Vitrification: the cold revolution
Vitrification is generally associated with delaying maternity. It involves preserving eggs at low temperatures so that they may be used in the future. This is, in itself, astounding since it enables gametes to be preserved by means of advanced and ultra-rapid cell freezing so that they may be used sometime in the future. The uses to which this technique may be put are so varied and numerous and have changed the work environment in the most prestigious of fertility clinics to such an extent that experts have no doubts about referring to vitrification as a ‘revolutionary’ procedure.
“We could say that cryopreservation is currently the most important aspect of any assisted reproduction clinic” assures Dr Jorge Ten, head of the Reproductive Biology Operational Unit at Instituto Bernabeu in Alicante. In the words of this expert, this technique “has changed enormously over the last 6 to 8 years”. Vitrification was initially carried out using “slow freezing techniques which caused cell damage” in the oocyte. This cell, “in the case of women, is the largest in the human body and has the greatest content in water. Therefore, when frozen, it produced poorer results due to the formation of ice crystals which damaged its structure”. The ice crystals which formed as a result of the aforementioned slow freezing and the high water content in the cell meant that survival rates were “between 20 and 30%. Almost no oocytes survived”.
Scientific research started bearing fruit towards the end of the 20th Century or early year 2000 when ‘new protocols’ came into place, improving the freezing process and optimising results. Its use became widespread across assisted reproduction clinics and, from that point forward, with the vitrification technique or ultra-rapid freezing fully developed, the initial low survival rate and cell damage “changed”.
But specialisation, quality and intense training procedures for employees are necessary if vitrification is to be carried out in assisted reproduction clinics. Dr Jorge Ten explains that in the case of Instituto Bernabeu in Alicante there is “an important learning curve because the techniques are extremely difficult. Embryologists need to be trained”. What’s more, as the clinic in Alicante’s personnel explain, “integrity” is essential in this technique since healthy, high quality cells have to be frozen so that they can get through the process without suffering any damage. Thanks to this commitment to ethics, professional practices and training and the resulting application of the cryopreservation techniques in all Instituto Bernabeu branches, “survival rates are at around 95%” in this clinic, above the rate established by “quality standards which is between 85 and 90%”.
The need to cryopreserve oocytes “began with cancer patients as a means of preserving their fertility”. “Chemotherapy and radiotherapy treatment” can damage or deteriorate “the ovary germinal epithelium”, leaving it “incapable of producing eggs”. Thanks to freezing techniques, women can preserve oocytes and use them in the future to get pregnant once the treatment has come to an end.
With time, the technique’s applications have increased and have been adopted in other areas of assisted reproduction medicine and, as such, provides solutions for a wide range of cases. One such example is the decision to delay motherhood for social reasons. Compared with the past, “nowadays, women delay motherhood” and this means “that more and more women over 35 now come to us to request that their eggs be frozen so that they can use them later on”. Dr Jorge Ten explains that age is connected to “chromosomal abnormalities and the sooner oocytes are frozen, the better. There will be fewer abnormalities and they will be healthier”. The solution would be to cryopreserve when women are even younger but this has not yet become socially accepted. Ten explains that it’s a matter of information. “Women need to know that they can use their oocytes in the future if they cryopreserve them” when they’re young.
Cryopreservation is also of use in other aspects of assisted reproduction. Nowadays, thanks to this technique, “which we have been putting into practice in IB for many years, we have been able to optimise results to the point that in conventional treatment such as In Vitro Fertilisation (IVF), we have the option of not transferring fresh embryos but of freezing them and the results are very favourable”. This is very useful in cases where there are specific problems in the endometrium which are heightened when it goes through ovarian stimulation. If embryos are cryopreserved, they may be transferred later on “which gives the endometrium time to get over the treatment and improves implantation possibilities”, explains IB.
Ultra-rapid freezing has also enabled Instituto Bernabeu in Alicante “to have egg donation and oocyte cryopreservation banks for over six years” which provides “back-up whenever needed”. As well as the fact that the technique does not harm the cells, the passing of time does not have a damaging effect, either. An oocyte can be cryopreserved for an indefinite period of time without causing abnormalities. With reference to the egg bank, Dr Jorge Ten explains that they continue “to work with fresh oocytes but it’s a back-up” for when the unexpected occurs.
Another use of vitrification is in the case of foreign patients or couples since “we can freeze the oocytes and semen sample and carry out treatment whenever convenient. That is, when it’s the right time and the patient is available to travel” to the facilities in Alicante. This also makes it very practical for all couples, not only foreign ones. In those cases in which pregnancy is not achieved in a first IVF attempt, it’s not necessary to go through oocyte extraction all over again. “Transfer can take place following simple hormonal preparation” using the couple’s previously frozen embryos, explains Instituto Bernabeu in Alicante. Additionally, that same couple, following successful pregnancy and the birth of a child, “could once again use the frozen embryos when the time comes to try for a brother or sister”, they add.
The uses to which cryopreservation may be put are many and cover different areas of medicine, reproductive biology, gynaecology and also a more social side. Thanks to this technique, women can hold on to their fertility. The cold revolution – ultra-rapid freezing – has once again proven that scientific progress means life.