May 19, 2024

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Osaka University: Mammals don’t need female eggs to reproduce

Osaka University: Mammals don’t need female eggs to reproduce


Osaka University: Mammals don’t need female eggs to reproduce.


On March 8, 2023, Professor Katsuhiko Hayashi of Osaka University in Japan announced at the 3rd International Summit on Human Genome Editing that they had grown eggs using cells from male mice, and these eggs could be fertilized with male sperm. When implanted into female mice, they developed healthy, fertile offspring [1] .


While this research is still a long way from being applicable to humans, it provides an early proof-of-concept that opens up new possibilities for treating some causes of infertility and even allows for the creation of single-parent embryos, which could It is a major progress with great potential application value.


Osaka University: Mammals don't need female eggs to reproduce.Professor Katsuhiko Hayashi (source:



For mammals, only sexual reproduction can be carried out, requiring the union of male sperm and female eggs to produce offspring, which have genetic material from both parents.

However, some genes are expressed only from the paternal allele and others from the mother’s allele, so-called genomic imprinting, which is achieved through epigenetic methylation, genomic imprinting The existence of hinders the realization of parthenogenesis or parthenogenesis.


Scientists have long struggled to achieve the feat of parthenogenesis, or parthenogenesis, in mammals.


In July 2021, Katsuhiko Hayashi and others published a research paper entitled: Generation of ovarian follicles from mouse pluripotent stem cells in the journal Science [4] .

The research team induced the gradual differentiation of embryonic stem cells in female mice, and finally produced a large number of embryonic ovarian somatic cell-like cells (FOSLCs) similar to ovarian somatic cells .

When these FOSLCs were co-cultured with oocytes derived from mouse embryonic stem cells, the FOSLCs produced ovarian follicle structures in which mouse embryonic stem cell oocytes developed into viable eggs.

These in vitro-generated eggs could be fertilized, and the fertilized eggs were transplanted into the wombs of female mice, which produced healthy offspring.


Osaka University: Mammals don't need female eggs to reproduce.



With the above-mentioned research foundation, Katsuhiko Hayashi and others started the project of using the cells of adult male mice to make eggs.

They reprogrammed these cells to create induced pluripotent stem cells (iPSCs) . They grew the cells in the lab until some of them spontaneously lost their Y chromosome.


The research team then treated the cells with Reversine , a compound that promotes chromosome misdistribution during cell division. They found cells in which two X chromosomes appeared.


On this basis, the research team provided iPSCs with the genetic signals needed to form immature eggs. They then used the mouse’s sperm for fertilization and implanted the resulting embryos into the uterus of female mice.


The survival rate of these embryos was low, with only 7 of 630 embryos transferred developing into pups (1.11%) , but these pups grew normally and became fertile adults, the research team said.


Katsuhiko Hayashi , who led the study , said the technology is still a long way from medical applications because there are many differences between mice and humans that often translate discoveries in reproductive and stem cell biology from mice Complicating clinical efforts.

Currently, the research team is carefully characterizing the experimental mouse pups to look for how they differ from normally born pups.


Regarding the results of this research, Mitinori Saitou , a developmental biologist at Kyoto University in Japan , said that performing the same technique on human cells may require a longer period of culturing egg cells in the laboratory, and the culture period becomes longer, so genetic mutations and expression Epigenetic abnormalities are cumulative. Therefore, the shorter the incubation time, the better.


In addition, epigenetic marks on the genome can affect the development of offspring more than embryonic stage, so this study needs to further explore the epigenetic modification and long-term effects of these male mouse cell-derived eggs.

More importantly, the survival rate of embryos constructed by this technology is still too low, and the success rate needs to be further improved.

If these hurdles are overcome, the chromosome engineering approach developed by Lin et al. has the potential to provide a cure for some infertility caused by sex chromosome abnormalities, such as Turner syndrome (in which patients lack an X chromosome or part of it) .

The findings may also take human reproduction into new territory.

If applied to humans, it may help male spouses have biological children, and in the future, it may also help single men have biological children.



In the end, Katsuhiko Hayashi said that this technology not only requires technical improvements to biological methods, but also requires further discussion of ethical implications, and he does not know whether this technology can really adapt to human society.








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Osaka University: Mammals don’t need female eggs to reproduce.

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