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WASHINGTON– Despite ethical issues raised by mitochondrial replacement therapy and uncertainties about the potential risks, women with serious mitochondrial diseases appear willing to accept these unknowns for the chance to prevent transmission of the diseases to their biological children.
Mitochondrial replacement therapy (MRT), which was recently granted approval in the United Kingdom, involves removing the nuclear DNA from the egg or fertilized egg of a woman with mitochondrial abnormalities and inserting it into a donor egg with normal mitochondria, after the nuclear DNA of the donor egg has been removed.
An MRT technique that entails removing the mitochondrial DNA from the intended mother’s egg is being evaluated at two centers in the United States, the University of Oregon, Eugene, where it has been performed in macaque monkeys, and the New York Stem Cell Foundation.
Courtesy Wikimedia Commons/Archaeogenetics/Creative Commons License
The possibility of mitochondrial DNA replacement has generated significant controversy.
The technique, also known as mitochondrial donation, mitochondrial transfer, or mitochondrial DNA replacement, has generated significant controversy, with critics warning that it will lead to “germline enhancements,” eugenics, and designer babies.
But at a 2-day meeting sponsored by the Institute of Medicine (IOM), researchers presented survey data showing that for women who are carriers of these mutations, the ethical concerns are secondary.
In a survey of 92 women who were known carriers of a mitochondrial DNA mutation or were at risk of carrying a mutation, there was universal concern about transmitting mitochondrial DNA mutations to their children, and “overwhelming support and widespread interest” in the clinical use of MRT, particularly among women considering having children at the time of the survey, according to Dr. Michio Hirano, professor of neurology at Columbia University, which collaborates with the New York Stem Cell Foundation on this research.
Almost 80% of the women said they had considered not having children because of the transmission risk and almost three-quarters of those who already had children said they would have considered not having children if they had known they carried the mutation.
Carrying a mutation “has a profound effect on what these women think about their progeny and the risk of transmitting disease,” said Dr. Hirano, who is codirector of the North American Mitochondrial Disease Consortium.
Almost all of the 21 women who were considering having children at the time of the survey said that having a biological child was “very” or “somewhat” important to them, and almost all said they would be interested in the option of MRT. Dr. Hirano, noted that preimplantation genetic diagnosis (PGD), an option often raised as an alternative to MRT, is not always reliable.
Kirah Fasano, a 32-year-old with chronic progressive external ophthalmoplegia, who spoke at the IOM meeting, said that because of her type of mitochondrial disease, PGD was not an option, and after several failed attempts with in-vitro fertilization using her own eggs, she and her husband opted for an egg donor.
She now has a healthy baby, but MRT “is exactly what we would have been looking for,” she said. “I would do it today if it were available,” even after hearing the potential downsides of the technology, she added.
Heather Ward, who has MELAS (mitochondrial encephalopathy, lactic acidosis, and strokelike episodes) and whose daughter was diagnosed with the disease at 18 months, acknowledged that children do bear risk with new techniques such as MRT. But she said that risk must be weighed against the benefits of potentially preventing neurodegenerative mitochondrial diseases in those children.
“It’s very important, if we have the option, to be able to give mothers with MELAS the option to have healthy children. We have the technology. We need to study it,” she said. “And I think it’s a huge disservice to women who have this disease to not give them that option.”
But another meeting participant, Marcy Darnovsky, Ph.D., said that there are two applications of these technologies – human reproductive cloning and human germline modification – which “are so dangerous from a safety and a social standpoint, that they should be taken off the table.”
These genetic techniques should not be evaluated as a medical treatment, where the medical risks are weighed against the medical benefits, because they do not provide a medical benefit but “a very real social benefit,” the ability to have a genetically related child, said Dr. Darnofsky, executive director of the Center for Genetics and Society, in Berkeley, Calif. While the desire of parents should be taken seriously, “they don’t trump everything else,” she added.
Other topics discussed during the meeting included whether egg and sperm donors view themselves as parents, the importance of a direct genetic connection to one’s child, and the concept of procreative liberty. The participants also discussed the unknown risks of manipulating the mitochondria, how to follow-up with children born as a result of MRT, and the risks to young egg donors paid to donate.