Cryopreservation

• Cryopreservation (Cryo: icy cold or frost; Preservation: Storage without deterioration) refers to the storage of living material at ultra-low temperatures below -135°C without losing its vitality in a manner that stops biological time and aging. The goal is to preserve the material’s vitality so it can be revived later.
  
• Freezing is generally detrimental to living organisms and cells due to the damaging effect of the freezing process, particularly ice formation, changes in osmolarity, and oxidation process. Read more about Detrimental Effects of Freezing on Cells and Tissues
• Cryopreservation procedures mitigate these damaging effects through specialized procedures and the use of cryoprotective agents.
• Cryoprotective agents are substances that protect cells during freezing by reducing ice crystal formation and minimizing other forms of cellular stress. Read more about: Cryoprotective Agents
  
• Cryopreservation has been successfully applied to a wide range of biological materials, including individual cells (like sperm, eggs, and blood cells) and tissues.
  
• The optimal cryopreservation protocol depends on the biological material’s complexity and intended applications, as complexity directly influences preservation success.
• Generally, isolated cells are more easily preserved and exhibit higher recovery rates than more complex multicellular tissues and organs. Preserving entire organs for transplantation remains a significant challenge in the field. 
• Classical cryopreservation procedures involve the slow cooling of biological samples in the presence of low concentrations of cryoprotectants to minimize ice crystal formation, thereby reducing cellular damage. This method is commonly used for the preservation of sperm, blood cells, and various types of tissues. For instance, sperm banks utilize slow freezing techniques to maintain the viability of sperm for future use in assisted reproductive technologies. 
• In contrast, recent advancements in cryopreservation have introduced vitrification, which employs high concentrations of cryoprotectants and involves rapid cooling. This process transforms biological samples into a glass-like state without ice crystal formation, making it particularly effective for the preservation of oocytes, embryos, and certain tissues. Vitrification has become increasingly popular in fertility clinics due to its ability to enhance survival rates upon thawing.
  
• While cryopreservation is a human-developed technique, some organisms exhibit natural freeze tolerance. These organisms, such as the wood frog and gall fly larvae, have evolved mechanisms to survive freezing temperatures without human intervention. Studying these natural examples can provide valuable insights for improving cryopreservation techniques. (read more: Natural Cryopreservation)
  

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