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Researchers Study Blood Vessel Stem Cells

Scientists around the world are learning more about stem cells and how they function to help the body restore itself throughout the lifespan.

Stem cells exist in all sorts of tissues throughout the body – they help the body to continuously repair itself. And with the right stimulus, they can develop into many different kinds of cells.

Researchers Keith March at Indiana University in Indianapolis recently learned more about one kind of stem cell – it exists on the outer lining of blood vessels. He explains that blood vessels have an inner lining which are called the endothelial cells, and they have an outer lining which contain these stem cells.

So we wondered whether those stem cells that were in the position of the outer wall of the blood vessel were being, March says. And we started experiments to test that question.

March and his colleagues found that the two kinds of cells were indeed interacting. It turns out that the stem cells had the ability to keep the epithelial cells strong – as long as endothelial cells sent the right signals.

But if the endothelial cells were diseased or damaged – for example, from high blood pressure, high cholesterol or high blood sugar – stem cells on the exterior walls of blood vessels transformed themselves into fat cells.

And one of the things we think could happen is that as one gets these various diseases, the endothelial cell actually becomes unhealthy, at the lining of the blood vessel wall, March says. And as a result of that unhealthiness, it's no longer able to restrain the stem cell from actually turning into a fat cell.

So in effect, March explains, the longer a person stays healthy, the less likely he or she is to develop fat cells and become obese. But if blood vessels start to become unhealthy, it starts a cycle of increasing fat, which makes the blood vessels more diseased, which in turn creates more fat cells. He describes it as a viscious cycle.

We see that there are signaling mechanisms that help to keep the fat stem cells from turning into fat…as they turn into fat, or begin that process, those signaling mechanisms are actually lost, March says. So it's almost like when you turn off the switch, that keeps it from becoming a fat cell, the switches actually disappear from the wall.

March says he and his colleagues are pursuing more research into these stem cells that line blood vessels. He says that if they can learn more about how they become fat cells, they might be a target for a drug that can help arrest the process of becoming obese.

March's research is published in the journal Stem Cells.