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Researchers made sperm-like cells and used them to create new mice

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Researchers say they've been able to make immature mouse sperm in the lab and use it to generate offspring. The study, led from Nanjing Medical University, may be a milestone in the path to developing treatments for infertility. Researchers have tried for years to create sperm in the lab, but it wasn't until now that a group appears to have started with stem cells and clearly led them through meiosis, a process in which a cell divides into new ones with fewer chromosomes — sperm. In this case, the researchers did not fully generate sperm, but by exposing the pre-sperm cells to testicular cells and key hormones, they were able to produce what resembled an immature sperm. By using those to fertilize egg cells from other mice, the research team was able to prove their viability. The findings are being published today in Cell Stem Cell.

"The next exciting step would be to accomplish the same feat with human cells."

"This paper reports a significant advance in understanding sperm development and production," Peter Donovan, a biology professor and molecular genetics researcher at UC Irvine, who was not involved in the study, tells the Genetic Expert News Service. "Of course the next exciting step would be to accomplish the same feat with human cells." The hope is that by reverting cells from an adult into a embryonic stem cell-like state, researchers could then lead those cells through a similar process, allowing for the generation of sperm from people who are otherwise unable to produce it. Donovan, along with other researchers who spoke with the Genetic Expert News Service, warn that there are likely to be ethical issues as this line of research proceeds. One question, Donovan poses, "How can we tell if spermatids made in a laboratory are really of the same high quality as those made and tested by natural selection in the testis?"

And while Nanjing Medical University's results are impressive, Nature points out that there have been advances in this area before that scientists have had trouble replicating. One researcher, who has produced early versions of sperm-like cells in the lab, told Nature to be "very cautious about the implications" of this study. Another researcher said they wouldn't believe the results until reproduced in their own lab. For their part, the research team behind the study remains confident, telling Nature that while variations in findings are to be expected, the protocol they're describing today should be repeatable.