Biologists transform skin cells into human eggs in a revolutionary experience

A team of scientists has managed a microscopic thing worthy of Houdini. In new research today, they show that it is possible to create functional human egg cells from a person’s skin cells.

Researchers from Oregon Health & Science University led the study, published Tuesday in Nature Communications. Using a variety of techniques, they managed to fertilize the eggs generated from skin cells, which then grew up in the laboratory for several days. Although the results are only proof of concept for the moment, the method could one day provide a new way of treating infertility if it is fully developed, according to the researchers.

“(F) urgent research is necessary to ensure efficiency and safety before future clinical applications,” they wrote in the document.

Cell reprogramming

Millions of people worldwide are infertile, often due to dysfunctional gametes (eggs or sperm).

In vitro fertilization can help some couples successfully design, but not all, especially people who do not seem to have remaining functional eggs. Ohsu scientists and elsewhere have hypothesized that the other cells of a person can be reprogrammed in an egg or functional sperm using a method called in vitro gametogenesis (IVG). These newly formed gametes could then be used for fertilization as usual (some scientists work on a different branch of abortion, trying to create eggs and sperm from stem cells).

The Ohsu and others team have so far demonstrated that feminine abortion can be carried out with mouse skin cells, but the new study seems to be the first to show that such a process is also possible with human cells.

To create these eggs, the researchers replaced the nucleus of an egg cell with that of a skin cell – a method called nuclear transfer of somatic cells. The method had already been used to create cloned animals, like Dolly sheep.

However, they could not stop there because the healthy eggs and sperm contain only one set of chromosomes, while other cells bear two. Thus, the use of replacement eggs as is for typical fertilization would cause zygotes – fertilized eggs that develop in embryos – with too many chromosomes.

To get around this obstacle, the researchers applied mitomeiosis, a technique intended to imitate the natural process of meiosis. This process helps transform cells with two sets of chromosomes in sperm or egg cells bearing a set, throwing the sets of spare chromosomes.

They generated 82 functional eggs in total. Among these, 9% were successfully fertilized by sperm and developed in a blastocyst, the cell of cells which forms from a zygote about five days in fertilization. Researchers generally study only laboratory embryos until they reach the stage of blastocyst, which is also when doctors generally implant an embryo created by IVF in someone’s uterus.

There remains a lot to overcome

As impressive as the team feat, they warn that the technique is still far from being medically useful.

In addition to the low fertilization rate, surviving blastocysts had many chromosomal anomalies. Other tests have also revealed that even if they have successfully reproduted egg cells with the correct number of chromosomes (23), these eggs probably had vital differences compared to eggs produced naturally.

The reprogrammed eggs did not undergo a cross recombination during meiosis, for example. It is a process where the two sets of chromosomes of a cell on the sides of our mother and our father are mixed to form eggs and sperm which have a set of chromosomes with equipment from both parents (this helps ensure genetic diversity).

In other words, as things arise now, these eggs are unlikely to produce embryos that could successfully become in a human fetus.

“Although our study demonstrates the potential of mitomeiosis for gametogenesis in vitro, at this stage, there remains only proof of concept,” wrote the authors.

However, the work of the team brings them significantly closer to the objective of creating viable eggs from practically nothing. With enough time, research and luck, their technique or something similar could allow certain families to design children that they could otherwise have.