PHILADELPHIA—Results from a study out of the University of Pennsylvania School of Medicine defined prostaglandin D2 (PGD2)—the product of Prostaglandin D2 synthase (PTGDS) enzyme activity— as an inhibitor of hair growth in androgenetic alopecia (AGA), the testosterone necessary for the development of male pattern baldness (Sci. Transl. Med. 2012;4(126)126ra34).
PTGDS is elevated at the mRNA and protein levels in bald scalp compared to haired scalp of men with AGA. Similarly, PGD2 is elevated in bald scalp. During normal follicle cycling in mice, PTGDS and PGD2 levels increase immediately preceding the regression phase, suggesting an inhibitory effect on hair growth. Researchers showed PGD2 inhibits hair growth in explanted human hair follicles and when applied topically to mice. Hair growth inhibition required the PGD2 receptor G protein (heterotrimeric guanine nucleotide)–coupled receptor 44 (GPR44), but not the PGD2 receptor 1 (PTGDR). Furthermore, researchers found a transgenic mouse, K14-PTGS2, which targets prostaglandin-endoperoxide synthase 2 expression to the skin, demonstrated elevated levels of PGD2 in the skin and developed alopecia, follicular miniaturization, and sebaceous gland hyperplasia, which are all hallmarks of human AGA. The results also suggested the PGD2-GPR44 pathway as a potential target for treatment.
