Scientists Use Cloning Tech to Swap DNA in Human Eggs

Scientists have adapted cloning technology to create human eggs from skin cells and a donor egg, potentially opening a new route to motherhood for women who are infertile.

The research could one day enable them to have genetically related children by inserting their own DNA into donated eggs, though it is still at an early stage.

Researchers at Oregon Health & Science University transferred nuclei from adult cells to donated eggs from which the nucleus had been removed. They then induced these cells to divide in a way that shed half their chromosomes — a DNA rearrangement necessary for fertilisation.

“In addition to offering hope for . . . people with infertility due to lack of eggs or sperm, this method would allow for the possibility of same-sex couples to have a child genetically related to both partners,” said Paula Amato, OHSU professor of obstetrics and gynaecology.

Reporting their results in the journal Nature Communications, the researchers emphasised that the study was “a proof of concept, and further research is required to ensure efficacy and safety before future clinical applications”.

Shoukhrat Mitalipov, the project leader, estimated that another decade of development would be required before the novel process was ready for use in fertility clinics.

“Clinicians are seeing more and more people who cannot use their own eggs, often because of age or medical conditions,” said Ying Cheong, professor of reproductive medicine at Southampton university in the UK who was not involved in the OHSU study. “While this is still very early laboratory work, in the future it could transform how we understand infertility and miscarriage, and perhaps one day open the door to creating egg- or sperm-like cells for those who have no other options,” she said.

Several research teams around the world including Conception, a California biotech company, and Katsuhiko Hayashi and colleagues at Osaka university are working on in vitro gametogenesis — creating eggs and sperm in the lab.

The others use a different technique that does not require donated eggs, making pluripotent stem cells from skin and then trying to convert them into eggs. This has succeeded with mice but not yet produced mature human eggs, said Mitalipov.

The success of OHSU’s cloning approach, transferring the nucleus between mature cells rather than using stem cells, depended on achieving a new type of cell division called mitomeiosis. “Nature gave us two methods of cell division and we just developed a third,” said Mitalipov.

So far the process is quite inefficient. The OHSU team produced 82 functional eggs that were fertilised with sperm through IVF but only 9 per cent developed to the blastocyst stage at which embryos would be transferred to establish a pregnancy in an IVF clinic. None was cultured beyond this point and there is no evidence that any would have grown into a healthy foetus. In natural reproduction about a third of new human embryos become blastocysts.

“We still have a lot of difficult work ahead to sort out the intricate process by which chromosomes pair and separate to create healthy embryos,” said Mitalipov.