<b>The role of heat shock protein 70 on oocyte apoptosis during vitrification</b>

The cryopreservation of animal and human oocytes has potential for developing assisted reproductive technologies (ARTs), especially as oocyte bank. One of the techniques used for oocyte cryopreservation is vitrification to avoid the critical temperature and reduce cell damage caused by the formation of ice crystals. Although the oocyte vitrification method is practical, applicable, efficient, inexpensive, and simple, further research is required because of the negative effects of temperature stress. Extreme temperature due to temperature changes from hot-cold-hot in the series of vitrification processes needs to be aware of damage to the structure of cell proteins and DNA. Extreme temperatures can cause stress to oocytes. Stress cells increase the need for heat shock protein 70 (HSP70) as a stress protein. The inductive or synthesized response of HSP70 is considered a protective mechanism of the cells to stress conditions, such as an extreme temperature change. The role of HSP70 in cell protection against extreme temperature changes during oocyte vitrification needs to be assessed by adding HSP70 supplementation into the cryoprotectant vitrification. In conclusion, HSP70 plays a pivotal role in cell protection against stress cells during oocyte vitrification. Fresh oocytes, in vitro maturated oocytes, and postwarming oocytes exhibited HSP70 and Cytochrome c expression. Supplementation of HSP70 into the vitrification medium was expected to suppress the activation of caspase 3, thereby maintaining the viability of oocytes during vitrification and decreasing the incidence of apoptosis after warming.