Birth of offspring derived from cryopreserved rat sperm after shipment in a Styrofoam box at −80°C

Archiving and sharing cryopreserved rat sperm can improve animal experiments' reliability, reproducibility, and sustainability in the scientific community. When sharing cryopreserved sperm from genetically engineered rats, a shipment system is required. Generally, a dry shipper, which can maintain at below -150°C, is the most widely used for sperm transport. However, using it for shipping cryopreserved sperm faces some difficulties, such as the risk of transporting hazardous materials (liquid nitrogen), its high cost, and the round-trip fee. Recently, the shipment of cryopreserved mouse sperm with dry ice at -79°C has been alternatively accepted in the scientific community. However, its outcome in terms of the fertilization and developmental abilities of the cryopreserved rat sperm was not examined. Therefore, this study aimed to examine the fertilization and developmental abilities of cryopreserved rat sperm after being stored in a deep freezer (-80°C) and dry ice (-79°C). We also demonstrated the transport of cryopreserved rat sperm in a Styrofoam box with dry ice. The fertilization rate of cryopreserved sperm stored in a deep freezer or dry ice was comparable to that in liquid nitrogen. In the transport experiment, the rat sperm transported between Kumamoto and Hokkaido maintained a high fertilization rate, and live pups were obtained from the embryos derived from the transported sperm. Fertilization and developmental abilities of cryopreserved rat sperm were maintained after shipment using a Styrofoam box with dry ice for storage.