Cryopreservation (freezing) is the process of storing to preserve structurally intact living gametes (sperm and egg cells) and reproductive tissues for later use or donation. Sperm freezing and embryo freezing are the oldest and most successful cryopreservation processes at present. Mature oocyte cryopreservation, which has become popular in recent years, is an increasingly successful procedure in terms of saving a woman's ability in getting pregnant in future when her ovarian reserve diminishes. Currently, reproductive tissue freezing is at the stage of scientific research and it is reported that it has been successfully applied in some centers.

For whom cryopreservation is recommended?

• For couples willing to use their unused healthy embryos in future after IVF treatment
• For persons or couples, who are willing to have a baby in future but having concerns about a decrease in age-related fertility
• Before undergoing cancer therapy, for patients who are willing to preserve their own healthy gametes or embryos and fertility after treatment
• For those who want to facilitate the synchronization between the donor and recipient in donation treatments

The success of freezing procedure depends on directly the quality and safety of the lab conditions and the reliability of the freezing technique. Vitrification is a technology that is used to freeze gametes, embryos, and reproductive tissues so that they can be stored for later use. Ice crystal formation which is very damaging to gametes and embryos is one of the major hurdles of conventional freezing techniques. Compared to conventional freezing techniques, vitrification works on a completely different principle for cryopreservation without ice crystal formation. Vitrification Technique is highly reliable and provides opportunity to freeze the cells by applying high concentrations of cryoprotectant followed by ulta-rapid cooling to solidify cells into a "glass-like formation". Cells are put in a special solution called a vitrification medium and that solution is then cooled so quickly that the structure of the water molecules doesn’t have time to form ice crystals. Instead, in a single instant, the cells pass from ambient temperature to the temperature of liquid nitrogen, which is -196°C, and instantaneously solidify into a glass-like structure.  Thus, the integrity of the cells is preserved without being damaged.

n this technique, the material to be frozen is first put into “balancing solutions”, allowing the water in the cells to leave the cell by osmosis. Subsequently, the shrunken cells are put into the special solution called “vitrification medium” which allows the cells to regain their former volume by means of cryoprotectants, which prevent damage to cells during freezing.Finally, the cells are suspended into liquid nitrogen tanks with the storage apparatus on which they are loaded. There is no time limit for the storage of cells or tissues. The thawing process, which is one of the most important stages of the vitrification technique, needs to be carried out quickly at the appropriate temperature and conditions.The post-thaw survival rate in the vitrified gametes, embryos, and reproductive tissues is almost 100%.