Pity the pancreas. Although researchers appear to have found the stem cells that give rise to--and potentially could be used to rejuvenate--many other parts of the body, pancreatic stem cells have been remarkably elusive. Now, however, a team has identified cells in mice that can become a variety of pancreatic cell types, including those that make insulin. The discovery may be a step toward a long-sought cure for diabetes.
People with type I diabetes can't make insulin, the hormone that regulates the amount of sugar coursing through the blood. That's because the insulin-making cells in the pancreas, called b cells, are either missing or malfunctioning. Because b cells are extremely hard to culture, the only source for transplants is cadavers. Pancreatic stem cells that continuously crank out b cells would be a more plentiful alternative, but researchers hit a snag earlier this year when Douglas Melton and colleagues at Harvard University showed that b cells in adult mice actually arose from other b cells, not from stem cells (5 May, ScienceNOW).
Refusing to give up the search, another team of researchers at the University of Toronto led by Derek van der Kooy looked for stem cells in pancreatic cells from adult mice. To boost their odds, the researchers bathed the cells in culture media that encourage growth of neural stem cells. About one out of every 5000 cells quickly multiplied into a group of cells, a characteristic of stem cells not shared by typical adult cells.
The team found another hallmark of stem cells: The cells were poised to become different kinds of tissue. When the team changed the medium to encourage the cells to differentiate, neurons arose from the mix, as did a variety of pancreatic cells, including b cells, based on the cells' genetic profiles. The b cells secreted insulin, the team found, and adding sugar to their media made the b cells spew out more than twice as much of the hormone, just as b cells in the body release insulin in response to sugar. They reported their findings online 22 August in Nature Biotechnology.
The team hasn't proved that the new cells are truly stem cells, says Harvard developmental biologist Yuval Dor, a co-author on Melton's paper. "Nevertheless, the work is an important breakthrough because it can be useful for therapy," Dor adds. As long as the technique produces enough b cells to combat diabetes, he says, it doesn't matter how the cells arise.