Scientists Produce Healthy Mice Using Exclusively Male Cells

(Credit: Sangharsh Lohakare/Unsplash) Same-sex reproduction has historically required donor cells, as is the case with egg implantation and some instances of in-vitro fertilization (IVF). Thanks to genetic engineering, however, this might not always be the case. Scientists in Japan have successfully created eggs using male cells, resulting in the birth of several mice that were produced without mothers.

Renowned Kyushu University stem cell researcher Katshuhiko Hayashi presented his team’s achievement this week at the Third International Summit on Human Genome Editing in London. Hayashi had led his colleagues through “reprogramming” a male mouse’s skin cells into induced pluripotent stem (iPS) cells, or former non-reproductive cells that can be engineered into various cell forms. Because male cells contain the XY chromosome combination, Hayashi had to remove the Y chromosome and replace it with an X chromosome from another cell. (Hayashi’s team attempted to devise a way to duplicate the first cell’s X chromosome but was unsuccessful, resulting in the need to pull from a donor.)

(Credit: Rama/Wikimedia Commons)

Hayashi implanted the makeshift eggs inside a mouse ovary organoid, a ball of tissues that function similarly to a natural ovary. After fertilizing the eggs with sperm, his team implanted the resulting 600 embryos into surrogate mice. Seven of these embryos became mouse pups, which grew into adults with normal lifespans and successful mating routines.

This research, which Hayashi has since submitted to scientific journals, is just the beginning. His team is now working to replicate their achievement using human cells, which they hope to turn into lab-created eggs. Scientists have made similar attempts before, but their cells have failed to advance past the meiosis stage, which is necessary for the development of eggs and sperm.

Should Hayashi and his colleagues successfully produce eggs in the lab, it could pave the way for novel infertility treatments and for same-sex procreation that incorporates both partners’ genes. Male couples who wish to produce children currently have to choose whose sperm will fertilize a donor egg, which is implanted in a surrogate mother for gestation. Developments like this one, however, could allow couples to use one person’s sperm to fertilize an egg made from the other person’s cells, or even allow a single person to produce a child using only their genes. Hayashi says this could be possible within a decade—but other scientists think that’s a bit optimistic.

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