Reproductive technologies in swine

Reproductive ability of minipigs as surrogates for somatic cell nuclear transfer

Pigs are genetically, anatomically, and physiologically similar to humans. Recently, pigs are in the spotlight as a suitable source animal for xenotransplantation. However, to use pigs as source animals, pigs should be raised in designated pathogen-free facilities. There is abundant data from embryo transfer (ET) experiments using farm pigs as surrogates, but data on ET experiments using minipigs are scarce. Eighty minipigs were used for ET experiments and after transplantation, the implantation and delivery rates were investigated. It was also confirmed whether the pregnancy rate could be increased by changing the condition or surgical method of the surrogate. In the case of minipigs that gave birth, the size of the fetal sac on the 28th day of ET was also measured. The factors that can affect the pregnancy rate such as estrus synchronization program, ovulation status at the time of ET, the number of repeated ET surgeries, and the ET sites, were changed, and the differences on the pregnancy rate were observed. However there were no significant differences in pregnancy rate in minipigs. The diameter of the implanted fetal sac on the 28th day after ET in the minipigs whose delivery was confirmed was calculated to be 4.7 ± 0.5 cm. In conclusion, there were no significant differences in pregnancy rate of minipigs in the comparative experiment on various factors affecting the pregnancy rate. However, additional experiments and analyses are needed due to the large individual differences of the minipigs.

Practical Approaches for Knock-Out Gene Editing in Pigs

Pigs are an important resource for meat production and serve as a model for human diseases. Due to their physiological and anatomical similarities to humans, these animals can recapitulate symptoms of human diseases, becoming an effective model for biomedical research. Although, in the past pig have not been widely used partially because of the difficulty in genetic modification; nowadays, with the new revolutionary technology of programmable nucleases, and fundamentally of the CRISPR-Cas9 systems, it is possible for the first time to precisely modify the porcine genome as never before. To this purpose, it is necessary to introduce the system into early stage zygotes or to edit cells followed by somatic cell nuclear transfer. In this review, several strategies for pig knock-out gene editing, using the CRISPR-Cas9 system, will be summarized, as well as genotyping methods and different delivery techniques to introduce these tools into the embryos. Finally, the best approaches to produce homogeneous, biallelic edited animals will be discussed.