11 October 2016

New eggs

Maxim Russo, Political scientist.<url>, based on The Guardian: Evidence suggests women's ovaries can grow new eggs

An unexpected message was made by a group of scientists from the University of Edinburgh. If it is confirmed, it will overturn the established ideas about the development of germ cells in the human body. Researchers claim to have discovered the ability of adult women's ovaries to produce new eggs. This effect occurs when certain drugs are used, which are usually used to treat lymphoma.

According to modern concepts, all eggs are formed in the body of a woman even in the embryonic period of development. Their precursors are the primary germ cells (gonocytes). They develop in the yolk sac, an embryonic organ that works in humans until the end of the first trimester of pregnancy, and then is reduced. During embryo development, gonocytes leave the yolk sac and travel through the entire embryo to where the sex glands begin to form. Gonocytes that enter the ovaries give rise to oocytes – future eggs, and those that enter the testes – spermatozoa. In the ovaries of the embryo, oocytes divide intensively, and after birth, cell division no longer occurs, the oocytes only grow and mature. Thus, in the body of a born woman, there is a very large (hundreds of thousands), but still a limited number of future eggs.

Therefore, Professor Evelyn Telfer and her staff were very surprised by the results of their research. They studied the development of eggs in the body of women with cancer during chemotherapy. The researchers set out to find out why the ABVD drug complex used in the treatment of Hodgkin's lymphomas, unlike many similar drugs, does not cause fertility problems in patients.

To answer this question, they took ovarian biopsies from women undergoing such treatment. The study involved eight patients who received ABVD drugs, three women whose course of treatment was based on a different scheme (OEPA-COPDAC), as well as ten healthy women. When studying the drugs, it turned out that the number of oocytes in them is significantly (from two to four times) more than in healthy women of the same age. Evelyn Telfer tells The Guardian: "It was something wonderful and completely unexpected for us. New eggs appear to be forming in the tissues. It was considered a dogma that there is a fixed number of eggs in human ovaries and no new ones can be formed throughout life."

Preparation of ovarian tissue of a woman who underwent chemotherapy under the ABVD scheme,
(top left) contains more follicles,
in each of which there is an oocyte,
than other women's fabrics.

If the discovery is confirmed, it will give doctors a new method of treating female infertility. But Evelyn Telfer believes that it is too early to talk about its use in infertility treatment clinics. According to her, the functioning of the ovaries has not been studied enough, so first fundamental science should understand the effect of the drug and only then it will become clear whether it can be used in clinical practice.

The message about the effect discovered by Edinburgh scientists was met by other experts with delight, to which a fair amount of skepticism was mixed. "I think that these data, as well as the identification of the mechanisms involved, can pave the way for the development of new methods of infertility treatment or prolong the duration of the reproductive period of women by replenishing the ovaries with new follicles," says Kenny Wallberg, senior consultant at Karolinska University Hospital in Stockholm. "This suggests that the ovary is indeed a more complex and versatile organ than we were taught, and it has the ability to renew itself." Others, including David Albertini, director of the laboratory of the Center for Human Reproduction in New York, are less convinced of the reality of the appearance of new eggs. "To be honest, I think there are too many other ways to explain the results, and the production of new oocytes is just one of them."

Albertini says that oocytes could already be contained in the ovaries and appear on the surface due to the reaction of the tissue to the drug. Also, the effect of the drug could lead to damage to the follicles and splitting them in half. In this case, the oocytes contained in the follicles did not multiply. According to Albertini, it is necessary, firstly, to make sure that the Edinburgh results are reproducible, and, secondly, to find an explanation for them.

Telfer and her colleagues claim that the formation of new oocytes seems to them the most likely explanation, since the cells found in the tissues of patients undergoing ABVD therapy look younger than normal oocytes. They are more like oocytes that have not yet reached maturity in the ovaries of girls.

Earlier, Evelyn Telfer's group discovered stem cells in the ovaries, which theoretically can serve as a source of new oocytes. But even this discovery is doubtful among a number of colleagues. At the moment, the only thing that Telfer and skeptics agree on is the conviction that it is too early to talk about using such a method to treat infertility.

The results of the Edinburgh scientists' research were presented for the first time in July at the annual conference The European Society of Human Reproduction and Embryology (ABVD chemotherapy for lymphoma affects number and morphology of primordial follicles in the adolescent and adult ovary), and are currently being reviewed before publication in a scientific journal.

Portal "Eternal youth" http://vechnayamolodost.ru  11.10.2016

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