When the first baby conceived using a technique that mixes genetic material from three people was born in 2016, scientists expressed concern that the procedure had not been studied enough to prove it was safe. An answer to those still open questions comes with the first comprehensive study in early stage human embryos. Scientists from the ‘Chinese Pla General Hospital’ in Beijing led him. Based on the results obtained, the authors report that the procedure does not seem to affect the development of these embryos.
The technique of using the DNA of 3 people to create embryos, aimed at preventing mothers with defects in the mitochondria – the organelles that supply energy to cells – from transmitting them to their children, would therefore be safe.
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“Mitochondrial replacement therapy is a controversial field,” says the study co-author Wei Shang, obstetrician and gynecologist of the ‘Chinese Pla General Hospital’ in Beijing. “With our research, we hope to provide a basis for the development of the technique.” Shang and colleagues studied the safety of one of the three main types of mitochondrial replacement therapy: spindle transfer, used to give birth to the first baby with genetic material of 3 people, born in Mexico in 2016. In this method, nuclear DNA egg from a woman with defective mitochondria is transferred to an egg taken from a donor with healthy mitochondria to which nuclear DNA has been removed. The egg is then fertilized with the father’s sperm in a test tube. The resulting embryo contains genes from both parents and mitochondrial genes from the donor.
As part of the study, the team compared dozens of human embryos undergoing spindle transfer with embryos from a control group. Scientists had them developed up to a week after fertilization. And they found that 5-day-old blastocyst cells in both groups had nearly identical levels of gene expression and transcription, suggesting that spindle transfer does not appear to affect early embryonic development. The authors reported their findings in ‘Plos Biology’ last month.
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