Procedures involved in Cryopreservation

Cryo-preservation or cryo-conservation is a process where organelles, cells, tissues, extracellular matrix, organs, or any other biological constructs susceptible to damage caused by unregulated chemical kinetics are preserved by cooling to very low temperatures (typically-80 °C or -112 °F using solid carbon dioxide or −196 °C (−321 °F) using liquid nitrogen). At low enough temperatures, any enzymatic or chemical activity which might cause damage to the biological material in question is effectively stopped. Cryopreservation methods seek to reach low temperatures without causing additional damage caused by the formation of ice crystals during freezing. Traditional cryopreservation has relied on coating the material to be frozen with a class of molecules termed cryoprotectants. New methods are being investigated due to the inherent toxicity of many cryoprotectants. Cryoconservation of animal genetic resources is done with the intention of conservation of the breed. Cryopreservation plays an important role in medically assisted reproduction. Cryopreservation allows storing sperm, eggs, embryos and ovarian tissue for fertility preservation for a longer duration.  Fertility preservation by cryopreservation is recommended for individuals who will undergo treatment that can affect their fertility, such as radiotherapy, chemotherapy, or major surgery on or in the vicinity of reproductive organs, who are at increased risk of premature loss of eggs or sperm due to certain genetic conditions e.g. Klienfelter syndrome in men or Turners syndrome in women, who are going through assisted conception treatments and have supernumerary embryos that need to be saved for later use, who produce a very low sperm concentration and therefore will be best served by having a frozen sperm back up, in case no sperm available in fresh ejaculate on the day of egg collection, who wish to delay fertility for social/personal reasons.

rolex submariner fakes

Preserving the embryo for later use is the primary objective of embryo freezing. Therefore, the embryo has to be maintained in such an environmental condition that it does not die. The steps involved in freezing or cryopreservation of the embryo are:

Embryo Selection-As part of the IVF process, the woman is medically stimulated to make more eggs. The man also gives a higher number of sperm cells. When both are mixed, several embryos often tend to develop. The doctor usually transfers one to four embryos into the woman while the rest is left over. Here, the healthiest embryo or embryos are selected so that it can be stored for future use.

Removal of the water content-The selected embryo cannot be frozen directly without replacing the water content within the cells. This is because when it is kept for freezing the water content inside the cells also freezes and crystalizes. the crystal formation can cause expansion which can burst the cell open, causing it to die.To prevent this from happening, cryoprotectants are used to replace the water content inside the cells.

Embryo Freezing-There are different types of freezing methods like slow freezing method, rapid freezing method, dry freezing method.

Storage-It is also important for the maintenance of the material at a specific temperature. In general, the temperature is kept - 70 to - 196°C. Prolonged storage is done at the temperature of -196 °C in liquid nitrogen. A continuous supply of nitrogen is needed to prevent damage.

Thawing- The thawing process is usually carried out by plunging the vials into a warm water bath with vigorous swirling. It also causes the vials to get transferred or move to another bath at 0 °C

Washing & Reculturing- The preserved material is washed to remove the cryoprotectant. Furthermore, the material is recultured in a fresh medium.
Measurement of Viability-Due to storage stress, there is a possibility of cell death. The presence of viability can be seen in most cases.

Media Contact:
Andrina Williams
Journal Manager
Journal of Fertilization: In Vitro
Email: fertilization@medicalresjournals.com