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Salvaged Cloned Embryos Could Be Rich Resource for Stem Cells


British researchers say cloned embryos that are destined to die could be a rich source of stem cells. Stem cells are master cells in the body that could be used to treat disease.

Most cloning researchers pay attention to the successes, the baby animals that are exact genetic copies of the animal that donate the cells to create them. But in a recently published paper, the authors note they are among the very few researchers to pay attention to dying embryo clones.

Scientists make clones by completely removing the contents of an egg cell and inserting the nucleus, or genetic material, of the creature they wish to copy. The donor DNA directs the growth of the egg cell. For reasons scientists do not understand, cloned embryos fail to make it about 94 percent of the time.

Researchers at Wellcome Cancer Research Institute in Cambridge worked with cloned embryos made from tadpole intestines. Senior researcher John Gurden says the tiny balls of cells began to look irregular almost from the start. These embryos will normally die within 24 hours because they are very abnormal from the start," he says.

Professor Gurden says researchers took healthy cells from the ill-fated embryos and grafted them on to normal frog embryos, much the same way that gardeners graft tree limbs. Investigators also marked the cells from the cloned embryos with a fluorescent tag so they see what would happen.

What occurred were cells from the abnormal embryos, with a little coaxing, became muscle tissue within the fabric of the growing frog embryos. Although the cloned embryo would have died, you can salvage from it not only living cells but cells that have a… substantial prospect of differentiating normally into things like muscle and skin. And also we showed they lived for a very long time, a hundred days or more, says Mr. Gurden.

Researcher John Gurden says the next step is to see whether adult skin cells which are plentiful can become other types of tissue.

Mr. Gurden would eventually like to see the technique applied to humans. If this same approach does apply to humans can be made to work with humans then it means you could take defective human embryos that could not survive and salvage cells from them, which would be very useful for research and might eventually be useful for cell replacement," he says.

Most stem cell researchers support the cloning of human embryos as a source of the highly prized cells. Researchers believe they may be able to treat or cure diseases such as diabetes and Parkinson's disease with a fresh supply of cells from human clones.

President George Bush strongly opposes the cloning of human embryos, declaring that "life is a creation, not a commodity." Mr. Bush is calling on the U.S. Senate to ban all human cloning.

But Stefan Moisyadi of the University of Hawaii's Institute for Biogenesis Research says scientists would not have to use healthy eggs for their work. "The President has said that he does not want to create a trade on human eggs," he says. "And he is afraid that people will be selling their eggs to profit so their eggs will be available to do this kind of work. But I think he is not correct on that because there are a lot of eggs that are used today, and wasted in a lot of ways, in fertility clinics where they are deemed not desirable for fertility work and they are destroyed. Those eggs could be used to produce embryonic stem cells."

Of course, so far it is only a theory that vibrant stem cells could be produced from cast off human eggs and dying cloned embryos. If nothing else, it is likely to add a new wrinkle to the heated debate on human cloning.

The paper on research to salvage dying cloned embryos and reap stem cells is published in "Proceedings of the National Academies of Science."

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