Mouse pancreatic islets, grown inside rats and then transplanted into diabetic mice, can function normally for prolonged periods of time, a paper published online in Nature this week reveals. This proof-of-principle study demonstrates how the organs of one species can be grown inside the body of another, a method that could one day aid the production of transplantable human tissue, although many technical challenges and ethical and legal questions would first need to be addressed.
Hiromitsu Nakauchi and colleagues injected mouse pluripotent stem cells into embryonic rats that were unable to grow their own pancreas. After the stem cells had developed into islet cells, they were isolated and transplanted into diabetic mice where they successfully normalized and maintained blood glucose levels for over a year. No long-term immunosuppression (excluding the first 5 days after transplant) was needed.
When medication fails to stabilize the type I diabetic condition, in which insulin-producing cells are lost, pancreatic islet transplantation can offer hope to people with diabetes. Suitable donor tissue, however, can be hard to come by, a problem that is shared by the many thousands of patients waiting for transplants who suffer from other conditions. Pluripotent stem cells offer the potential to produce unlimited quantities of replacement cells and tissues, but the scenario outlined here would have to be modified for human application. Organs would need to be generated in animals that are close to humans both in size and evolutionary distance, such as sheep, pig or non-human primates, the authors say.