In news that offers hope to millions of chrome-domes everywhere - yours truly included - Yale researchers have made a discovery that could lead to new treatments for baldness. While men with male pattern baldness still have stem cells in follicle roots, they need signals from within the skin to grow hair. Until now, the source of those signals that trigger hair growth has been unclear, but the Yale researchers claim to have now discovered it.

When hair dies, the researcher team led by Valerie Horsley, assistant professor of molecular, cellular and developmental biology, observed that the layer of fat in the scalp that comprises most of the skin's thickness shrinks. When hair growth begins, the fat layer expands in a process called adipogenesis. They identified a type of stem cell - adipose precursor cells - within the skin's fatty layer that is involved in the creation of new fat cells. They showed that these cells' production of molecules called PGDF (platelet derived growth factors), was necessary to spur hair regrowth in mice.

Horsley's team is trying to identify other signals produced by adipose precursor stem cells that may play a role in regulating hair growth. She also wants to know whether these same signals are required for human hair growth.

"If we can get these fat cells in the skin to talk to the dormant stem cells at the base of hair follicles, we might be able to get hair to grow again," said Horsley.

The Yale team's research is published in the September 2 issue of the journal Cell.