Stem cells not required.

The pancreas doesn't include stem cells that become insulin producers. Instead, the cells that make the hormone proliferate by dividing, researchers have discovered. The finding could have implications for future diabetes treatments.

Many of the body's tissues harbor caches of so-called adult stem cells that act like factories, churning out fresh cells to replace old ones. Some scientists had speculated that pancreatic stem cells exist, and that they might provide new treatments for diabetes. The new research suggests that scientists should instead search for ways to encourage insulin-producing cells, called beta cells, to divide more rapidly, says Jake Kushner, lead scientist for the study at the Children's Hospital of Philadelphia.

By feeding healthy mice a component of DNA modified to glow either red or green, Kushner's group could see beta cells once they formed in the animals. The team alternated the color every few weeks. Stem cells would go through several rounds of division in order to become beta cells, and so would incorporate both colors. Beta cells would divide only rarely and take on one color or the other, which is what the researchers saw.

"In every case, the beta cells were self-renewing, and there wasn't even a tiny contribution by cells that were undergoing more than one round of cell division; Kushner says. This result shows that active stem cells weren't present, the researchers report in the May 8 Developmental Cell.