Successful induction of pseudopregnancy using sonic vibration in mice.

Embryo transfer (ET) is an essential reproductive technology for the production of new animal strains and maintenance of genetic resources. We developed a method, named Easy-ET, to induce pseudopregnancy in female rats by artificial stimulation using sonic vibration instead of mating with vasectomized males. This study examined the application of this method for the induction of pseudopregnancy in mice. Offspring were obtained from two-cell embryos transferred into females with pseudopregnancy induced using sonic vibration in proestrus on the day before embryo transfer. Furthermore, high developmental rates of offspring were observed when pronuclear and two-cell embryos were transferred to females in estrus that were stimulated on the day of embryo transfer. Genome-edited mice were also obtained using frozen-warmed pronuclear embryos with clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated system (Cas) nucleases introduced using the technique for animal knockout system by electroporation (TAKE) method, which were transferred to females with pseudopregnancy induced on the day of embryo transfer. This study demonstrated that induction of pseudopregnancy by sonic vibration was also possible in mice.

Successful pseudopregnancy of rats by short period artificial stimulation using sonic vibration.

Psuedopregnancy for embryo transfer (ET) is usually induced in rats by mating with vasectomized males. Previously, we successfully induced pseudopregnancy using sonic vibration instead (Easy-ET method). The transferred embryos developed normally. Conventionally, stimulation is performed 7 × 30 s with 5 min intervals at the day before ET. However, this protocol is time-consuming because it imitates natural mating behavior. Here, we investigated pseudopregnancy induction with shorter stimulation times. Stimulation was performed 2 × 30 s, with 30 s intervals at the proestrus stage at the day before ET. Of the transferred pronuclear or two-cell embryos, 43% or 62% developed normally, respectively. Furthermore, 67% or 68% of transferred pronuclear or two-cell embryos in rats at estrus stage stimulated on the day of ET developed normally, respectively. Pseudopregnancy was successfully induced with shorter stimulation. Furthermore, this protocol may be used to perform a single-day stimulation and ET operation at the estrus stage.

Simple induction of pseudopregnancy by artificial stimulation using a sonic vibration in rats.

Embryo transfer has been used as one of the essential reproductive technologies for production of new strains and maintenance of genetic resources in animals. Mating with vasectomised male rats is a requirement for inducing pseudopregnancy in female rats selected for embryo transfer. Although this procedure has been used routinely, large breeding space and high expenditure are required to maintain a sufficient number of females and vasectomised males. This study was performed to induce pseudopregnancy in females by artificial stimulation using sonic vibration instead of vasectomised males. The females continued to be in the dioestrus stage for at least 14 days after artificial stimulation was performed. Of fresh 2-cell embryos that transferred into the oviducts of females after artificial stimulation, 56% was implanted and 50% was developed to offspring. Approximately 46% of the frozen 2-cell embryos were implanted and 24% developed into offspring. Furthermore, 66% of the fresh pronuclear embryos were implanted and 60% developed into offspring. This study successfully induced pseudopregnancy in rat females by artificial stimulation using a sonic vibration. This method, 'Easy-ET', was useful for efficient production and maintenance of rat strains.