Useful short-range transport of mouse embryos by means of a nonfreezing technique

The survival of mouse morulae to be implanted on the uterine wall of a recipient after storage at 0 degree C in sucrose-containing medium has shown tendencies similar to those of blastocysts developing in vitro. The pregnancy rate, as defined by implantation sites per embryos transferred, has varied from 52.9 to 77.2% and decreased depending on the duration of storage (0 to 72 h), and was lower than the rate of blastocyst formation in vitro (57.2 to 87.3%). Regarding the birth rate, 56.0 to 59.4% of implanted embryos were delivered as live pups regardless of storage duration, with the exception of controls (78.9%, 0 h). Eventually, 37.0, 32.8, or 29.9% of embryos were obtained as live pups when preserved by our system for 24, 48, or 72 hours, respectively. This viable, highly reproducible nonfreezing technique is useful for embryo preservation. Embryos were transported to evaluate the efficacy of the nonfreezing method. Mouse morulae were kept in a thermos bottle filled with ice-water and packaged in polystyrene foam. The package was transported from Kochi to Sapporo, about 1300 km, within 48 hours during which it was possible to maintain 0 degree C in the bottle and deliver to most areas in Japan. After shipping, the survival of embryos was 46.8% for development to blastocysts in vitro, and 37.1% for the pregnancy rate, with a final birth rate of 14.1%. Transport factors other than storage may have contributed to the lower birth rate; however, our system is cheaper, more convenient, and more practical than others for short-range transport.