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Advantages And Disadvantages Of Cryopreservation Of Ovarian Tissue

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2.3.5: Advantages and disadvantages of cryopreservation of ovarian tissue:
An alternative strategy for storing the female germ cells is cryopreservation of ovarian tissue. This method allows the storage of a large number of oocytes (within primordial follicles). Unlike fully grown oocytes, oocytes in primordial follicles tolerate cryopreservation very well. Several characteristics make them less vulnerable to cryodamage. The most important of these features are:
(a) the small size of the oocyte and its supporting cells.
(b) low metabolic rate of the oocyte.
(c) the absence of zona pellucida (ZP) and granules devices cortices.
(d) the small amount of intracytoplasmic lipids sensitive to cold.
(e) They do not have the pin division, ZP and cortical …show more content…

Since biological membranes prevent the formation of ice nuclei in the intracellular components, ice formation occurs in the extracellular space (David et al., 2012). To maintain the long-term vitality, living cells must remain suspended for an indefinite period and then return to the normal metabolism. Phase extracellular ice will be increased by prolonged cold, so the concentration of salts in the non-frozen part will be increased extracellular (Vahid and Rahim, 2012). In the freezing processes, these changes are reversed with the thermodynamic equilibrium between the intracellular and extracellular environments (Karow et al., 1997;. Aslhan et al, 2014). For long-term preservation of simple or complex cell structures, liquid nitrogen (-196 ° C) is used in which the intracellular chemical reactions stop at this temperature (and Demircia Shaeed, 2002).
The only danger that can occur for frozen cells is DNA damage [Jain John2006]. Adding cryoprotectants compounds in maintenance environment of tissues, freezing and thawing rate control can reduce cell damage [Mazur and Physiol 1984]. The biggest risk may occur when the temperature drops to -196 ° C or rises to 37 ° C. Seeding is essential to reduce the temperature changes at the time that ice cores are formed. These changes are due to exothermic reactions (caused by the formation of ice crystals (and Demircia Shaeed, …show more content…

During freezing, because the salts out of the portion of the frozen water, the concentration of electrolytes and other salts can be increased to very high levels, so that it can be toxic for proteins intracellular. Thus preventing the formation of ice crystals and toxic effects of the solution to the freeze period are among the fundamental objectives of successful cryopreservation (John Jain et al., 2006).
During thawing, the cells are placed in the wash solution, so that cryoprotectants can be washed and removed. It can lead to conditions opposite to what was at the time of the addition of this material. The cells are swollen due to the water inlet, and slowly shrunken after removal of cryoprotectant. When cryoprotectants and the flow of water reaches equilibrium, cell volume reaches its maximum size (Karlsson et al., 2000).
When the cast is quick, sudden drop in extracellular osmotic pressure can lead to a rapid transfer of free water in the cell, and then can lead to swelling and damage to cells; the phenomenon which is called osmotic shock. When thawin is slow, there is the risk of free water thawed and re-crystallization, leading to further damage. Chemical additives Therefore, all freezing methods are used, which are known as cryoprotectants, to prevent cellular damage (Jain John et al.,

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