For the first time, scientists have achievedhuman “therapeutic cloning,” creating human embryos through cloning and extracting stem cells that were thenmorphed into other kinds of cells.
The stunning announcement, being made today by South Korean scientists at a major American science conference in Seattle, boosts hope for stem-cell therapies for diabetes, Parkinson’s disease, spinal cord injuries and other diseases — though such treatments remain years away.
The news is also certain to ratchet up the ethical debate over cloning.
Others have claimed success at human cloning, including a biotech company, a Kentucky researcher and a religious sect. But scientists have largely dismissed those declarations because they were not reviewed by their peers and published in major journals.
The unprecedented research, by a team from Seoul National University, is being reported in today’s edition of the journal Science, published by the American Association for the Advancement of Science, which is meeting in Seattle.
The South Korean group’s work goes beyond basic cloning to producing viable stem cells from the embryos, essential to developing potential therapies.
“I’m staggered,” said Gerald Schatten, a University of Pittsburgh researcher who has been trying to accomplish the feat in monkeys. “This means we’re in a new era of medical promise for generating embryonic stem cells for treating diabetes, spinal cord injury and Parkinson’s disease.”
Many researchers applauded the findings, but some cautioned that scientific, financial and ethical hurdles remain, putting clinical trials of embryonic stem-cell treatments at least five years away.
Jose Cibelli, a cloning and stem-cell researcher at Michigan State University who helped the Korean team verify the findings, said therapeutic cloning has been accomplished in cows and mice, but few scientists realized anyone was close to achieving it in humans.
“When I first saw their manuscript, I almost passed out. This was it,” Cibelli said. “This paper proves that you can take a cell committed to being one type of tissue and make it go back in development. This is the first time it was done in humans.”
Stem cells are primordial cells that can theoretically develop into all of the body’s 220 cell types — possibly replacing damaged or defective cells — but exactly how they can be coaxed into desired cell types and ensured to function properly in a patient largely remains to be seen.
“Embryonic stem-cell research is still at the Wright brothers’ stage,” said Arthur Caplan, a biomedical ethicist at the University of Pennsylvania. “This shows that it’s possible to get into the air, but it’s not a jumbo jet.”
The Korean team, led by Woo Suk Hwang — a veterinarian who has cloned pigs and cattle and has tried to clone a tiger — collected 242 eggs from 16 women who signed consent forms and were not paid.
After removing the genetic material from the eggs, the researchers said, they inserted cumulus cells — which nurture developing eggs in the ovary — from the same women into their own empty eggs.An electric pulse fused the genetic material from the cumulus cells with the eggs.
After about five days, early-stage embryos known as blastocysts formed with more than 100 developing cells, including stem cells, along the inner wall of the blastocysts. The researchers removed the stem cells and grew them into other basic kinds of cells in a lab dish. They also injected some stem cells into mice. After six weeks, those stem cells became skin, muscle, bone, cartilage and other specific kinds of cells, the researchers said.
Cell therapy hopes
Michael Manganiello, senior vice president at the Christopher Reeve Paralysis Foundation, said the development is especially hopeful because the cumulus cells and egg cells came from the same women. That could lead to cell therapies that wouldn’t cause immune system rejection, he said.
“The idea that someone with spinal cord injury could essentially cure themselves without having to take immune-suppressant drugs is a wonderful potential of this discovery,” he said.
Several scientific obstacles must be overcome before therapies are realistic, said Arlene Chiu, a program director at the National Institute of Neurological Disorders and Stroke in Bethesda, Md., one of the National Institutes of Health.
It’s one thing to inject stem cells into a patient with a spinal cord injury and hope the cells become Motor neurons, Chiu said. It’s quite another to make sure the cells go to the right place, become the right kind of cell and connect with the right network.
“If some of the cells form aberrant circuits, will they cause adverse events like seizures?” Chiu asked.
Steve Stice, a cloning and stem-cell researcher at the University of Georgia, said regulators are concerned that stem cells injected into patients could turn into benign but grotesque-sounding tumors called teratomas — a dynamic mass of dozens of different cell types, from teeth to kidney to brain.
“It’s pretty evident that stem cells will be effective, but the question of safety may take the most time to answer,” Stice said.
The Korean experiment also raises questions of cost, Stice said. The team from Seoul collected 242 eggs to produce one active stem-cell line. In the United States, procuring a single egg costs about $3,000.
“The cost is going to be way too prohibitive for most patients,” Stice said.
Another issue is access to stem cells. Under a 2001 decision by President Bush, federal funding for stem-cell research is limited to the 78 stem-cell lines in place at the time, four of which were created by Stice and his colleagues.
But only 15 of those stem-cell lines have proven useful so far, said James Battey, chairman of the NIH Stem Cell Task Force. In 2002, the NIH awarded just $11 million in grants for embryonic stem-cell research, with $170 million going to research on adult stem cells, which some scientists say are promising but not as malleable.
The new study also reignites ethical issues, experts say. The Korean women donated eggs specifically for research, not for any potential reproductive benefit for themselves. In the United States, stem-cell research has primarily involved leftover eggs from fertility clinics, where the original intent of collecting eggs is to have babies.
“We may need to analyze whether eggs should be taken for nonreproductive purposes,” said Schatten, of the University of Pittsburgh.
Abortion opponents also raise concerns. By discarding hundreds of embryos to get one stem-cell line, the researchers abused human life, said Richard Doerflinger with the U.S. Conference of Catholic Bishops.
“This is creating new human life solely to destroy it, and in an especially wasteful way,” he said.
The U.S. House of Representatives has approved a ban on cloning for reproductive or therapeutic purposes. The bill has been bogged down in the Senate, where supporters of therapeutic cloning want to prohibit only reproductive cloning.
In December, the United Nations delayed a decision on whether to ban cloning for at least a year, after a debate over an all-out ban vs. a partial one. The United States urged the United Nations to prohibit both varieties.
By DAVID WAHLBERG
The Atlanta Journal-Constitution
Published on: 02/12/04