Generation of insulin-like growth factor 1 receptor-knockout pigs as a potential system for interspecies organogenesis

Background: To overcome organ shortage during transplantation, interspecies organ generation via blastocyst complementation has been proposed, although not yet in evolutionarily distant species. To establish high levels of chimerism, low chimerism is required early in development, followed by high chimerism, to effectively complement the organ niche. Very few human cells are expected to contribute to chimerism in heterologous animals. Previous studies had demonstrated increased donor chimerism in both intra- and interspecies chimeras in rodents, using insulin-like growth factor 1 receptor (Igf1r) knockout (KO) mice; deletion of the Igf1r gene in the mouse host embryo created a cell-competitive niche. The current study aimed to generate IGF1R-KO pigs and evaluate whether they have the same phenotype as Igf1r-KO mice.

Methods: To generate IGF1R-KO pigs, genome-editing molecules were injected into the cytoplasm of pig zygotes. The fetuses were evaluated at 104 days of gestation.

Results: IGF1R-KO pigs were generated successfully. Their phenotypes were almost identical to those of Igf1r-KO mice, including small lungs and enlarged endodermal organs in fetuses, and they were highly reproducible.

Conclusions: Pigs may allow the generation of organs using blastocyst complementation with developmentally-compatible xenogeneic pluripotent stem cells over a large evolutionary distance.