WEDNESDAY, March 21 (HealthDay News) -- Men worried about encroaching baldness, take heart: A genetic analysis of tissue taken from both bald and hairier spots on men's scalps has identified a protein involved in male pattern hair loss.

The researchers note that drugs that inhibit the protein are already in development, and it's possible those drugs could one day be used to help men preserve their head of hair.

In the study, researchers from the Perelman School of Medicine at the University of Pennsylvania did an analysis of more than 25,000 genes and honed in on one that produces an enzyme that produces a protein known as PGD2. That protein is present in much higher levels in bald spots.

When scientists placed PGD2 on hair follicles in a petri dish, they found the protein inhibited hair growth.

Researchers then tested the protein on mice genetically engineered to lack a receptor for PGD2, and found that hair growth was unaffected. But when PGD2 was applied to mice that have a different receptor (GPR44), the mice grew less hair.

PGD2 is a type of prostaglandin, or a hormone-like substance known to be involved in many body functions, including regulating the contraction and relaxation of smooth muscle tissue. Drugs that inhibit PGD2, for example, are being studied for use in preventing airway constriction in asthma.

"Several companies have compounds in development that block the receptor for PGD2. Those compounds are being studied to treat asthma," said senior study author Dr. George Cotsarelis, chair and professor of dermatology at University of Pennsylvania School of Medicine in Philadelphia. "We think using these compounds topically . . . could slow down and possibly reverse baldness."

The study is published in the March 21 issue of the journal Science Translational Medicine.

About 80 percent of white men have some degree of hair loss before age 70, according to background information in the study. In balding men, hair follicles don't disappear, but they shrink and produce very small, even microscopic hairs, Cotsarelis explained.

The belief is that something is inhibiting the follicle from growing a normal hair. One of those factors seems to be PGD2, which was found near stem cells in the follicle, which are important in hair growth, Cotsarelis explained.

Dr. Sanusi Umar, a dermatologist in Redondo Beach, Calif. and associate faculty at University of California, Los Angeles, said it's long been known that prostaglandins are involved with hair growth, while this study shows that the opposite may also be true.

For example, Latisse (bimatoprost ophthalmic solution) is a synthetic prostaglandin (mimicking PGF2) that encourages eyelash growth, while Rogaine (minoxidil) is thought to work by promoting the activity of another prostaglandin, PGE2, Umar noted.

"This study tells the other side of the story," he said.

Yet, Umar urged men not to toss out their Rogaine yet. "Yes, this may open another front from which hair loss may be treated. It is not likely to be the panacea, however," he added.

There are likely multiple prostaglandins involved with inhibiting or promoting hair growth, he pointed out. Steroids and nonsteroidal anti-inflammatory drugs also inhibit PGD2 "but have not been shown to consistently grow hair," Umar noted.

"It is more likely that a number of end factors contribute to hair loss with factors like PGD2 inhibiting hair growth and others such as PGE2 and PGF2 promoting it," he said. "PGD2 inhibition may emerge as part of a combined approach used in combination with agents that work via different mechanisms . . . as a more effective approach to hair loss treatment."

More information

The U.S. National Library of Medicine has more on hair loss.