Looking good. The pancreas of a mouse after it was transplanted with human beta cells (left) looks similar to that of an animal that produces insulin normally (right).

Beta Cells Forever?

A major goal in the fight against type 1 diabetes is an adequate supply of insulin-producing cells. Now, a team of scientists in the United States and Japan have created a source of such cells in the lab, but it's not yet clear whether they'll be safe to transplant.

In type 1 diabetes, also known as juvenile diabetes or insulin-dependent diabetes, the body attacks and destroys the pancreas's insulin-producing beta cells. As a result, patients can't maintain safe glucose levels. One of the best potential cures may be giving patients new beta cells. But current efforts to do so are hampered in part by scarce supplies; for now, the cells can come only from cadavers. Some scientists have also turned to embryonic stem cells as a possible starting point for endless numbers of beta cells. Chicago Medical School immunologist and cell biologist Ji-Won Yoon tried another approach that had already proved successful in liver cells.

With his colleagues Michiki Narushima and Naoya Kobayashi, both surgeons at Okayama University Graduate School of Medicine and Dentistry in Japan, and others, Yoon began with human beta cells from cadavers. To expand this pool, his team inserted two genes into the cells that would "immortalize" them, allowing them to divide forever. Once they had a large number of insulin-producing cells, the researchers used a virus to remove the genes, which can also contribute to cancer. They then transplanted the cells into 10 mice that lacked beta cells, they report online 25 September in Nature Biotechnology. Forty weeks later, the mice "are still alive [and] very healthy," says Yoon. Control animals lacking beta cells died within 2 months.

Until now, "no one has been able to achieve the dual goal" of significant beta cell expansion while retaining the cells' function, says Christopher Newgard, a pancreatic islet biologist at Duke University Medical Center in Durham, North Carolina. The cells might be useful for lab-based beta cell experiments, but it's not clear they're safe for humans. "There is still uncertainty" over whether the cells might be cancer-inducing, says Nadya Lumelsky, an islet biologist at the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Maryland. Yoon agrees that much more testing is necessary before human transplants can be considered.

Related sites
The paper
Ji-Won Yoon's home page
Juvenile Diabetes Research Foundation