Preservation of common carp germ cells under hypothermic conditions: Whole tissue vs isolated cells

The aim of this study was to optimize the conditions for hypothermic storage of spermatogonial stem cells (SSCs) and oogonial stem cells (OSCs) of common carp Cyprinus carpio. This was conducted by storing gonadal tissue or isolated cells for 24 hr under hypothermic conditions in the first experiment and by testing two different storage media (L-15 or DMEM supplemented with 10% FBS and 25 mM HEPES) and regular medium change (every 4 days) during two weeks of hypothermic storage in the second experiment. During the first 24 hr, isolated cells showed no decrease in viability, while cells obtained from hypothermically stored tissues displayed significantly lower viability after only 6 hr (Tukey's HSD, p < 0.01) indicating that hypothermic storage of isolated cells is superior to storing tissue pieces. The 2-week trial demonstrated that storage media have a profound influence, while regular medium exchange does not have a positive effect on cell viability. Viability of SSCs and OSCs after two weeks was approximately 40% and 25%, respectively; however, survival of ~70% was obtained after 10 days of storage for SSCs and 7 days for OSCs. Hypothermic storage developed in this study has many practical applications during the development of surrogate broodstock technologies for common carp, but also in carp hatcheries and for the conservation of genetic resources of closely related cyprinid species.