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Scientists at the University of Edinburgh have developed a technique for preserving eggs from female cancer patients, allowing them to have children later in life, even though treatment may have made them infertile.
Dr Simon Fishel, Managing Director of CARE Fertility Group, said:
“This is an interesting study in the early research phase of understanding the how to grow undeveloped follicles and their immature eggs in vitro. Several years work will need to be undertaken to establish if developing such immature follicles in vitro offer a risk-free option for preserving fertility and a means of obtaining donor eggs. There has been a moratorium in the UK for more than ten years on the use of immature sperm because of the feared risks associated with potential genetic dysfunction during maturation in vitro; similar concerns need to be excluded with the use of very early (primordial) follicle growth in vitro before its introduction into clinical practice.”
Dr Jane Stewart, Newcastle Fertility Centre at Life, said:
“This work increases our understanding of the maturation of human eggs in the lab and takes us a step nearer the goal of storing immature eggs for fertility preservation for women.
“Fertility preservation for women about to undergo potentially sterilising treatments is currently relatively limited in its application. The reason for this is that for ultimate use of eggs they need to have matured to a state where they are capable of being fertilised. Unlike men who produce millions of sperm in a single ejaculate only one or two oocytes reach maturity in a natural menstrual cycle. Mature human eggs are large cells and are difficult to freeze in tact and higher numbers can only be obtained following a course of ovarian stimulation and an egg retrieval procedure. It is often not possible to complete such treatment in the short time available and the hormone treatment may not appropriate in some conditions. Thus it is not a very practical solution in many cases and not commonly undertaken.
“It is relatively simple (although still requiring an operative procedure) to collect a biopsy from a woman’s ovary and this can be done at short notice and without prior hormone treatment. The storage and use of such biopsies (which may contain abundant but immature eggs) remains experimental however. Possible re-implantation of tissue may allow resumption of ovarian activity but this prospect is limited by the effective lifetime of such biopsies and also the risk of re-introducing for example cancer cells to the woman following successful treatment.
“Eggs develop in association with a bundle of cells in the ovary known as a follicle. I the later stages of follicular development this contains a fluid filled area which effectively ruptures, releasing the egg at ovulation. Whilst preliminary maturation of immature eggs within their follicle is possible in the lab, and the final maturation stage of eggs outwith the fluid follicle is also possible there is a gap between these two steps which prevent the full development of a mature and fertilisable egg from an immature egg found in the biopsy tissue. It is the transition between immature follicle and egg to the fluid containing and mature egg/follicle complex which is the sticking point.
“This paper addresses this “gap”. The findings of this team are that they are able to take the immature eggs contained in a bundle of cells known collectively as a primordial follicle to the next step of development. They have been able to continue to grow immature follicles to fluid containing (so-called antral) follicles in the lab and have shown that they appear normal and secrete oestrogen as expected. Whilst this does not close the gap entirely and therefore does not yet represent the final step to ensure the usefulness of ovarian biopsies for fertility preservation; it is a step which will enhance understanding and allow further progress in this process to be made. As the authors have advised it will be some time yet before this progress and subsequent work will reach clinical practice however it is an important step in the right direction and heartening for all those concerned in managing women whose fertility is at risk.”
Professor Robin Lovell-Badge, Head of Division at the MRC National Institute For Medical Research, said:
“The authors have shown that culture methods developed in other mammals can work to allow the growth of human oocytes (eggs) to a size aproaching that which can be fertilized. This was done beginning with small (preantral) follicles, which include other cells that support and help nourish the oocytes in addition to the oocyte itelf, and importantly these follicle cells also multiplied and behaved apparently as they would if still in the ovary. This is an important step towards the goal allowing, e.g. girls undergoing chemotherapy or other treatments for cancer, to have their own children, by freezing pieces of ovary prior to treatment and then at a much later point, thawing these, growing the oocytes and fertilising them in vitro.
“It appears that the cultured follicles can grow much faster than they would normally do in the ovary, which is of scientific interest and practical importance, given that it normally takes many months, something that would be difficult to achieve in the lab. The work suggests that methods developed in animals can be translated to humans, which will be very important for the general aim of developing methods of in vitro derivation of eggs from pluripotent stem cells, which could permit much valuable research and ultimately help many more infertile women. However, the only true test of whether the in vitro grown oocytes were normal, namely to see if they would support fertilisation and early embryo development, has still to be carried out.”