What is Cryopreservation?
Cryopreservation is the process of preserving living cells, tissues, or organisms at extremely low temperatures to maintain their viability for future use. This method is widely utilized in laboratories for storing biological samples and is a critical tool in reproductive medicine, where embryologists routinely freeze human eggs or sperm.
At low temperatures, the myriad metabolic processes within cells slow down significantly, effectively halting biological activity. This pause in cellular activity allows scientists to preserve the cells’ structural and functional integrity, ensuring they remain viable when thawed and returned to physiological conditions.
Cryopreservation: A Natural Evolutionary Strategy
The concept of cryopreservation isn’t exclusive to modern science—it has parallels in nature. During Earth’s history, species have endured extreme cold periods that forced them to develop unique survival mechanisms. Some plants and animals adapted to these conditions by withstanding freezing and desiccation, challenges that mimic those encountered in scientific cryopreservation.
However, freezing comes with risks. Cells can be damaged by processes such as extracellular and intracellular ice formation, as well as dehydration. Over the last century, extensive research has addressed these challenges, leading to the development of cryoprotective agents.
The Role of Cryoprotectants
Since the introduction of cryoprotective agents in 1948, significant advancements have been made in optimizing freezing techniques. Cryoprotectants help minimize freezing-related damage by preventing ice formation and stabilizing cellular structures. With proper formulations and protocols, once biological material is frozen, it can remain safely preserved for extended periods.
Cryopreservation has revolutionized biological research and medicine, offering a way to pause and preserve life until it is needed—a true marvel of science rooted in both innovation and nature’s resilience.
Advantages of Cryopreservation
Cryopreservation is the gold standard for long-term storage of biological materials, offering unparalleled convenience and reliability. By maintaining cells, tissues, or other biological samples in a frozen state, researchers and clinicians gain access to a stable repository of unaltered samples that can be used whenever needed
Key advantages of cryopreservation include:
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Preservation of Genetic Integrity:
Cryopreservation prevents potential mutagenic drift that can occur in actively dividing cells. This ensures the genetic and phenotypic stability of the samples over time, maintaining their original characteristics for accurate research or therapeutic applications.
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Cost and Resource Efficiency
Freezing samples significantly reduces the need for continuous, saving both materials and labor. This streamlined approach minimizes costs while maintaining the viability of critical biological resources.
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Facilitating Distribution
Frozen samples are easier to transport and distribute, enabling widespread sharing of valuable biological material. This is particularly beneficial in collaborative research and clinical applications, where consistent sample quality is crucial.
Cryopreservation has become an indispensable tool in the scientific and medical fields, providing a robust solution for safeguarding biological resources for future innovation and discovery.
Common Applications of Cryopreservation
Cryopreservation is widely utilized for the long-term storage of biological materials, serving various purposes across diverse fields. It plays a crucial role in biological research, cell therapy, and, perhaps most famously, reproductive medicine.
One well-known application involves preserving eggs retrieved from a woman's ovaries. This procedure is particularly beneficial for women undergoing cancer treatments, such as radiation therapy, chemotherapy, or certain surgeries that may result in infertility. Additionally, exposure to certain toxic substances can impair reproductive health, affecting sperm quality and male fertility. To address such challenges, well-established embryo and sperm banks have become vital for supporting future in vitro fertilization (IVF) procedures.
Cryopreservation is not limited to humans. It is also a valuable tool in animal research, particularly for maintaining research colonies. This process reduces costs and labor in animal husbandry, prevents undesired genetic drift, and provides a secure backup for preserving colonies and species.
Zebrafish and Cryopreservation
Zebrafish as a New Alternative Model (NAM) is increasingly recognized for its applications in various research fields, including toxicology, developmental biology and ecotoxicology. Zebrafish are particularly valuable for studying reproductive toxicity, offering unique advantages such as external fertilization and a high fertilization rate. Additionally, their use aligns with the principles of the 3Rs: Replacement, Reduction, and Refinement.
As the use of zebrafish in research grows, so does the need for effective cryopreservation programs. Cryopreservation helps reduce the number of live specimens housed in facilities and serves as a safeguard against potential accidents, such as fires, that could jeopardize the survival of zebrafish colonies.
At Biobide, we have developed and validated an assay to evaluate the reproductive performance of zebrafish following sperm cryopreservation. This begins with an in vitro analysis to assess sperm quality from a thawed frozen sample. Using microscopy combined with a Computer-Assisted Sperm Analysis (CASA) system, we measure key motility parameters, including progressive motility, curvilinear velocity, and linearity. Once these parameters meet our quality standards, an in vitro fertilization assay is conducted using healthy female zebrafish.
The successful outcome of this process ensures that the quality of the cryopreserved sperm is preserved, allowing the colony to remain safely stored and available for future use whenever needed.
References
Diogo, Patrícia et al. “Electric Ultrafreezer (− 150 °C) as an Alternative for Zebrafish Sperm Cryopreservation and Storage.” Fish physiology and biochemistry 44.6 (2018): 1443–1455. Web.
Caetano Da Silva, Caroline et al. “An Easy Method for Cryopreservation of Zebrafish (Danio Rerio) Sperm.” Zebrafish 16.3 (2019): 321–323. Web.
Diogo, Patrícia et al. “Selection Criteria of Zebrafish Male Donors for Sperm Cryopreservation.” Zebrafish 16.2 (2019): 189–196. Web.
