정상적으로 발달하는데 실패한 복제 배(embryo)들이 연구와 치료적인 사용을 목적으로 하는 줄기 세포(stem cell)들의 소스(source)로 제공될 수 있다고 개구리를 이용한 새로운 연구 결과들에서 밝혀졌다. 그러한 사실은 영국의 연구진들에 의해서 발표되었다.
Failed Clones May Provide Stem Cells: Study
The results of a new study in frogs suggest that cloned embryos that fail to develop normally may offer a source of stem cells for research and-- possibly --therapeutic uses, British researchers say.
The embryos do not have the ability to form a new organism, but they appear to contain stem cells, the "master" cells that are highly valued because they have the potential to become many different types of adult tissue.
The findings suggest it may be possible to use "very abnormal" human embryos that would die within a few days to establish lines of stem cells, study author Dr. John B. Gurdon, of the University of Cambridge, UK, told Reuters Health.
"Research on human cells could be very valuable in determining the best conditions for making human embryo cells proliferate and differentiate," Gurdon said. It is possible, according to the UK researcher, that cells isolated from defective embryos could have therapeutic uses.
Since these abnormal embryos are not able to survive, "it should be ethically acceptable to use their cells" whether the abnormal embryos are formed by cloning or during a failed attempt at in vitro fertilization, Gurdon said.
The aim of "therapeutic cloning" is to create an embryo that would not develop into a person but that would be a source of "tailor-made" stem cells for a specific patient, reducing the risk of rejection if the cells were transplanted to treat disease.
However, this scenario is controversial for a number of reasons. Many fear that allowing such embryos to be created would be a "slippery slope" that could lead to abuse of the technology. If such an embryo was transferred into a woman's uterus, it could develop into a human clone--a concept abhorrent to most scientists, ethicists and others.
However, Gurdon and colleagues at Wellcome Cancer Research UK Institute in Cambridge studied embryos that did not have the capability to develop into the adult organism.
According to a report in April 30th issue of the journal Proceedings of the National Academy of Sciences (news - web sites), the investigators removed the genetic material from a frog cell and inserted it into frog eggs from which the DNA had been removed. As usually happens in cloning experiments, most failed to develop into normal embryos. Right now, no more than 6% of cloning attempts in animals result in live births. In the 94% of cloning attempts that fail, the cell that receives a nucleus transplanted from another cell either fails to start dividing or become abnormal and eventually die.
At this point, Gurdon's team took cells from the failed embryos and grafted them to frog embryos that were developing normally. Unlike the cells in the normal embryos, the cells from the failed cloned embryos contained a fluorescent gene. The researchers found the protein expressed by the fluorescent gene in several tissues in adult frogs including muscle, skin and backbone cells.
The discovery (news - web sites) suggests that abnormal embryos, despite their inability to develop normally, contain cells capable of forming a variety of specialized cells, according to Gurdon and his colleagues.
Although the experiments were conducted on frog embryos, Gurdon said that cloning research has produced similar results in frogs and mammals. "We therefore suppose that our conclusions will be applicable to human cells," he said.
To test this hunch, Gurdon and his colleagues plan to see if they can achieve similar results with adult skin cells in people.
SOURCE: Proceedings of the National Academy of Sciences 2002;99:6059-
출처: Reuters Health
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