Stem Cells Finally Found in Pancreas
THURSDAY Jan. 24, 2008 -- An international team of researchers has finally managed to locate stem cells in the pancreas -- in mice, at least.
If the findings are confirmed in humans, they could pave the way for dramatic new therapies for diabetes, namely the regeneration of beta cells so the body could once again produce its own insulin. Until now, scientists had all but abandoned hopes that the pancreas made its own stem cells because they had failed to find evidence to support the theory.
But any clinical advances from the new research are still a long way off, experts cautioned.
"This is the first conclusive evidence that there are stem cells in the pancreas, but any potential benefit is a very long way away," said Juan Dominguez-Bendala, director of Stem Cell Development for Translational Research at the Diabetes Research Institute of the University of Miami Miller School of Medicine.
"If this kind of cell and their progenitors with a capacity to divide exist in the pancreas of man, and if we can identify the factors that are responsible to induce their proliferation and differentiation, then these latter processes might be stimulated in vitro but also, by noninvasive means, in vivo," said senior study author Harry Heimberg, an associate professor at the Diabetes Research Center of Vrije Universiteit Brussel in Belgium.
The findings are published in the Jan. 25 issue of the journal Cell.
Diabetes is primarily a failing of the pancreatic beta cells to produce insulin. Beta cells are one of several types of cells making up clusters of cells called the islets of Langerhans.
Insulin is a hormone that moves blood sugar from the bloodstream to the cells, where it is used as energy.
In type 1 diabetes, the pancreas has lost all or virtually all of its ability to produce insulin. In type 2 diabetes, the loss of beta cells is more gradual.
Islet-cell transplantation, in which islets are transferred from one person to another, is performed today but is limited in scope because of a shortage of donors, according to the study.
The very existence of pancreatic stem cells is controversial. A recent study out of Harvard found that the major source of new beta cells in adult mice was preexisting beta cells, not stem cells. The finding reduced the urgency to track down pancreatic stem cells.
"If stem cells didn't contribute, what was the point," said Dominguez-Bendala.
For this study, Heimberg and his colleagues cut off the duct that drains digestive enzymes from the pancreas in mice. Within two weeks, the number of beta cells in the pancreas doubled.
Not only did the number of beta cells increase, the mice started producing more insulin.
"When damaged a specific way, it triggered stem cells" production, Dominguez-Bendala said.
The newly identified stem cells were almost identical to embryonic beta cell progenitors. In fact, the gene Neurogenin 3 (Ngn3), which plays a role in embryonic development of the pancreas, is also involved in the formation of these new beta cells, the researchers said.
"This is a model of regeneration no one has tested before," Dominguez-Bendala said. "From a basic science point of view, it's very exciting. It opens the door to potential therapies. If we could trigger regeneration, that would be fantastic."
"This demonstrates a stem cell repair mechanism in the pancreas that, if we understand it more, then we can help develop more cures with either transplantation or with drugs that can increase the body's own stem cells and beta cells," said Paul Sanberg, director of the University of South Florida Center for Aging and Brain Repair in Tampa.
For more on pancreatic islet transplantation, visit the U.S. National Diabetes Information Clearinghouse.
Posted: January 2008
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