Egg doublers

There is a replacement for eggs Pyotr Smirnov, "Newspaper.
Ru»

Contrary to the school textbook, new eggs can appear in the female ovaries after birth. Scientists have found stem cells capable of turning into oocytes and populating ovaries that have used up the entire innate supply. Quite healthy mice are born from them.

If it were not for the external genitalia, then only parents would probably be able to distinguish a boy from a girl in the first years of life. Only a change in the hormonal background determines the physique, promotes breast growth and the formation of the sex glands. And it is hormones that, upon reaching puberty, prepare the body for the main task of life – the dissemination of its genetic information. And despite the fact that most of the cells carrying this very information never reach their goal, both male and female bodies constantly keep themselves in shape.

The only difference is that in men, the formation of spermatozoa goes on continuously, while the formation of eggs in the ovary is completed in mammals at the stage of embryonic development. During the menstrual cycle, only the maturation of the eggs and the preparation of the entire reproductive system for potential conception takes place. That is, if the age of spermatozoa is determined only by the time they stay in the pathways, then the egg is the same age as the woman. It is for this reason that older women are more likely to have children with chromosomal rearrangements and congenital anomalies.

Ji Wu from Shanghai Jiaotong University managed to find cells in adult ovaries that can produce gametes and even get healthy young from these eggs. So far, we are talking only about mice, but this work can be a turning point both in the treatment of female infertility and in preventing the birth of children with mutations.

Every glass of alcohol drunk, a cigarette smoked, stress, carcinogens and medications, as well as any other environmental factors, inevitably affect the state of the ovaries and practically formed eggs "sleeping" in them. Spermatozoa, formed by billions in the testicles from dividing progenitor cells throughout life, undergo strict selection every time, which is why, with the next fertilization, the probability of a genetic error on the male side should theoretically be less (however, this has not been proven experimentally).

As a last resort, men who are afraid for their genetic material have the opportunity to freeze several batches of sperm. But in women, this option has appeared only recently, and even then its final effectiveness still leaves much to be desired: in the freezing / defrosting cycle, cells are inevitably damaged. Of the billions of spermatozoa that have only a tightly packed nucleus and a flagellum with mitochondria, there will always be a survivor and a viable one. A completely different approach is required for large eggs, which contain all the necessary components for independent life and development during the first few days. And even in the case of additional hormonal stimulation, as, for example, it is done with in vitro fertilization, only a dozen can be obtained.

It is not surprising that the "special offer for a businesswoman" to freeze several of her eggs has not yet been included in the list of cryobanks services. Moreover, after the publication in Nature Cell Biology, the accents may change significantly.

Ji Wu started his project based on isolated reports of the detection of active, dividing cells in the ovaries of adult mice. After several attempts, the scientist and his colleagues really managed to isolate diploid stem cells from the ovary, that is, containing a double set of chromosomes.

The most logical and obvious confirmation of the ability of these cells to form gametes would be a demonstration right under the microscope of meiosis – division in two without chromosome doubling.

Due to the lack of an appropriate microenvironment and a wide range of stimulating molecules, it has not yet been possible to do this, but Chinese scientists have demonstrated the biochemical similarity of these cells, called FGSC (female germline stem cells), with gametes and gamete progenitor cells.

The "stemness" was confirmed by numerous equivalent divisions, which Wu and co-authors have been observing for 15 months, replanting these cells. The scientists separately noted that, by the nature of growth and structural features, their FGSC wards are fundamentally different from embryonic stem cells obtained from a zygote formed by the fusion of male and female gametes.

The main achievement of Wu is that he was able to demonstrate the ability of FGSC to repopulate emptied ovaries and even restore fertility to mice.

After a course of cytostatics cyclophosphamide and buslfan, which "cleaned" the ovaries of mice from eggs, scientists transplanted FGSCS previously isolated from these ovaries (FGSCS, and not the eggs themselves, which are not capable of division and differ in a "half-set" of chromosomes). What was missing on the microscope slide was enough in the ovaries, and after two months they were again completely populated.

Moreover, 80% of these females became fertile again, and the offspring born after their natural fertilization did not differ from their counterparts and had no genetic disorders.

Now scientists are trying to understand where these FGSCS in the ovary come from, whether they take part in in vivo oogenesis (formation of new eggs) in healthy ovaries, and if so, what is the numerical ratio between "innate" and newly formed eggs.

The main question is whether these results can be extrapolated to humans. The authors themselves have so far refrained from commenting, but if they manage to demonstrate that FGSCS repopulate the ovaries from blood, then the return of the ability to procreate to women can become quite real. As for those who will take care of this issue in advance, the horizons are much wider.

Firstly, stem cells tolerate freezing /defrosting much better than specialized gametes, so if you learn how to isolate them, then the storage issue will be solved much easier. And secondly, if we can find a way to stimulate FGSC division in the adult ovary, this will significantly reduce the likelihood of genetic rearrangements – after all, the formation of new oocytes will occur immediately before conception. Finally, women whose ovaries have been artificially cleared of eggs – for example, during a course of chemotherapy in the oncology department - will surely say thank you for such a discovery.

Portal "Eternal youth" www.vechnayamolodost.ru 13.04.2009