Photo/IllutrationA pig whose immune system is partially inhibited (Provided by Nature Communications)

Japanese researchers developed a special pig whose body could be used to grow human internal organs for future transplants.

Eiji Kobayashi, a specially appointed professor of regenerative medicine at Keio University, and other scientists removed organs that produce immune cells from the pig’s body so that it would not reject the human organs as foreign substances.

The breakthrough was published in the British scientific journal Nature Communications on May 21.

Since swine’s organs are as large as those of humans, scientists have been trying to graft human organs in pig bodies using induced pluripotent stem (iPS) cells.

One big problem in previous efforts was that the pigs’ immune cells attacked the human organs as alien substances.

However, halting all functions of the pig’s immune system through gene manipulation left it vulnerable to infection by viruses and other pathogens. The challenge was how to protect such pigs from infectious diseases to extend their short life.

Kobayashi and his colleagues surgically removed the pig’s thymus gland and spleen, which produce T cells and B cells that attack the human organs. Drugs were also used to inhibit the activity of other immune cells remaining in its body.

The researchers transplanted artificial blood vessels derived from human cells into the pig. The grafts were not rejected and vascular tissue was regenerated.

The pig, which was kept under conditions containing germs, lived for more than five months, according to the scientists.

“We succeeded in creating a pig that is not easily affected by pathogens but does not reject human-derived cells by not suppressing all functions of its immune system,” Kobayashi said.