The achievement marks progress toward the team's goal of creating human pancreases in pigs for transplantation into human diabetics, the team, led by Hiromitsu Nakauchi, a professor at the University of Tokyo's Institute of Medical Science, said.
The team used male white pig embryos that had been genetically modified to lose their ability to grow their own pancreases, Japan Times reported.
The team, including Meiji University professor Hiroshi Nagashima, injected cells of normal female black pig embryos into the white pig embryos to create chimera blastocysts, which were then put into the wombs of other pigs. They gave birth to male white pigs with black pig pancreases.
In 2010, Nakauchi and his colleagues announced they created pancreases of rats inside mice.
Creating human pancreases in pigs by injecting human induced pluripotent stem cells into pancreas-deficient pig embryos is technologically difficult.
In addition, it would be ethically problematic if pigs carry to term embryos injected with human iPS cells, creating chimeras made up of both human and pig cells.
The findings are published online by the US journal Proceedings of the National Academy of Sciences.