Health. – A surprisingly simple method could provide a new tool for reproductive medicine

MADRID, 17 (EUROPA PRESS)

Researchers in Japan have found that activating just eight genes to produce proteins that control genes is enough to convert mouse stem cells directly into oocyte-like cells that mature and can even be fertilized as eggs. in the journal Nature. . This surprisingly simple method could provide a new tool to produce specialized cytoplasm for reproductive medicine.

In addition to providing new perspectives on the mechanisms of egg development, research can lead to a simple way to generate highly specialized substances, unique to oocytes, for use in reproductive medicine and biology.

Stored in the body until they mature into eggs ready for fertilization, oocytes are the first step in creating a new human life.

Oocytes are extremely unique due to their ability to produce more than two hundred highly differentiated cell types needed to create an individual person, and a key to this ability is the complex mixture of substances in the fluid cytoplasm that fills cells. researchers.

Oocytes and their cytoplasm are so extraordinary that replacing the nucleus that contains the DNA of a cell oocyte with a cell in the body, a process called somatic cell nuclear transfer, can produce new life, as demonstrated by the famous Dolly the sheep .

Therefore, a fundamental understanding of oocytes and their development is important both to advance reproductive medicine and to better understand how life propagates, but knowledge of many genes that orchestrate oocyte development is still far from complete.

Analyzing the development of mouse oocytes, researchers led by Katsuhiko Hayashi, a professor at Kyushu University School of Medical Sciences, have now identified eight genes for gene-triggering proteins, known as transcription factors, that are not only necessary for oocyte growth. but it can also directly convert mouse stem cells into oocyte-like cells.

“I was initially completely distrustful that the mouse stem cells took the shape of oocytes so quickly and easily based on the introduction of only a handful of factors, but repeated experiments showed that this is true,” says Nobuhiko Hamazaki, the study’s lead author to results and assistant professor at Kyushu University at the time of the research – The discovery that eight transcription factors could lead to such large changes was quite surprising.

Working with researchers at RIKEN, Hayashi’s group found that both mouse embryonic stem cells and induced pluripotent stem cells (iPS), which can be created from adult body cells, are constantly transformed into similar cells. oocytes. when they are obliged to produce the whole. out of eight transcription factors, only four factors being sufficient in some cases, although with lower reproducibility.

“It’s remarkable that stem cells can be transformed directly into oocyte-like cells without following the same sequence of naturally occurring steps,” says Hayashi.

When cultured in the presence of other cells that are generally found around oocytes, oocyte-like cells have developed structures similar to mature ova, but with an abnormal chromosomal structure. Despite this, oocyte-like mature cells could be fertilized in vitro and show early development, some even progressing to an eight-cell stage.

Although modified oocyte-like cell nuclei may not be usable in the long term, this is not a problem for applications that primarily require oocyte cytoplasm, such as reproductive biology studies and treatments such as replacement therapy. . mitochondria, in which parts of the oocytes are replaced to prevent mothers from transmitting mitochondrial diseases to their children.

“Oocyte cytoplasm is an invaluable resource in reproductive medicine and biology, and this method could provide a new tool to produce large quantities without any invasive procedure,” says Hayashi. “Although the processes may be even more complex for humans, these initial results in mice are very promising.”