines of "true" embryonic stem cells using a process know as somatic cell nuclear transfer, or therapeutic cloning.
"No other scientific group has documented the cloning of an adult human cell, much less been able to grow it to blastocyst stage," said Andrew J. French, Stemagen's chief scientific officer and lead author of the research.
A blastocyst is an embryo about five days old and containing 50 to 200 cells. This is the stage at which stem cells - capable of forming any of the body's 220 cell types, including blood, bone, and nerve tissue - can be harvested for research or therapy, a process that destroys the embryo.
The research drew criticism from religious groups opposed on moral grounds to using embryos for scientific research.
Leading stem cell scientists not involved in the work described Stemagen's research as seemingly solid, but not especially useful since it did not forge stem cells.
"It's very convincing, [it's] just not that big a leap," said Dr. George Q. Daley, president of the International Society for Stem Cell Research and a stem cell scientist at Children's Hospital Boston. "The real holy grail is to generate a pluripotent stem cell line from a cloned human blastocyst. It's only a matter of time before some group succeeds."
The study did demonstrate just how critical is a source of fresh human eggs for stem cell research using embryos. Harvard University, at the international forefront of stem cell research, has been thwarted in its efforts to create stem cell lines through cloning because of a lack of donor eggs since Massachusetts, like other states, forbids paying women to donate eggs for research.
Stemagen says it got around the restriction by acquiring "excess eggs" from fertility clinics, which are allowed to pay substantial fees to women providing eggs for in-vitro fertilization.
French, in an interview, said the controversy surrounding human cloning made the company decide to have its research confirmed by an independent lab - thus, sacrificing the early-stage embryos - rather than risk having its results called into question. The company's next step will be experiments aimed at generating new stem cell lines, or batches, by creating human embryos using a similar process of replacing the nuclei in an unfertilized human egg with DNA from an adult.
"We are already working hard toward that end," said French, a reproductive biologist.
Scientists believe that stem cells may hold the key to curing a huge array of human ailments, from heart disease to severe spinal cord injury. Despite breathtaking recent advances in creating "embryonic-like" stem cells through relatively simple genetic reprogramming techniques using ordinary adult tissue, there is wide agreement among researchers that stem cells obtained from human embryos are necessary for research and possible cures. Human embryonic stem cells have been extracted from unused fertility clinic embryos, but stem cells from cloned embryos are likely to be more useful because they would be genetically matched to a patient whose DNA is used in the cloning process.
South Korean scientist Hwang Woo Suk said in 2005 he obtained stem cells from cloned human embryos, but he retracted the claim after it was revealed much of his research was faked.
Those who toil in the ferociously competitive but also somewhat clubby world of advanced stem cell research said yesterday they know little about researcher French or Stemagen.
"They certainly deserve credit for trying and persistence," said Dr. Robert Lanza, chief scientific officer for Advanced Cell Technology, a Worcester biotech firm that has made several big splashes in stem cell research.
But Lanza called Stemagen's work "underwhelming" and said the resultant embryos "look very unhealthy, at best."
Biologist Douglas A. Melton, codirector of the Harvard Stem Cell Institute, said there was "nothing substantially new" in the research. "We already know it's possible to get a blastocyst from nuclear transfer," Melton said, stressing that the next big leap for the field is generating human stem cells from cloned embryos, not making embryos for the sake of chalking up firsts.
Stemagen, according to the research published in Stem Cells, used 29 eggs from three donors to generate five entities that in French's view might be described as embryos at the blastocyst stage. Testing of mitochondrial DNA, however, showed only a single "proven" clone theoretically capable of generating embryonic stem cells, the research stated.
Not all scientists shrugged off the Stemagen research, noting that it represents the most indisputable cloning of a human embryo to date.
"I think the data are pretty important," said Donald G. Phinney, a stem cell researcher at Tulane University. "This paper takes proof of principle work in nonhuman primates and applies it to humans."
Colin Nickerson can be reached at nickerson@globe.com.
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