Vitrification of embryos on individual carriers

This article will deal with such a concept as vitrification of embryos. Dr. Masashige Kuvayamoy invented this method in cryotopes in the year 2000. The first child was born due to vitrification embryos in 2003. Survival of oocytes was increased by 98 percent.

At half of women who are prescribed in vitro fertilization, embryos remain. For them, cryopreservation is carried out, which saves money for patients. It is much easier to unfreeze and transfer embryos than to perform an in vitro fertilization procedure anew. Also this is a kind of insurance in case the woman does not become pregnant. Cryopreservation has an indisputable advantage - the death of viable embryos that are left after the protocol is prevented.

Ontogenesis

The course of the subjective development of the organism, or ontogeny, originates from the moment of fertilization and ends with its death. This movement is continuous in time and has an irreparable character. And we can not stop it or slow it down. But there are exceptions in nature. These are plants, invertebrates and even some elementary vertebrates, which at low temperatures do not exhibit the properties characteristic of living organisms.

What is anabiosis?

Vitrification of embryos will be discussed below. Individual period of calmness is called anabiosis. So, for example, many Siberian animals survive a temperature reaching -90 degrees, and almost complete dehydration. When studying this period of ontogenesis in natural conditions, the question arises of the possible use of lower temperatures for partial and reversible interruption of the functioning of higher vertebrate beings, including humans.

Cryopreservation

Cryopreservation is an effective method of suspending biological processes in cells by acting at a low temperature. At the same time, the vital activity of cells during heating is maintained. By popularity, this method is inferior to vitrification of embryos. 1 cryotope (labeled cryo-carrier) contains from 1 to 3 embryos.

For example, when performing a procedure such as IVF, the best action is to move to the uterine cavity no more than two embryos. The remaining qualitative embryos can be cryopreserved for use in the future. They can also be used to re-conduct IVF after a while, if the procedure shows a negative result. With such purposes, vitrification of embryos on individual carriers is carried out.

In some cases, all embryos are frozen. For women who have ovarian hyperstimulation syndrome induction of superovulation, this is most often done. Who else is recommended for freezing? Patients suffering from oncological diseases, in particular before the procedure of chemotherapy or radiotherapy. Then, these embryos are transferred to the uterine cavity. Frost is indicated for all those who are less likely to become pregnant after IVF. This may be an endometrial polyp, an insufficient thickness of the endometrium by the time transfer is planned, dysfunctional bleeding.

Stages of freezing

Embryos are frozen at various stages:

• Fertilized ovum (zygote);
• Stage of fragmentation of embryos;
• Blastocyst.

At the moment, there are two ways to freeze embryos.

Slow freezing

Vitrification of embryos is performed with slow freezing. This method was proposed back in the 70's and is one of the first classical methods of embryo freezing. It is based on slow cooling with a constant speed. After the embryos are stored in liquid nitrogen.

But it should be noted that with slow freezing in a cryoprotective solution, microscopic ice crystals are formed, which adversely affect the cells of the embryo. This can provoke partial or complete destruction of the biomaterial during heating. The number of embryos successfully transferred in the process of slow freezing and warming is about 70 percent.

Vitrification

After 2010, a new and more effective method of cryopreservation - vitrification - began to be applied. In comparison with the previous method, this is an ultrafast way of freezing the biomaterial. Most often, vitrification of embryos after PGD (genetic diagnosis).

With this procedure, a cryoprotective solution, where embryos are placed, does not form ice crystals when frozen. Thus, the probability of embryo damage is reduced. The priority of this method is not only the method of freezing, but also the percentage of survival of embryos after warming. According to statistics, the number of survivors after the vitrification process of embryos is not less than 95 percent.

What happens after warming up?

After warming, embryos almost do not differ from ordinary embryos. They as well get accustomed and develop. When warming, all embryos undergo an auxiliary hatching process. In carrying out this action, the surface layer of the embryo is separated by a laser beam at the desired and safe angle. This facilitates the release of the embryo from the membrane and increases the possibility of successful transplantation into the uterine cavity.

Freezing allows the storage of embryos for a long time. This process is economically advantageous, since the price of preservation, warming and implantation of the embryo into the uterine cavity is less than the repeated process of in vitro fertilization.

The vitrification is considered as a stepwise transition, where the cold solution is cooled below the glass transition temperature. At the same time, it remains amorphous, receives a glass structure and a quality similar to crystalline solids. Thus, both living cells, and even the whole embryo turn into "glass". The vitreous structure of the liquid during vitrification is obtained because of its rapid cooling, that is, the entropy of the liquid decreases over a shorter time interval than the entropy of the necessary crystal structure.

In simple words, the liquid does not freeze when its entropy approaches the entropy of the crystal. But in order to correctly vitrify the living organism, it is necessary to achieve a rate of temperature decline of ≈ 108 ° C / min, which in practice is impossible, because the cryogenic liquid used has insufficient temperature for this, and the vitrification solution can not be used in a smaller volume than the volume Oocyte. This all involves vitrification of embryos. What is it now has become more or less clear.

Scientists were able to prove that an increase in the environment for the freezing of cryoprotectants makes it possible to quickly reduce the rate of freezing. Hence, with a density of 10% ethylene glycol and propylene glycol, the rate is significantly reduced, with 40 percent density, vitrification is possible with a cooling rate of 10 ° C / min, and at 60% the rate drops to 50 ° C / min. But with the increase in the density of cryoprotectants falling into the environment, their negative influence on the freezing of biomaterials increases. Slow freezing provokes the accumulation of chilled water in the biological body and the intracellular element. This condition is observed because of the strong dehydration of the cell with the appearance of extracellular ice.

Accordingly, when the glass-like structure is obtained, the chemical and physical processes of dehydration of the organism are discontinued. Despite the fact that vitrification of embryos (which it was described in detail above) is a rather difficult physical system, the materials of such a structure can be found in our daily life (glass, silicone and so on).

Vitrification of embryos: reviews

This method only collects positive feedback. The vitrification procedure is feasible. But it has many features at different stages of development in ECO-laboratories. Vitrification is not the newest method of cryopreservation of living cells. It is the last stage of slow freezing. Today, many women have the opportunity to give birth to a child through scientific development.

conclusions

Due to the work of many scientists, vitrification can be carried out without using an expensive programmed freezer, but with the use of simple equipment that is controlled by the operator. Thus, the method is simplified and the final result is improved. Despite the great achievements in cryopreservation, the realization of the correct conservation of living organisms at low temperatures is impossible today.