From a Backup Technology to a Strategy-Outlining Approach

The Success Story of Cryopreservation

Gábor Vajta; Anikó Reichart; Filippo Ubaldi; Laura Rienzi

Disclosures

Expert Rev of Obstet Gynecol. 2013;8(2):181-190. 

In This Article

Setbacks

According to many experts, in contrast to the situation 20 or even 10 years ago, setbacks hampering the successful application of vitrification are mostly of human and not biological or technical origin. Problems occur on different levels and for different reasons.

Academic Environment

As has happened many times before in science, applied research – under the pressure of the everyday need – has reached a big step ahead, while academic science has watched the advancement with disbelief, criticism and counterarguments, hampering rather than supporting the advancement. So far, most techniques and improvements have been introduced by using an empirical approach (we have to admit, not only in vitrification,[2] but also in slow-rate freezing[24]), justifying the statement that these techniques lack the required scientific background. On the other hand, providing this background is probably the task of basic science; therefore, those who criticize clinical embryologists should perhaps invest more work to support – at least retrospectively – the practical application.

Industrial Support

At least 13 kinds of industrially produced carrier tools and at least ten kinds of solutions are available on the world market. Approximately two-thirds of the available solutions have hidden components or hidden concentrations. Many laboratories (surprisingly mostly in the developed countries; and not too surprisingly some of the best laboratories are among them) work with in-house media – may the authors say fortunately, as these groups must provide an exact composition of media in their publications. The variations even in the basic equilibration and dilution parameters (temperature, concentration, quantity of media and time of exposition) are simply endless, and different parameters may be suggested for different developmental stages as well. The description of the methods in research papers are often insufficient to properly reproduce the given procedure, and reviews – including this one – talk about 'vitrification' while citing bulk results achieved with the most diverse technologies. On the other hand, new techniques are often published as breakthrough, while the actual achievements hardly approach the overall efficiency of an established, properly applied 'old' vitrification system, and the so-called 'controls' of the inventors are below any acceptable level – a shame for both authors and reviewers.

Legal & Mental Barriers

Problems related to the introduction of new techniques are also widely known and frequently discussed in assisted reproduction.[80,81] Vitrification seems to be an extreme example of these difficulties. Although the report of the first human pregnancy from a vitrified embryo was published in 1997[11] and in 2005, 2138 births were reported from a single Japanese clinic after blastocyst vitrification,[44] the first English baby born from a vitrified embryo created a press sensation in 2008, and the first French baby born after embryo vitrification was only reported in 2012. As mentioned earlier, the basic scientific knowledge regarding the effect of various vitrification techniques did not rapidly increase during these years. Almost all existing successful vitrification techniques, solutions and tools were available 12–15 years ago, and the latecomers profited from the empirical experience of the pioneers by proving the harmlessness and efficiency of the procedure. We are all responsible for the delay in the proper application of efficient techniques for human oocytes and blastocysts worldwide. This delay has resulted in many missed opportunities, and many families who could not obtain their ultimate goal. For many of them, it is too late now. We may refer many factors, but it was our fault as well, and we have to make much more effort to avoid such delays in the future.

Scientists' Performance

According to the rough estimation of authors – based on their extensive laboratory and international experience – approximately 95% of problems that occur during vitrification outcomes are related to technical failures and human factors. In fact, none of the existing vitrification methods are perfectly standardized and minor deviations may result in profound differences in the outcome. There are dozens of almost negligible small details that should be acquired with careful learning or through a series of frustrating fiascos.

Vitrification is seemingly a primitive procedure consisting of the transfer of samples from one solution to the other, then loading on or in a simple tool and immersing this tool into liquid nitrogen. Warming is just mirroring of the vitrification procedure; the carrier tool is removed from the liquid nitrogen, immersed quickly into a warm solution, then the samples are expelled and transferred into a series of diluent mixtures before culture. As tools have to be vitrified and warmed individually, and the maximum number of loaded oocytes or embryos is one, two or three, depending on the supposed need at a single warming, in an average-sized embryo laboratory, long series of identical manipulations – three to 15 or more repeats a day, for 15–20 min each – are required. In contrast to the fascinating and highly respected intracytoplasmic sperm injection, vitrification is often regarded as boring for a senior embryologist and the work is soon passed to the least experienced young beginner, all with negative consequences.

According to the experience of the authors, problems that occur in this situation are quite varied; inaccurate information (including basic mistakes, such as wrong order number, inappropriate storage or wrong concentration of chemicals, misreading of instructions, and so on), low level of theoretical and practical preparedness (either that of instructors or students, or both) and low level of motivation and attention may amplify the effect of previously mentioned problems. The technical support provided by most companies is less than basic and embryologists are usually left alone. They are surrounded by competitor clinics, without hope to consult about details and have very few chances to approach the level published in international journals. The few experts in the field may resolve the problem at the very first glance, but most of the on-field workers are completely unable to troubleshoot or maintain a consistently high efficiency.

In summary, quite in contrast with its importance, our impression is that in parallel with the confusion of terms and definitions, the whole area is more or less disorganized and lacks the required and expected professionalism. It is probably the robustness of the approach and the tolerance of the oocytes and embryos that helps to overcome the challenges created by the frequent improper application.

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