Islets are clusters of cells within the pancreas containing the insulin-producing beta cells that are critically important in diabetes. This close-up image of an islet shows beta cells in green.
Breaking new ground
In February 2006 Hering, Sutherland, and colleagues at the University of Minnesota announced a major step forward in efforts to overcome the islet supply issue. In a paper published in the scientific journal Nature Medicine, the researchers reported they had reversed diabetes in monkeys using islets harvested from pigs.
"People thought it was impossible," Hering says. "This is really breaking new ground."
Xenotransplantation — or transplanting tissue from one species into another — generally causes a hyperacute rejection that is dramatically more severe than immune responses to transplants within a species. Hering and colleagues discovered that, unlike other pig tissue, most pig islets don't carry the protein that stimulates this hyperacute reaction. As a result, they were able to successfully implant the islets into monkeys using immunosuppression regimens similar to those used in human organ transplants. All 12 monkeys in the study produced enough insulin to control their blood sugar after the transplant. Although some of the monkeys had trouble with blood clots, islets were still functioning in some animals 100 days after the transplant.