Ready.
researchers use a micropipette to remove the nuclear DNA of a human oocyte.
Oregon Health Sciences University
With the help of changes in in vitro fertilization (IVF) techniques, researchers are one step closer to finding a way to prevent mitochondrial diseases that can cause a variety of potentially fatal disorders. These techniques have been shown to work in monkeys but now scientists say they have successfully transferred the DNA of a human egg cell with mutant mitochondria to another without these mutations, producing embryos can grow for several days and give rise to embryonic stem cells. The technique is very effective, however, and he is ready to try in patients.
Mutations in mitochondria, organelles that produce energy in a cell and perform their own DNA, can cause a range of symptoms, including heart failure, dementia, and blindness. The severity and symptoms may vary, but they tend to affect tissues with high energy requirements, such as the heart, muscles and brain. There is no way to treat the disease. Because mitochondrial DNA (mtDNA) in embryos mainly comes from the oocyte or egg, several groups of researchers have worked to find ways to prevent the condition using modified IVF techniques, which would allow women who wear mutations chance of conceiving children with healthy mitochondria.
One technique that worked in monkeys is called transfer pin. Researchers eliminate the nuclear DNA which represents the vast majority of genetic information from an unfertilized egg cell which carries mutant mitochondria. Then, they transfer the DNA into an egg from a healthy donor, from which the nuclear DNA has also been removed. The result is a egg carrying the nuclear DNA from the patient and healthy mitochondria egg donor. In 09, Shoukhrat Mitalipov, reproduction biologist at Oregon Health & Science University, West Campus in Beaverton, and colleagues have shown that the technique could produce healthy baby monkeys. Today, they report online Nature they used the technique with human eggs, showing that it can produce normal embryos looking statements.
It does not work as well as it does in monkeys, however. Only about half of the manipulated egg cells developed normally after being fertilized, much less than standard IVF techniques. The researchers managed to obtain embryonic stem cell lines six spindle transfer embryos. Analyzing the mitochondria of stem cells, they were able to whether the mitochondria were transferred along with nuclear DNA. They found that less than 1% of mtDNA resulting in cells derived from the donor cell DNA, a rate Mitalipov said is probably sufficient to prevent disease.
The technique has raised ethical questions, as the progeny carry the genetic material from three different sources: the nuclear DNA from the mother and father, as well as the mitochondrial DNA of the egg donor . Because every girl child born after the technical pass mtDNA given to their children, the technique is a kind of stem cell therapy. The term refers to genetic changes which would pass on to future generations, and experts agree that it requires further review. However, an ethics group of leading UK said earlier this year that the technique is justified as a means of preventing an otherwise incurable disease.
The new result is promising, says Mary Herbert, a reproduction biologist at the University of Newcastle in the UK who is also working on techniques to prevent mitochondrial diseases. However, she said, the success rate is worryingly low. Before the technique could be used to treat patients, she said, researchers need to know much more about the potential health of the resulting embryos. She and her colleagues are working to develop tests to assess better how the embryos produced with such techniques are comparable to conventional IVF techniques. "It is an ethical imperative," she said, that potential patients have enough information to assess the benefits against the possible risks of using technology.
Mitalipov said he and his colleagues are in contact with the US Food and Drug Administration to determine what information would be needed before clinical trials could proceed.
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