Scientists Grow Mouse Organs Inside Rats, Then Transplant Them Into Mice

Tomoyuki Yamaguchi
Tomoyuki Yamaguchi / Tomoyuki Yamaguchi

Researchers from Stanford University and the University of Tokyo have pioneered a technique to grow organs from one species inside another, then transplant them back into individuals of the first species. The technique, described this week in the journal Nature, suggests that we might someday be able to grow desperately needed human organs inside other animals.

The field of organ transplantation is no stranger to interspecies interactions. Surgeons have been giving patients heart valves from pigs for decades—a situation that speaks to the fundamental shortage of viable human organs available today. Researchers are currently attacking that issue from a number of different angles, including recycling used organs and 3-D printing new ones.

The latest study focused on the pancreas, an organ essential for digestion and regulating blood sugar. Pancreas transplants are very effective in combating Type 1 diabetes, but as with hearts and lungs, there just are not enough organs to go around.

To see if they could grow new, viable pancreata from scratch, researchers bred a type of rat that could not grow its own pancreas. They then implanted mouse stem cells into the rats while they were still embryos. The stem cells took, and grew successfully into mouse pancreatic cells. Next, the scientists removed these cells and transplanted them into diabetic mice.

Yamaguchi et al. in Nature

The new organs worked beautifully, as though the mice had grown them themselves, co-author Hiromitsu Nakauchi said in a statement: “We found that the diabetic mice were able to normalize their blood glucose levels for over a year after the transplantation of as few as 100 of these islets.”

Rejection of new organs is a substantial risk with any transplant, but the mice’s new pancreata made themselves right at home. The mice only needed a five-day course of immunosuppressive drugs to keep their bodies from attacking the new organs, as opposed to having to take those drugs for the rest of their lives.

“We examined them closely for the presence of any rat cells, but we found that the mouse’s immune system had eliminated them,” said Nakauchi. “This is very promising for our hope to transplant human organs grown in animals because it suggests that any contaminating animal cells could be eliminated by the patient’s immune system after transplant."

Further research and ethical discussions will be required before the technique can be used in other animals.