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Swiss scientists obtain sterile mice to produce rat sperm



In Greek MythologyChimera‘ is a fabulous monster usually depicted with the head of a lion, the body of a goat and the tail of a dragon. In the scientific world, the word indicates a body generated artificially of cells that have different genetic characteristics or that come from two or more species.

Through the generation of chimeras, for example, Recently Some research groups managed to form organs of rats in mice. For that, they used pluripotent stem cells and embryos genetically modified so that they could not give rise to specific organs.

Generating eggs or sperm from pluripotent stem cells remains a very challenging task.

Now, researchers from the Federal Polytechnic School (ETHZ) and the University of Zurich (UZH), both in Switzerland, generated sperm mouse inside mice that are sterile due to a genetic mutation. The work is published today in the journal Stem cell reports.

Pluripotent stem cells or PSCs – which have the ability to give rise to all cell types that exist in the body provide a powerful tool for biomedical research, but generating eggs or sperm from them remains a very difficult task. challenger. The Swiss investigation, while preliminary, represents a step forward in this achievement.

“Our work offers proof of principle that it is possible to exclusively generate sperm of one species in sterile animals of another”, he tells SINC Ori Bar-Nur, a stem cell biologist at ETHZ and lead author of the study. “The importance of research lies in the understanding that such scientific feat can be achieved. But in addition to a conceptual breakthrough, this method could have important future applications,” he adds.

Immobile sperm and low fertilization rates

To accomplish this, the researchers injected mouse PSCs into mouse embryos in which they were mutant a gene essential for sperm production. The mouse stem cells were cultured together with the mouse cells, thus generating a chimeric animal composed of genotypes of the two species.

As a consequence of the sterility-inducing genetic mutation, an empty niche developed within the testes, allowing mouse cells to colonize them and generate sperm.

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Despite its sterility, the host could support the efficient production of sperm from a different animal species.

Ori Bar-Nur, ETHZ

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“We were surprised at the relative simplicity with which we were able to mix the two species together to produce chimeras. viable. These animals were generally healthy and developing normally,” says Bar-Nur.

“The second surprise was that, in fact, all the sperm in the chimeras were from mice. This means that despite its sterility, the host could sustain the efficient production of these cells and a different animal species.”

That yes, although the sperm morphologically seemed indistinguishable from those produced by normal mice, they were immobile and the fertilization rates of eggs were especially low. In the future, the authors will try to produce live animals from mouse sperm that was produced in chimeras.

Possible future applications

The authors note that the study could pave the way for two important applications. The first involves improving the production of transgenic mice to model human diseases in biomedical research.

A long-term goal is to produce gametes from endangered animals within individuals of other species.

A long-term goal is to produce gametes (eggs and sperm) of animals that are in danger of extinction within specimens of other species, to support the means of conservation of biodiversity.

“Thanks to this procedure, we were able to produce the germ cells of a rodent in endangered through the generation of chimeras”, says Bar-Nur. “At the current pace of stem cell technology, I think it will be possible to achieve this goal within a few years.”

“However, for animals that are not rodents, it will be necessary to more time and further scientific and technological development. Furthermore, we have yet to achieve the production of female reproductive cells (the eggs) in sterile female mice”, he concludes.



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