Men are more expendable than women

Success in conception with sperm from the test tube : Are men expendable?

For the first time, Chinese researchers have grown sperm from mouse embryonic stem cells and produced healthy mice. If it is possible to repeat the procedure with human stem cells, it could not only help men whose testicles do not have fertile sperm to mature. Under certain circumstances, women could use it to produce their own sperm and father genetically related daughters without male involvement.

Recipe for retort semen

For several years now, researchers have been trying to grow egg and sperm cells from embryonic stem cells. Theoretically, this should be possible because the all-rounder cells form almost every human tissue. However, it turned out to be particularly difficult to simulate the conditions in the Petri dish that cause the germ cells in the testes and ovaries to mature from progenitor cells. In particular, imitating the complex halving of the chromosome set, meiosis, did not succeed. The research team led by Jiahao Sha from the Medical University of Nanjing now seems to have overcome this hurdle, at least with mice.

With the help of a molecule cocktail, the researchers first transformed the embryonic stem cells into precursor cells for sperm. In a second step, they bathed these primordial germ cells in testosterone and also embedded them in the testicular tissue of mice. With the sperm sprouting from it, Sha's team was then able to fertilize egg cells and even produce healthy mice, the researchers write in the journal "Cell Stem Cell".

The genetic makeup of the artificial sperm is apparently normal

“What matters is whether this technique is reliable enough to produce genetically normal offspring,” says Terry Hassold, molecular biologist at Washington State University. The Chinese colleagues carried out a series of tests to prove this. However, further investigations are needed to determine whether the meiosis is normal and whether the sperm have the correct number of chromosomes. However, if other laboratories confirm that the technology works, it could fundamentally change the treatment of infertility. "Fertilization clinics will pounce on it."

However, it will be a long time before the procedure with human stem cells can be repeated and brought close to being used, says Berlin reproductive medicine specialist Heribert Kentenich. "It must be ensured that the activity pattern of the sperm genes is not changed by the procedure and that the next generation of mice is also healthy before it can be used in humans."

The use of artificial sperm cells would be legal in Germany

In addition, the process still needs to be further developed. Because for the treatment of male infertility, it makes no sense to choose any embryonic stem cell line as a starting point for sperm breeding: the embryonic cells would be genetically just as different as the sperm from any sperm donor. This is why the Chinese researchers are already working on repeating the procedure with a special type of stem cells, ips cells, which can be made from a patient's skin or other tissue samples. Sperm grown from such ips cells would be indistinguishable from the patient's natural sperm cells.

Whether the artificial sperm came from ips or embryonic stem cell cultures - both would be permissible under the German Embryo Protection Act, says Jochen Taupitz, lawyer and member of the ethics council. It is forbidden to produce human embryos for research purposes only. However, if the goal is to bring about a pregnancy, the procedure would be permitted.

Genetic changes would also be feasible

According to the current law, it would even be possible to genetically modify the stem cells, for example to eradicate a hereditary disease, before they are then converted into sperm or egg cells. "It is true that the Embryo Protection Act makes changing germ cells a criminal offense," says Taupitz. "But if the gene change takes place at a time when the cell was not yet a germ cell, ie as a stem cell, then this is not expressly regulated by law." It is not for nothing that Taupitz and the Ethics Council have been calling for the new possibilities of reproductive medicine for some time to discuss socially and to close the gaps resulting from technological progress in the law, which is now almost three decades old.

In principle, Chinese technology would enable women for the first time in human history to father children without any male accessories. All that would be required was an ips cell culture from the woman's skin cells, from which sperm cells could then be grown, with which she could fertilize her own egg cells. That would also be permissible under German law.

Heribert Kentenich would still not do that. “As reproductive medicine specialists, we often go off the beaten track and treat lesbian couples or single women,” says the head of the Fertility Center Berlin. "But if a woman absolutely wanted to have sperm produced from her own skin cells and refused to donate sperm, I would first psychologically question whether that is an understandable wish." It cannot be ruled out that there might be colleagues who would handle it differently. "Somewhere there is always someone who is up for any nonsense."

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