Three-person embryos are intended to help mothers with mitochondrial disease from passing it on to their children, but a new study indicates that some faulty mitochondria might occasionally make it through the mitochondrial replacement therapy process, Nature News reports.
During the nuclear transfer process, some original maternal mitochondria are sometimes carried over, but they typically become outnumbered by the replacement, healthy mitochondria. But a study appearing in Cell Stem Cell this week from investigators at the New York Stem Cell Foundation Research Institute found that sometimes that original maternal mitochondria actually outcompetes the healthy replacement mitochondria to become dominant.
"It would defeat the purpose of doing mitochondrial replacement," senior author Dieter Egli from the New York Stem Cell Foundation Research Institute tells Nature News.
Mitochondrial replacement therapy was legalized last year in the UK, though Nature News notes that the agency overseeing the procedure has yet to allow it. In the US, meanwhile, a National Academies of Sciences, Engineering, and Medicine panel has said that clinical trials of the approach should be pursued.
Based on his team's findings, Egli also suggests caution. While he says that there are likely ways around this issue, until then "I don't think it would be a wise decision to go forward with this uncertainty."