By modifying the activation of eight genes for transcription factors, Japanese researchers were able to obtain fertilizable oocytes from stem cells.
In Vitro Fertilization
This could be the beginning of a revolution in assisted fertilization. Japanese researchers at Kyushu University School of Medical Sciences have succeeded in deriving mice eggs from stem cells by altering the activation of just eight genes. If confirmed in humans, this technique could provide an alternative to donors for assisted reproduction. The results of this discovery were presented on Dec. 16 in the journal Nature.
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In vitro fertilization
The researchers were surprised that converting stem cells into oocytes could be done so easily. “I was completely incredulous at first when I saw that mouse stem cells took the form of oocytes so quickly and easily by introducing just a handful of factors,” said Nobuhiko Hamazaki, the study’s first author. The oocyte is a female reproductive egg, the female equivalent of sperm. It is found in follicles located in the ovaries, which are blocked until puberty before maturing into a primary follicle in the middle of each cycle until ovulation.
Forced activation of certain genes has succeeded in turning mice pluripotent stem cells, the cells that can become any cell type in the body, into fertilizable eggs. The mature cells were able to be fertilized in vitro and “showed early development, some even reaching the eight-cell stage,” the researcher added. “When cultured in the presence of other cells normally found around oocytes, the oocyte-like cells develop structures similar to those of mature oocytes but with an abnormal chromosome structure.” They do not undergo meiosis to separate the entire chromosome into two, as they should, and are not functional. Nevertheless, they have been fertilized.
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Cytoplasm an invaluable resource for reproductive biology
“It is remarkable that stem cells can be converted directly into egg-like cells without following the same sequence of steps that occurs in nature,” says Prof. Katsuhiko Hayashi. The cytoplasm of the Oocyte is a unique and very valuable thick solution located in the cell around the nucleus that is used in assisted reproduction techniques. Oocyte cytoplasm contains proteins and maternal RNA that are fundamental to the formation of life.
“Oocyte cytoplasm is an invaluable resource for reproductive biology and medicine, and this method could be a new tool to produce large amounts of it without invasive procedures,” concludes Professor Katsuhiko Hayashi. In humans, the processes could be even more complex, but these initial results in mice are very promising.
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References
Reconstitution of the oocyte transcriptional network with transcription factors
