Wnt Proteins Act on Adult Stem Cells to Boost Regeneration

By Rose Hoban, Voice of America News, August 16, 2007

When we are young, our organs, bones, and muscles heal fairly quickly from injury. However, this process slows down as we age. When older, our recovery is also more limited and regeneration is not as strong compared to when we are young. When we are younger, we get a better build after injury as opposed to when we are older. The answer to why this is the case can be found on the cellular level according to researchers.

The process of cell injury and cellular aging is being studied by Professor Thomas Rando who is a professor of neurology at Stanford University. He has found that an important role in the healing process if played by adult stem cells. Adult stem cells allow a tissue to repair itself after injury says Rando.

"You cut your skin the skin heals itself. That's because there are stem cells sitting in skin that are continuously generating new skin cells," Rando says.

"Without these stem cells, you would run out of blood cells, you would run out of skin cells, you would run out of cells in your gut that are always turning over, and there are stem cells in a lot of other organs as well and tissues, like skeletal muscle, like liver, even some in the brain."

Wnt proteins, which are a cell product, were the focus of Rando's study. In response to tissue damage, cellular regeneration by stem cells is aided by the presence of the Wnt protein according to researchers. But that is not all they are limited to says Rando.

"What we found surprisingly was that with age it appears as if there are low levels of these Wnt proteins that are continuously acting on stem cells," Rando explains.

"And it's something about that continuous activity at a low level that instead of promoting stem cell function, they actually inhibit stem cell function. When the cells are exposed to this environment where there's a lot of this Wnt protein around, they essentially go into a dormant state or a state that is more difficult to get them to begin dividing and making new healthy cells."

If researchers could find ways to enhance tissue repair by blocking the Wnt protein signals, new therapies could be developed. The effects of Wnt need to be better understood to make this a reality.

"It's really more in the realm of… if in an older person there is an injury to a tissue, whether it's a skin wound or a broken bone or a muscle injury, can we enhance the repair process?" Rando speculates. "Not to make the old person young but to make the old tissue repair as well as young tissue repairs."

A recent issue of the journal Science has published his research. In order to better understand how the function, Rando continues to study the Wnt proteins.