Cryopreservation is the freezing of male and female germ cells, as well as embryos for the purpose of storing them for an indefinite time. Sperm, oocytes and embryos are amenable to deep freezing (up to -196 degrees Celsius) in liquid nitrogen.
Before freezing, all moisture is removed from the cells, since it is fatal when frozen. Store frozen material in special reservoirs - Dewar vessels. All portions are labeled, embryos are stored 1-2 in vitro.
What is cryopreservation of sperm and oocytes?
Sperm can be frozen if IVF is planned, but on the day of puncture the man will not be in the clinic for one reason or another. A bad spermogram is another reason to resort to cryopreservation of spermatozoa. This makes it possible in several stages to collect the right amount of sperm and successfully carry out a program of in vitro fertilization.
The egg can be frozen for those who have an oncological disease. Before the radiation and chemotherapy, which most often lead to the loss of fertility in women , you can make a stock of eggs so that in the future she could have children.
Frozen semen
Collected for freezing the sperm check. It undergoes a trial freezing and defrosting. If the indicators are good, and the test for whether it is possible to freeze the sperm was successful, the newly collected material thickens and increases the concentration, processed properly and placed in a container. The container is a thin plastic tube of small diameter. This tube is labeled so as not to be mistaken when fertilized with frozen semen.
Cryopreservation of oocytes
Collection of eggs for freezing is a long and more complicated process than sperm. A woman is given a hormonal stimulation of the ovaries so that several oocytes mature at the same time. After this, there is a puncture of eggs, selection of the most viable. They are treated and the excess liquid is removed, then placed in a special container and frozen with liquid nitrogen.
Cryopreservation of embryos
Embryos are frozen for several purposes. Firstly, in order that, in the case of an unsuccessful attempt, IVF could be tried again without re-stimulating the ovaries and puncturing the oocytes.
In addition, embryos undergo cryopreservation in cases where a woman does not tolerate the transfer of embryos (ovarian hyperstimulation syndrome). Immaturity of the endometrium is another reason for freezing embryos. Embryos in this case develop several days, then the best of them are selected and amenable to freezing. When the woman's endometrium is ready for embryos, the transfer of frozen embryos takes place.
Frozen embryo is stored as long as you want. Of course, the process of freezing and defrosting is stress for embryos. But modern methods allow not only to save a larger number of frozen embryos in a viable state, but also to guarantee their normal
Conditions for cryopreservation of embryos
First, only the best embryos give in to frost - with the highest quality indicators. Secondly, it occurs at a certain stage of their development: in stages 2, 4, 8 cells and blastocysts.
Embryos, whose indicators are defined as bad, do not lend themselves to freezing, as they have the property of degrading - breaking down. Sometimes good embryos are also destroyed - this is the price for their freezing and subsequent defrosting. But there are always several embryos frozen, so some of them remain viable after defrosting.