Tackling diabetes by using rats with mouse-pancreas transplanted into them is discussed in a new study published in Nature. These findings might, one day, pave the way to a similar transplant in humans.
Mice & Rats & Diabetes
Diabetes is characterised by a pancreatic functional impairment. The pancreas is the organ meant to secrete the hormone insulin that is responsible for the assimilation of glucose into body cells; however, that of diabetic patients does not function properly, leading to abnormal blood glucose levels. The new study shows how this can be solved, providing hope for humans, as it entails an interspecies transplant: researchers from the Stanford University School of Medicine and the Institute of Medical Science at the University of Tokyo came together to grow pancreases obtained from mice in rats.
Mouse Pancreatic Cells Transplanted Into Rat Embryos
The team of scientists inserted pluripotent stem cells (cells which can develop into any type of specialised cell) obtained from mice into rat embryos. The mouse cells were inserted into rat embryos, and not into rats that were already born, because the embryos would not have yet developed immune tolerance. So, the rat embryos were made to recognise the mouse tissues as their own, and did not later reject them; also, they were previously genetically engineered to grow no pancreas of their own, and so the rats had to depend on the mouse cells to have a pancreas. They were still subjected to immunosuppressive therapy for a few days to prevent rejection of the foreign organ.
From Mice to Rats to Mice Again
The rats were born, and allowed to grow. Thereafter, the scientists took insulin-secreting cells from their pancreases, and transferred them into diabetic mice. The transplanted cells were not rejected because the stem cells used to grow the pancreas were genetically compatible with the recipient mice.
The results show that the mice eventually had normal blood glucose levels after the operation.
“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,” says senior author of the paper, Hiromitsu Nakauchi. “Furthermore, the recipient animals only needed treatment with immunosuppressive drugs for five days after transplantation, rather than the ongoing immunosuppression that would be needed for unmatched organs.”
Long-Term Good Results
The pancreatic cells from the mice were then examined 10 months after the transplant. The observations of the researchers show that the interspecies intervention was indeed effective.
“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.”
Interspecies Transplant: Hope for Diabetic Humans
The findings are particularly positive for humans because the possibility of an interspecies organ transplant seems less out of reach. Perhaps, one day, researchers will have figured out how to grow human pancreatic cells inside animals to be later transplanted into diabetic humans.
Harvesting human organs from large animals that would be genetically matched could help those waiting for organs transplants; furthermore, lifelong immunosuppression would not be a problem either.
It is to be noted that much more research needs to be done before this is executed in humans. On top of the scientific work awaiting researchers, the the ethics of the matter also have to be considered: can human stem cells be inserted into animal embryos from which specialised cells are transplanted into humans?