The idea of tissue storage and preservation has been around for quite sometime now. Since the 1800s to be exact. But how did the idea of freezing to very low temperatures to preserve cells evolve through the test of time? 

It was already known that organic material could be preserved using freezing temperatures. With experiments, the preservation methods have come a long way from snow to liquid nitrogen. Using modern methods, the temperature was chosen around -80°C when using CO₂ , whereas the temperature is taken around -196°C while using liquid Nitrogen. The idea was to preserve the cell’s contents without actually forming ice crystals that could severely and irreversibly damage the cell contents. 

Cryoprotectants were tested out that would actually help the process rather than harming it. Let’s take a walkthrough into the history of cryopreservation: the contributions of the researchers associated with it, and know how the modern methods of cryopreservation came to be.

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• In 1953, James Lovelock suggested that osmotic stress could be a reason for damage in red blood cells during freezing; there is an increasing salt concentration in the cell that causes damage. However, when only 60% of the water content is crystallised, the cells do not suffer damage. 

• 10 years later, Peter Mazur from Oak Ridge National Laboratory, U.S. demonstrated that if the cooling was slow enough to let a sufficient amount of water content exit the cell during the freezing process.

• It was in 1953 when the sperm cells were cryopreserved for the first time and 25 years later, embryos were cryopreserved. With subsequent experiments and years later in 1986, Dr. Christopher Chen of Singapore achieved the world's first pregnancy using frozen oocytes. 

• In 1999, a milestone was achieved in the world of egg freezing when the world’s first live birth was reported  by Dr. Lilia Kuleshova, who was the first scientist to achieve vitrification of human oocytes. 

Cryopreservation has a bright future in Assisted Reproduction. Freezing of eggs, sperm and embryos is very helpful for couples wanting to delay pregnancy or facing infertility. With time, effort and a lot of experimentation, the future will bring us more access and utility in this technology. Freeze your eggs, not your dreams! 

References

• Pegg D. E. (2002). The history and principles of cryopreservation. Seminars in reproductive medicine, 20(1), 5–13. https://doi.org/10.1055/s-2002-23515
• Betsy, J., Kumar, S. (2020). Cryopreservation: History and Development. In: Betsy, J., Kumar, S. (eds) Cryopreservation of Fish Gametes. Springer, Singapore. https://doi.org/10.1007/978-981-15-4025-7_6
• Whaley D, Damyar K, Witek RP, Mendoza A, Alexander M, Lakey JR. Cryopreservation: An Overview of Principles and Cell-Specific Considerations. Cell Transplantation. 2021;30. doi:10.1177/0963689721999617
• Iussig, B., Maggiulli, R., Fabozzi, G., Bertelle, S., Vaiarelli, A., Cimadomo, D.,… Rienzi, L. (2019). A brief history of oocyte cryopreservation: arguments and facts. Acta Obstetricia et Gynecologica Scandinavica. doi: 10.1111 / aogs.13569 

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