Eggs "in vitro"

How to create an egg

Maxim Rousseau, Polit.roo

The study published by the journal Nature (Hikabe et al., Reconstitution in vitro of the entire cycle of the mouse female germ line) was another breakthrough in the field of stem cell applications. The authors managed not only to make the stem cells of mice turn into eggs, but also to achieve the appearance of offspring from these eggs.

Getting stem cells to differentiate into somatic cells of a certain type is always a difficult task, and it is especially difficult to get germ cells (eggs or spermatozoa) from them. The achievements are still small. In 2003, at the University of Pennsylvania, mouse eggs were obtained from stem cells, but developing embryos could not be obtained from these eggs. In 2012, researchers from Kyoto University led by Mitinori Saitou and Katsushiko Hayashi also obtained eggs from mouse embryonic stem cells and achieved the birth of healthy mice from them. Finally, in 2014, scientists from the University of Cambridge and the Israeli Weizmann Institute managed to obtain human germ cell progenitors from skin cells by regulating the work of certain genes, but for ethical and legal reasons did not continue the experiment.

The current study was carried out by the aforementioned Katsushiko Hayashi and Mitinori Saitou and their colleagues from Kyoto University, Kyushu University, Tokyo Agricultural University and the Institute of Animal Husbandry and Crop Production in Tsukuba. Both mouse embryonic stem cells and induced pluripotent stem cells (iPS cells) were used.

Scientists have achieved that the development of these cells led to the appearance of immature egg precursor cells. They then placed the resulting cells in groups of cells taken from the ovaries of mice. They grew them in the laboratory for a month. As a result, according to scientists, they managed to get more than fifty mature eggs in each of these artificial ovaries. They turned out to have much more chromosomal abnormalities than in those eggs that develop in the ovaries of mice in the usual way. But 75% of the cells had the correct number of chromosomes. Some of these cells were artificially fertilized with mouse spermatozoa. It turned out more than 300 embryos, which at the stage of two cells were implanted into the uterus of female mice. However, only eleven of these embryos (i.e. 3%) successfully survived the entire pregnancy. Usually, with in vitro fertilization followed by embryo implantation, the proportion of safely born cubs in laboratory mice is higher, it is 62%. According to Katsushiko Hayashi, researchers have yet to figure out the reasons for this.

Eleven born mice turned out to be healthy and, becoming adults, were able to produce offspring. George Daley of Harvard Medical School, commenting on the results of this work, called it "a stunning achievement."

Mice born from eggs created in the laboratory

If the technique of obtaining eggs from induced pluripotent stem cells is developed and will someday be applied to humans, it will lead to the creation of new methods of infertility treatment, as well as give birth to children to women whose eggs were damaged during chemotherapy. Katsushika Hayashi, however, says that the real clinical application of the new technique is still very far away. "We cannot exclude the risk of having a child with a serious illness," explains the scientist.

Having tried to look into the future, we can say that the artificial production of eggs from iPS cells (in fact, from skin cells) will raise many ethical questions. Potentially, during this process, it is possible to influence the genome of the cell, resulting in a child with the specified genetic characteristics.

A number of researchers warn that attempts to recreate such a complex process as egg development will be influenced by numerous factors that have not yet been studied. "Cells undergo so many laboratory manipulations, each of which can cause deviations, so it will be difficult to figure out which factors play a decisive role," says Alan Spradling, who studies egg development at the Carnegie Institution in Baltimore. In this case, eggs with serious abnormalities can in some cases develop and lead to the birth of offspring. By studying the process of egg development in the laboratory, it is possible to identify its differences from normal, but it is much more difficult, according to Spreading, to establish the details of normal development in the body that are still unknown to us.

Portal "Eternal youth" http://vechnayamolodost.ru  19.10.2016