Published in The Hindu on March 22, 2012

Scientists have finally identified the culprits that are responsible for causing baldness in men. They are a protein known as prostaglandin D2, also known as PGD2 and its derivative (15-dPGJ2).  Incidentally, the protein and its derivative were found to show the same effect in mice as well.

The results are published today (March 22) in Science Translational Medicine.

Researchers from the University of Pennsylvania found that the protein inhibits hair growth. In fact, its level “increases immediately preceding the regression phase,” they write.  Its level in the scalp of balding men increases nearly three times compared to those who are not bald. “The absolute level of PGD2 [protein] was 16.3 ng/g tissue in balding scalp and 1.5 ng/g tissue in haired scalp,” the paper notes.

The scientists tested their hypothesis using explanted human hair follicles in culture for a week. They used different amounts of both the proteins and its derivative to check their effects.

At low levels (5 micromolar) of the medium, the protein and its derivative “significantly inhibited hair growth.” The hair became shorter when 10 micromolar of the protein was used.  But at the same concentration, the derivative “completely inhibited all hair growth.”

Different prostaglandins have been known to regulate and increase hair growth.  In fact one such prostaglandin has been approved by the FDA to enhance hair growth in human eyelashes. And another is supposed to protect mice from radiation-induced hair loss.

But this study has shown that both in mouse and human skin a balance between the two prostaglandins — PGE2 and PGD2 — is required. There may be other causes for baldness, they note.

The study provides the first ray of hope to people who show early signs of balding. The authors suggest that the level of PGE2 should be increased while inhibiting PGD2 signalling.  “Our findings also suggest that supplemental PGE2 could be therapeutic,” they write.  They also note that increasing its level in the bald scalp can go as far as overcoming the inhibitory effect of the protein PGD2. The act of inhibiting PGD2 level “may prevent miniaturization and provide benefit to those in the process of balding.”

But they have almost dashed the hopes of people who are already bald. “It is unclear whether men who are already bald will regrow hair,” they write.