• Primordial germ cells (PGCs) are embryonic precursor cells for ova and sperm.
• We developed cryomedia that achieved higher post-thaw recovery of viable PGCs than existing cryomedia.
• We successfully revived the offspring of Kurokashiwa, a Japanese natural monument, with cryopreserved PGCs.

The conservation of chicken genetic resources is crucially important in the maintenance of economically valuable breeds for the sustainable production of eggs and meat. However, the cryopreservation of avian fertilized eggs is technically impossible because of their large yolk mass. At present, chicken genetic resources are maintained by breeding living birds. However, conservation of living chickens always carries the risk of loss owing to unexpected outbreaks of highly pathogenic avian influenza. As an alternative, primordial germ cells (PGCs), the first germ cell population established during early development, are the best candidates for the cryobanking of chicken germplasm. Chicken PGCs can be differentiated into functional ova and sperm following transplantation even after cryopreservation. Here, we developed cryopreservation media suitable for freezing chicken PGCs.

Here, we investigated the cryoprotective effects of propylene glycol (PG), one of the dihydric alcohols, on chicken PGCs. We found that the addition of trehalose, one of the disaccharides, and chicken serum to PG cryomedia potentiate the cryoprotective effects on chicken PGCs. Based on these findings, we designed cryomedia that achieved > 60% recovery of viable PGCs after thawing. Finally, we demonstrated the applicability of cryomedia in the cryobanking of PGCs from the rare chicken breed Kurokashiwa, a Japanese natural monument. We successfully revived the offspring of Kurokashiwa with cryopreserved PGCs.

The cryomedia developed in this study offers a more reliable and inexpensive protocol for the long-term cryopreservation of chicken PGCs. The prospective application of these cryomedia for cell-based cryobanking will contribute to the preservation of chicken genetic diversity for sustainability and adaptation to future poultry demands.

• Journal: Journal of Reproduction and Development
• Title: Development of cryopreservation media for the slow-freezing of cultured primordial germ cells in chicken
• Authors: Natsuko Hamai, Chihiro Koide, Yuki Tansho, Yukino Ooka, Mayo Hirano, Effrosyni Fatira, Masaoki Tsudzuki, Yoshiaki Nakamura
• DOI: 10.1262/jrd.2022-123 DOI