Freezing the Future: A Breakthrough in Chicken Genetic Preservation

Scientists have made a significant step forward in preserving chicken genetic resources. This is crucial for both commercial breeds that supply eggs and meat globally and for conserving indigenous breeds. The goal is to manage breeding effectively according to future demands. Chicken embryos are tricky to cryopreserve because they are attached to a large yolk. As a result, researchers have turned their attention to primordial germ cells, or PGCs, which are the embryonic precursor cells of gametes.

Cryopreserving PGCs is a novel strategy for maintaining chicken genetic resources without needing to breed live birds. Traditional cryomedia used for PGCs contain dimethyl sulfoxide or propylene glycol, along with serum. However, serum composition can vary greatly, leading to performance differences between lots. This inconsistency has sparked a demand for serum-free cryomedia with known compositions. Researchers have been exploring alternatives to serum, such as ovalbumin and sericin, to develop effective cryomedia.

Two new cryomedia have been developed: PO, which includes 7.5% propylene glycol and 5% ovalbumin, and PS, which includes 7.5% propylene glycol and 2% sericin. After PGCs were cryopreserved in these solutions, their viability and cell doubling times returned to normal levels comparable to those of unfrozen cells. Specifically, viability recovered within 6 days, and cell doubling times returned to normal within 2 days post-culture.

When these frozen-thawed PGCs were transplanted, their ability to migrate to the gonads was initially lower but recovered to normal levels after 4 days of culture. A significant breakthrough came when viable offspring were successfully revived from a breed designated as a natural monument in Japan. These offspring came from PGCs that had been cryopreserved in the new serum-free cryomedia.

The development of these serum-free cryomedia marks a major advancement. They achieved over 60% recovery of viable PGCs after thawing, while also maintaining the cells' ability to contribute to the germline. This innovation could play a key role in the preservation of chicken genetic resources, supporting both commercial and indigenous breeds for future generations.