Cryopreservation of Animal Colonies
An invaluable tool in an era of worsening storms and other extreme events.
During 2012’s Superstorm Sandy, as people were fleeing flooded apartments and much of New York City went dark, the auxiliary generators at New York University’s Langone Medical Center also failed.
The flooded hospital was forced to evacuate more than 300 patients, but that was not the only section severely impacted. The storm destroyed their vivarium housing rodents used for medical research. It took years—and many generations of breeding—to rebuild the colony, which included animals used to study melanoma and other diseases.
NYU is not the only vivarium to have faced a weather-related natural disaster. The University of Houston’s vivarium was flooded during Hurricane Harvey, which dumped several feet of rain on the Gulf Coast. And Louisiana State University’s vivarium was all but destroyed during Hurricane Katrina.
Most scientists agree that climate change is helping to turn bad storms into catastrophic ones with greater frequency. So how can vivariums safeguard their colonies—primarily rodents that are the workhorses of biomedical research—in the event of a natural disaster? One way is by freezing the biological material needed to create new generations of animals and storing it in less high-risk locations.
Cryopreservation, as the technique is known, permits low temperature maintenance of embryos and sperm that are used to genetically engineer a mouse or rat. To cryopreserve one needs a freezing agent—glycerol is one example though companies are now making their own proprietary formulas—that preserves the cells under colder conditions. The embryos and sperm, as well as cell lines, can be stored for extended periods of time under the right temperatures.
Cryopreservation helps to minimize damage to biological material during low temperature or freezing. And it ensures that the animal research can continue, without disruption, when disasters, both human and natural, threaten animal colonies.
Additionally, cryopreservation of gametes—the cells containing half the chromosomes necessary for reproduction—and embryos prevent genetic drift—tiny genetic variations that can alter animal stock. It safeguards the genetic integrity of valuable strains and offers a viable alternative to maintain an active breeding colony, which as we know from the examples cited above, can be at risk during violent storms.
Cryopreservation also increases generation time and allows for further contribution of genetics past a rodent’s natural life span. By cryopreserving a line, you can keep the genetics of a valuable strain “alive” longer than with a real animal. However, if you freeze sperm or embryos, you can keep that line around for decades, thus extending the life span or generational interval.
Lastly, genetic stock is easier to transport, disease transmission goes down, and, perhaps mostly importantly, recovery of stock following a natural disaster is much faster. If you use cryopreserved material instead of shipping live mice, you have less chance of bringing pathogens into a research facility. The live mice can be vectors that carry disease and contaminate colonies, while the biological material is clean.
Of course natural disasters are not the only reason to cryopreserve. Animal husbandry errors can cause genetic drift of existing colonies and genetic contamination of lines. Colonies can also be affected by power outages, HVAC failures and pathogen contamination.
Pandemics, such as COVID-19, are also a reason to preserve because when people are not able to get to work, colonies must be culled. If the labs had cryopreserved their lines they would save valuable research material.
How to cryopreserve
There are three main methods used in cryopreservation. One method occurs slowly at a controlled pace, another relies on rapid freezing. A third method, vitrification, uses high concentrations of a cryoprotectant that transforms the substance into a glass-like state, preventing the formation of ice crystals, which can prevent damage to an embryo during the freezing process.
Embryo cryopreservation is the most commonly used method for preserving genetic stock and is provides the fastest way to recover a line following a disaster. A minimum of 150-300 embryos are routinely frozen to preserve a line. About 40 embryos can be stored in a single straw about the size of a pen. Embryos can be stored for an extended period of time—in locations far from the vivarium to minimize risk—and the genetic material can be transported easily to collaborators hundreds of miles away.
But sperm are also cryopreserved and because they require only a few donor animals, about two males, this method is typically less expensive than embryo cryopreservation. Sperm cryopreservation can also be completed more quickly than embryo cryopreservation and is a great method to quickly preserve a line especially during a disaster situation.
At the end of the day, all animal research facilities should have a disaster plan that carefully outlines the necessary steps needed to secure their facilities and colonies. And they should consider cryopreservation. Over the long haul, it could help overcome a natural and human disaster, and save laboratories time and money.
This is part of Eureka's year-long series on how climate is impacting the pharma industry.