A new assisted reproduction technique achieves pregnancy in an infertile woman due to the poor quality of her oocytes

Researchers from the Spanish Embryotools center and the Institute of Life of Athens assisted reproduction center have achieved scientific milestone that will mark the future of assisted reproduction: in the framework of a pilot clinical trial with women they have achieved the first recorded pregnancy in the world in which the technique of Maternal Spindle Transfer has been applied (MST, Maternal Spindle Transfer, in English) to solve infertility problems.

The Greek woman is 27 weeks pregnant.

What is the Maternal Spindle Transfer?

It is one of the therapies that help prevent diseases that affect mitochondria, the cellular organelles that are found in the cytoplasm of the cell and that supply it with energy.

The technique consists in extracting the meiotic spindle (nucleus) of an unfertilized oocyte from a patient carrying mutations in the mitochondrial DNA, and introducing it into the ovule of a donor with healthy mitochondria, from which its original nucleus has previously been extracted. Finally, the resulting oocyte is fertilized with the couple's sperm.

The technique, legally approved since 2015 only in the United Kingdom, It is known as 'embryo of the three fathers'. The world's first baby conceived with this technique was born in Mexico in 2016 thanks to a team from a clinic in the United States.

MST was then used to prevent the transmission of mitochondrial diseases, not to solve infertility problems.

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Useful with poor quality oocytes

Embryotools, based in the Parc Científic de Barcelona (PCB), has been testing this technique in mice for years and thus its researchers discovered that the MST technique could also be used successfully to solve infertility problems caused by poor oocyte quality.

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In 2016, they obtained permission from the Greek authorities to start the pilot clinical trial. Now, they already have results: the first Greek woman treated with this technique is 27 weeks pregnant.

This is a 32-year-old woman with a low ovarian response, who had already undergone two operations for endometriosis and four cycles of in vitro fertilization without achieving gestation.

The study will include a total of 24 other women with similar infertility problems. With the 'reconstructed' oocytes using MST, the researchers have already managed to obtain eight embryos from as many partners, although they have not yet been transferred to the patients waiting to control in detail the evolution of the first pregnancy achieved.

Preserve genetic inheritance

Dr. Nuno Costa-Borges, scientific director and co-founder of Embryotools, emphasizes one of the advantages of this technique, compared to other assisted reproduction, such as conventional egg donation:

More than 99% of the conceived baby's DNA would come from his biological mother and father, despite resorting to an egg from a donor:

“Although gametes from one man and two different women (the patient and the donor) are needed, the nuclear or genomic DNA, responsible for the vast majority of the phenotypic characteristics of the future baby, would come from the biological mother and father, as in a normal fertilization process. The donor would provide only mitochondrial DNA, which encodes only 37 genes and represents less than one percent of human DNA. ”

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In addition, the researcher adds, "This mitochondrial DNA provided by the donor would not be transmitted to subsequent generations if the resulting baby were a male, because the mitochondrial DNA is only transmitted through the mother."

A long road ahead

Dr. Gloria Calderón, co-founder and director of Embryotools. It highlights the safety that this technique has shown in all the tests carried out to date, although it also indicates that it is necessary to be cautious because

“The transfer of maternal spindle is an experimental technique in the validation period. It cannot be incorporated into the routine of any assisted reproduction clinic overnight. It requires special technology and extensive training of researchers with a long learning curve. ”

Embryotools researchers are open to being able to carry out a trial of these characteristics in Spain, but the project is not immediately feasible.

Law 14/2006, of May 26, on assisted human reproduction techniques does not specifically prohibit this technique, but it establishes in an annex the authorized practices and also provides a special permit for other techniques not contemplated. The transfer of maternal spindle is not yet contemplated in the regulations.

Thus, the first step should be to obtain the endorsement of the National Commission of Assisted Human Reproduction.

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