Embryo Development and Cryopreservation in Porcine Systems

Porcine embryogenesis begins with fertilisation, followed by successive mitotic divisions that transform the zygote into a morula by day 4 and a blastocyst by day 6 post-insemination. At the blastocyst stage, coordinated interactions between the inner cell mass and the trophectoderm underpin implantation potential and foetal viability. Cryopreservation, and in particular vitrification, enables long-term storage and dissemination of valuable genetic lines, supports biomedical models and underpins genetic resource banks. Vitrification achieves ultra-rapid cooling to a glass-like state, minimising ice crystal formation, but introduces osmotic and thermal stresses that can perturb membrane integrity, metabolic pathways and gene expression. Recent efforts have focused on optimising cryoprotective agents, culture media and devices to improve post-warming survival and in vivo developmental rates. Alternative storage methods, such as liquid preservation at ambient or sub-physiological temperatures, have been explored to simplify logistics and comply with transport regulations. Advances in transcriptomic and epigenetic profiling now provide insight into the molecular signatures of cryodamage and repair, informing the refinement of protocols. Non-surgical embryo transfer techniques and defined systems for high-throughput vitrification promise to expand the practical use of embryo technologies in swine breeding, biomedical research and conservation, highlighting the global significance of robust porcine cryobiology.

Research from Nature Portfolio

One study introduced a pH-stable, chemically defined medium for porcine embryo vitrification and warming, replacing conventional gas-equilibrated solutions. This approach yielded over 90% post-warming survival and maintained farrowing rates above 70%, demonstrating that buffer stability enhances field-applicability and standardisation of cryopreservation workflows. Another investigation compared non-surgical deep uterine transfer with the traditional surgical method using vitrified morulae and blastocysts. It was shown that transferring a higher number of embryos via a minimally invasive approach equalises farrowing rates and litter sizes to those achieved with surgery, offering a welfare-improved route for widespread embryo transfer in pigs. A further report explored liquid preservation of morulae and blastocysts at 20 °C in a protein-supplemented medium, revealing that embryos can remain unhatched yet viable for up to 72 hours, thus providing an alternative to vitrification for embryo transport under restrictive conditions.

Embryo Development and Cryopreservation in Porcine Systems publication trend

The graph below shows the total number of articles in embryo development and cryopreservation in porcine systems across all publications each year (not limited to Nature Index journals).

Technical terms

Vitrification: Ultra-rapid freezing technique that solidifies biological samples into a glass-like state without ice crystal formation.

Cryoprotective agent: Substance (e.g., ethylene glycol, glycerol) that safeguards cells from ice damage during freezing and thawing.

Morula: Early multicellular embryonic stage characterised by a compact mass of blastomeres before blastocoel formation.

Blastocyst: Embryonic stage comprising a fluid-filled cavity (blastocoel), an inner cell mass and surrounding trophectoderm.

Embryo transfer: Placement of embryos into the uterus of a recipient to achieve pregnancy, which may be surgical or non-surgical.

References

1. Unveiling how vitrification affects the porcine blastocyst: clues from a transcriptomic study. Journal of Animal Science and Biotechnology (2022).
2. Nonsurgical deep uterine transfer of vitrified, in vivo-derived, porcine embryos is as effective as the default surgical approach. Scientific Reports (2015).
3. Effective vitrification and warming of porcine embryos using a pH-stable, chemically defined medium. Scientific Reports (2016).
4. Prevention of hatching of porcine morulae and blastocysts by liquid storage at 20 °C. Scientific Reports (2019).
5. The Open Cryotop System Is Effective for the Simultaneous Vitrification of a Large Number of Porcine Embryos at Different Developmental Stages. Frontiers in Veterinary Science (2022).