Scientists transform skin cells into functional eggs in mice | Top Vip News

New research from Oregon Health and Science University describes the science behind a promising technique for treating infertility by converting a skin cell into an egg capable of producing viable embryos.

OHSU researchers documented in vitro gametogenesis, or IVG, in a mouse model using the preliminary steps of a technique that relies on transferring the nucleus of a skin cell to a donated egg whose nucleus has been removed. Experimenting on mice, the researchers convinced the skin cell nucleus to reduce its chromosomes by half, so that it could then be fertilized by a sperm to create a viable embryo.

The study published today in the journal Scientific advances.

“The goal is to produce eggs for patients who do not have their own eggs,” said the lead author. Shoukhrat Mitalipov, Ph.D., director of the OHSU Center for Gene and Embryonic Cell Therapy.

The technique could be used by women of advanced maternal age or for those who cannot produce viable eggs due to previous treatment for cancer or other causes. It also raises the possibility of men in same-sex relationships having children genetically related to both parents.

Instead of trying to differentiate induced pluripotent stem cells, or iPSCs, into sperm or eggs, OHSU researchers are focusing on a technique based on somatic cell nuclear transfer, in which the nucleus of a skin cell is transplanted to a donated egg stripped of its nucleus. In 1996, researchers used this technique to clone a sheep in Scotland named Dolly.

In that case, the researchers created a clone of one of the parents.

In contrast, the OHSU study described the result of a technique that resulted in embryos with chromosomes contributed from both parents. The process consists of three steps:

• Researchers transplant the nucleus of a mouse skin cell into a mouse egg that has been stripped of its own nucleus.
• Driven by cytoplasm -; fluid that fills the cells -; Inside the donated egg, the nucleus of the implanted skin cell sheds half of its chromosomes. The process is similar to meiosis, when cells divide to produce mature sperm or eggs. This is the key step, resulting in a haploid egg with a single set of chromosomes.
• Researchers then fertilize the new egg with sperm, a process called in vitro fertilization. This creates a diploid embryo with two sets of chromosomes -; which would ultimately result in healthy offspring with equal genetic contributions from both parents.

OHSU researchers previously demonstrated proof of concept in a study published in January 2022, but the new study goes further by meticulously sequencing the chromosomes.

The researchers discovered that the nucleus of the skin cell secreted its chromosomes each time it implanted into the donor egg. In rare cases, this happened perfectly, with one of each pair of egg and sperm chromosomes matching.

“This publication basically shows how we achieved haploidy,” Mitalipov said. “In the next phase of this research, we will determine how we improve that pairing so that each pair of chromosomes separate correctly.”

Laboratories around the world are involved in a different IVG technique that involves a time-consuming process to reprogram skin cells to become iPSCs and then differentiate them to become eggs or sperm.

We skip that whole step of cellular reprogramming. The advantage of our technique is that it avoids the long culture time it takes to reprogram the cell. “Over several months, many deleterious genetic and epigenetic changes can occur.”

Paula Amato, Professor of Obstetrics and Gynecology, School of Medicine, Oregon Health and Science University

Although researchers are also studying the technique in human eggs and early embryos, Amato said it will be years before the technique is ready for clinical use.

“This gives us a lot of information,” he said. “But there is still a lot of work to be done to understand how these chromosomes pair and faithfully divide to really replicate what happens in nature.”