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Interspecies Transplant Paves the Way for Diabetes Therapy

  • Jessica Berman

Researchers have come closer to the “Holy Grail” of treatment for people with type 1 diabetes. They have successfully transplanted insulin-producing islet cells from one species into another without the use of immunity-suppressing drugs. In the future this could provide an unlimited supply of tissue to treat people whose bodies cannot produce insulin.

Insulin is a hormone produced by the pancreas that delivers glucose - a form of sugar that the body uses for fuel - to cells for energy. Since the immune systems of people with type 1 diabetes attack and destroy the islet cells that produce insulin, many sufferers must inject themselves with insulin frequently, simply in order to survive.

It has long been a goal of scientists to transplant islets into humans - from other humans or pigs - without their bodies rejecting them. Human cadaver transplants are difficult, while animal-to-human transplants have proved nearly impossible.

Now, investigators at Northwestern University in Illinois have carried out a successful interspecies islet cell transplant, from rats into mice, without the lifelong use of anti-rejection medications, which carry significant side effects and risks, including cancer.

The study's lead author, Xunrong Luo, head of the Northwestern medical school's human islet cell transplantation program, said the transplanted rat cells produced insulin in the mice for more than 300 days.

“They survived essentially indefinitely. So they continued to produce insulin without the need of any immunosuppression and [the cells] just continued to maintain normal glucose levels in these diabetic mice,” she said.

The mice were prepared for transplant by taking white blood cells from a rat’s spleen, which is part of the immune system, and bathing them in chemicals that put the cells into a sleeping state known as programmed cell death.

The altered cells were injected into mice. They entered the rodents’ spleen and liver but were soon mopped up [gathered, and destroyed ] by scavenger cells called macrophages, which recognized the sleeping rat cells as waste. In that process, fragments of the rat spleen cells wound up on the surface of the macrophages. This "trained" [conditioned] the mouse's immune-system T cells to accept islet cells, which researchers successfully transplanted seven days later.

“So we are pretty excited about that, because our next step is to see if we can translate this into [a] larger step, into larger animals,” she said.

Luo says her team now will try to transplant pig cells into monkeys. Her ultimate goal is to be able to tap into an unlimited supply of pig islet cells for transplants into people with type 1 diabetes.

An article on interspecies transplants of insulin-producing islet cells appears in the journal Diabetes.