Here’s your dose of weird science for the day: A team of scientists from Zurich turned sterile mice into rat sperm factories using stem cell injections. They hope the research, published Thursday in Stem cell reportswill open the door to new fertility treatments, especially for animals at risk of extinction.
“In the future, if there is a critically endangered mouse species and we just have a skin biopsy and it goes extinct, maybe we can produce stem cells and maybe generate germ cells from critically endangered animals,” Ori Bar-Nur, a biologist at ETH Zürich in Switzerland and co-author of the new study, told The Daily Beast.
Bar-Nur and his team used a technique that allowed them to inject stem cells derived from mouse embryos or their skin, at a very early stage of a mouse embryo. The organism then developed into a mouse-rat chimera, meaning it contained cells from both mice and rats.
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Importantly, though, all of its sperm-producing cells came from the mouse, so the chimera produced exclusively mouse sperm.
Previous research had successfully led to the opposite result – mouse chimeras that produced mouse sperm. Joel Zvick, a biologist at ETH Zürich who led the new study, told The Daily Beast that both research projects complement each other, even if their methodologies differ.
Still, the researchers were unsuccessful in using chimeric mouse sperm to fertilize mouse eggs and produce viable mouse babies. According to the study, sperm from rat-mouse chimeras was inferior to naturally produced rat sperm.
Bar-Nur said this method seems to work best in species that are closely related by evolution. Furthermore, the two species in the chimera must have similar gestational times for fertilization to work.
Fluorescent staining of mouse sperm.
Courtesy of the authors
The researchers are now trying to go a step further and grow live mice with mouse-mouse chimera sperm. They are also looking to adapt their methods for producing eggs, which, according to Bar-Nur, must operate on the same principles as sperm. But we won’t be able to do IVF or other fertility treatments on human mouse chimeras anytime soon – and maybe it’s for the best.
“If you get a heart or a pancreas, which grew through a chimera, it’s just an organ,” Zvick said. “But if you generate sperm and eggs, of course for a lot of people, that would be much harder to accept.”
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Other studies have also used this stem cell-based method to grow a mouse pancreas inside a mouse — but more research on the technology and ethics is needed before scientists can grow human organs in animals for use as a transplant.
“This can raise a lot of questions, and that’s not the purpose of our research,” said Bar-Nur. “We would like to try to save very cute endangered mice and rats, not generate human germ cells inside animals.”
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