Growing oocytes in the laboratory: is it possible?

Is it possible to complete the development of an oocyte taken from a woman’s ovarian tissue in the laboratory, up to its mature stage and therefore ready to be fertilized in vitro?

This is the question asked by the British and American researchers, authors of a study that appears to be revolutionary.

Revolutionary above all for those women who wish to preserve their fertility despite chemotherapy.

Currently, women who have to undergo therapy to cure cancer have two options. Either   cryopreserve (by vitrification) the oocytes or take some ovarian tissue and then reimplant it later. This second method is much more experimental than the first, but both do not guarantee 100% reproductive success.

The study published in January 2018 tackles the issue differently, and was led by Evelyn Telfer, a biologist at the University of Edinburgh who has been researching reproductive sciences for 30 years.

The study, published in Molecular Human Reproduction   , describes the method that made it possible to grow and mature human oocytes contained within primordial follicles taken through ovarian biopsies, until oocytes were obtained ready to be fertilized.

It is the first time that human egg cells have been grown in a laboratory, from the earliest stages of ovarian tissue to full maturity.

The technique used in the study

To conduct the study, tissue samples were collected from the ovaries of 10 women (between 25 and 39 years old, with an average age of 30) who underwent elective cesarean section at the end of pregnancy.

Forty-eight eggs in an early stage of development were isolated from follicles present in ovarian tissue fragments. They were grown in a laboratory and nine reached the final stages of development, thus reaching maturity.

This is a very important discovery for understanding how the ovary works and how it affects a woman’s fertility, and opens new doors for understanding how a human egg cell develops.

The researchers expect another 5-10 years of work before being able to apply the method. There is still much work to be done to improve the efficiency of the procedure, i.e. to improve the in-vitro development of human oocytes and much remains to be improved in terms of improving the quality of the cells obtained. In fact, according to the researchers, the cells that had reached maturity showed various anomalies . Understanding where the anomalies come from and then adjusting the technique to obtain good quality eggs will help to understand more about the mechanisms that regulate and lead to oocyte maturation.

Implications of the study

This research opens new hope for future women who wish to preserve their fertility when they have to undergo therapies for the treatment of cancer.

It also opens up hopes of understanding the mechanisms that regulate the production of quality oocytes that we know are less and less as the woman’s age increases .

Furthermore, obtaining mature egg cells in vitro could one day save the woman from taking drugs and hormones to stimulate ovulation.

However, the study was conducted on fresh tissue and not on previously frozen tissue, as is the practice. There is still much work to be done in this sense and the road could be further lengthened before this technique actually becomes operational.