- Ultrafast Embryo Cryopreservation: Cornell researchers showed 30-fold faster cooling can prevent ice formation in bovine embryos.
- Improved Post-Thaw Viability: Fast-cooled embryos developed more like fresh embryos and performed better than standard-frozen embryos.
- Biobanking Applications: Findings may support embryo storage for livestock breeding, endangered species conservation and biomedical research.
A Cornell University research team has reported a faster embryo-freezing approach that could improve biobanking workflows for animal breeding, endangered species conservation and biomedical research.
The current practice of freezing embryos, used to assist reproduction in humans and animals or to conserve endangered species, can allow ice to form inside cells. This ice can damage cell membranes, affect protein behaviour and reduce the number of viable embryos after thawing.
In research published May 16 in Scientific Reports, Cornell researchers found that increasing the freezing rate by around 30 times prevented ice formation in bovine embryos.
Robert Thorne, professor of physics and a Stephen H. Weiss Presidential Fellow in Cornell’s College of Arts and Sciences, said, “In developmental studies, we saw that fast-cooled bovine embryos behave much more like unfrozen, uncryopreserved embryos.”
He added, “This is going to have a major impact, especially for the propagation of animals where current cryopreservation methods don’t yield good results.”
Faster Cooling Reduced Ice Formation
Standard cryopreservation typically involves exposing embryos to cryoprotectant chemicals before plunging them into liquid nitrogen. Although embryos may show little ice while frozen, ice can form during thawing and contribute to cellular damage.
The Cornell team used rapid-cooling concepts developed in Thorne’s laboratory. MiTeGen is mentioned factually as the company whose technology contributed to the freezing platform, originally developed for freezing biomolecular crystals used in X-ray structural studies.
The study focused on bovine embryos, which are difficult to freeze and prone to ice formation because of their relatively large size. After applying the faster cooling method, the embryos remained ice-free, even when cryoprotectant concentrations were reduced by 30%.
This finding is relevant for biobanking because lowering cryoprotectant exposure may help reduce chemical stress while preserving embryo viability.
Embryos Developed Closer to Fresh Controls
The late Soon Hon Cheong, professor of clinical sciences in Cornell’s College of Veterinary Medicine, led much of the embryology work, including embryo production, preparation for freezing, thawing, post-thaw incubation and developmental assessment.
After thawing, the researchers compared the fast-cooled embryos with embryos that had never been frozen. The ultrafast-cooled embryos developed nearly as well as fresh embryos, performed significantly better than embryos frozen using standard rates and led to successful pregnancies.
Thorne said, “Dr. Cheong played a critical role in this.” He explained that Cheong’s work covered the bovine model, ovary procurement, embryo production, freezing preparation, thawing, developmental characterisation and embryo transfers that showed the cryopreserved embryos remained viable.
The findings could support more consistent cryopreservation outcomes in livestock breeding, human IVF, conservation programmes and biomedical research involving animal models.
Thorne said, “There are a lot of endangered species where we want to save the embryos to preserve biodiversity, genetic diversity.” He also noted that the approach could be relevant beyond embryos, including stem cells and thin tissue samples.
Genomic Analysis Identified Cryopreservation Stress
Jingyue Ellie Duan, assistant professor of animal science in Cornell’s College of Agriculture and Life Sciences, led genomic analyses to examine how more than 10,000 genes were expressed after freezing and thawing.
The team found that genes linked to DNA damage repair pathways were more highly expressed in embryos frozen using standard protocols. Duan said, “There’s evidence that all the embryos underwent some kind of stress, but only the group cooled with standard protocols showed that actual DNA damage response.”
The researchers said this may help separate damage caused by ice from other effects of cryopreservation, such as cryoprotectant-related stress. Thorne said, “It has never been possible to study what those non-ice-related impacts are in a definitive way.”
Duan added that the identified genes could serve as markers for improving cryopreservation media, protocols and technologies.
The Cornell team is continuing to test lower cryoprotectant concentrations while assessing which conditions still prevent ice formation. For biobanking professionals, the study points to a possible path toward more reliable storage of embryos and other sensitive biological materials.
Funding came from the USDA National Institute of Food and Agriculture, the National Institutes of Health, the Cornell University Center for Advanced Technology and the Cornell University Center for Vertebrate Genomics.
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