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Stem Cells Reverse Diabetes in Mice
  
By Nancy Touchette

Researchers have cured diabetes in mice by injecting bone marrow stem cells into the bloodstream. The stem cells seek out damaged tissue in the pancreas, where they appear to trigger the growth of new cells. If bone marrow stem cells have the same effect in humans with diabetes, they could be used to treat patients straightaway.


Nonobese diabetic mouse.

“This is a very significant study,” says Joel Habener of Harvard Medical School in Boston, who studies stem cells in the pancreas. “It suggests that there is something in the bone marrow that can stimulate the pancreatic stem cells to regenerate.”

It can take decades to bring a new drug to the marketplace. But bone marrow transplants have been used for years to treat a host of blood disorders, including leukemia and sickle cell disease. They have been proven safe and would require no government approval for use as a possible diabetes treatment in humans.

“There’s nothing to prevent people from trying this in humans,” says Habener. “People with diabetes have been waiting for a cure for years and years. Why not go ahead and try?”

Diabetes, which affects 150 million people worldwide, occurs when the pancreas does not produce enough insulin or when cells of the body become resistant to insulin. As a result, glucose accumulates in the bloodstream, leading to severe complications, including heart disease, nerve damage, stroke, blindness, and kidney failure.

In the new study, Mickie Bhatia and his colleagues at Robarts Research Institute in London, Ontario, first treated mice with a drug that destroys the pancreas and makes them diabetic. The diabetic mice had low levels of insulin and high levels of glucose in their blood.

But when the researchers injected the mice with bone marrow stem cells, the symptoms of diabetes reversed within 2 weeks. Insulin levels rose and blood glucose levels fell to near-normal values.

Labeling of the donor cells revealed that the new cell growth had come from cells already within the pancreas, not from the injected cells.


Bone marrow stem cells (green) induce the regeneration of insulin-producing islet cells of the pancreas (red) in mice. Scale bar, 50 micrometers.

“We almost didn’t believe the results ourselves,” says Bhatia. “We have had the results for a few years, but held back publishing them. But it’s a consistent robust effect.”

The researchers also found that the injected bone marrow cells triggered new growth only in damaged pancreatic tissue. In mice with intact pancreases, no regeneration occurred.

“Bone marrow cells only go to the pancreas if it’s injured,” says Bhatia. “Something at the injury site causes the stem cells to home in to the damaged pancreas. We have no idea what that could be.”

Other studies have shown recently that bone marrow stem cells can become different kinds of cells in the body, including heart, liver, pancreas, and nerve. But these findings have been controversial. Some experiments suggest that the stem cells can themselves be turned into different types of cells, while others suggest that the change occurs because the cells fuse to form hybrid cells.

Bhatia’s study is different because it suggests that the bone marrow stem cells do not themselves become pancreas cells. Instead, the cells somehow stimulate new growth in cells that are already in the pancreas.

Just how this occurs is not known, but Habener believes that bone marrow cells are secreting some kind of signal that tells stem cells in the pancreas to grow.

If researchers could isolate the substance that triggers the regeneration of pancreas cells to treat diabetes, it could be given directly to patients, thus avoiding transplants.

“We could just give a shot of this stem cell stimulator, and the pancreas could make new cells,” says Habener. “It would be a wonderful way to treat the disease.”

—Related Articles—

Bone Marrow Heals the Heart

Stem Cell Therapies: Time to Step Back or Forge Ahead?

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Hess, D. et al. Bone marrow-derived stem cells initiate pancreatic regeneration. Published online in Nature Biotechnology (June 22, 2003).
 

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