In the ongoing search for a cure for baldness, scientists have found yet another biological clue in studying both mice and men.

Male pattern baldness comes from a combination of testosterone and genetics, a duo that leads hair follicles to shrink over time.

Researchers at the University of Pennsylvania studied men with male pattern baldness and found that bald areas of their scalps had higher levels of  a protein called  prostaglandin D2 than the hairier parts . When they applied the protein to human hair follicles in a lab dish, they found that the hair stopped growing.

Dr. George Cotsarelis, chairman of dermatology at the Perelman School of Medicine at U of Penn, said those findings may lead researchers to a treatment that could suppress prostaglandin D2 and the genes that make it to stop or even reverse hair loss.

The study wasn't the first to hint at a possible treatment for those who are shiny on top. Scores of researchers have identified factors linked to baldness, such as stem cells and stress, and potential hair-raising therapies.

But Cotsarelis said this studywas the first to study human scalps along with mice, meaning the findings apply directly to people, not just rodents.

"This is a much more targeted approach and much more likely to yield a treatment," Cotsarelis said.

Human and mouse hair follicles typically go through cycles of growth and regression. By studying mice, the researchers also found that the levels of the protein were highest right before the hair follicle entered its regression phase. Cotsarelis said a particularly high level of prostaglandin D2 might keep the follicle in the regressed phase, preventing hair from growing.

In a report published Wednesday in the journal Science Translational Medicine, the authors noted that there were several drugs currently being developed to combat male pattern baldness, and a number of these drugs targeted the prostaglandin pathway. Cotsarelis said assuming the drugs pass muster regarding safety and other regulatory hurdles, they could lead to a cream or medication for male pattern baldness.

Cotsarelis said he also hoped to research what the findings mean for women who lose their hair.

"We don't know whether women with hair loss have elevated levels of the protein in their scalp. That's something I'd like to find out as well," he said.