Balding causes widespread psychological distress but is poorly controlled. The commonest treatment, minoxidil, was originally an antihypertensive drug that promoted unwanted hair. We hypothesized that another serendipitous discovery, increased eyelash growth side-effects of prostamide F(2α)-related eyedrops for glaucoma, may be relevant for scalp alopecias. Eyelash hairs and follicles are highly specialized and remain unaffected by androgens that inhibit scalp follicles and stimulate many others. Therefore, we investigated whether non-eyelash follicles could respond to bimatoprost, a prostamide F(2α) analog recently licensed for eyelash hypotrichosis. Bimatoprost, at pharmacologically selective concentrations, increased hair synthesis in scalp follicle organ culture and advanced mouse pelage hair regrowth in vivo compared to vehicle alone. A prostamide receptor antagonist blocked isolated follicle growth, confirming a direct, receptor-mediated mechanism within follicles; RT-PCR analysis identified 3 relevant receptor genes in scalp follicles in vivo. Receptors were located in the key follicle regulator, the dermal papilla, by analyzing individual follicular structures and immunohistochemistry. Thus, bimatoprost stimulates human scalp follicles in culture and rodent pelage follicles in vivo, mirroring eyelash behavior, and scalp follicles contain bimatoprost-sensitive prostamide receptors in vivo. This highlights a new follicular signaling system and confirms that bimatoprost offers a novel, low-risk therapeutic approach for scalp alopecias.

Topical minoxidil has been successfully used to treat androgenetic alopecia. It can also be applied to enhance eyebrows. However, there is no study comparing minoxidil lotion with placebo for eyebrow enhancement. In this trial, we determined the efficacy and safety of minoxidil 2% lotion for eyebrow enhancement compared with placebo. Forty patients were randomized for minoxidil on the eyebrow on one side of the face and placebo on the other. Efficacy was evaluated by global photographic assessment, eyebrow diameter, eyebrow count and subject's satisfaction. Side-effects were also evaluated. Thirty-nine patients (97.5%) completed the study. After 16 weeks, the minoxidil group achieved significantly better results in all measured outcomes compared to the placebo group. Side-effects were minor and did not preclude patients from continuing the study. Our study suggests that minoxidil 2% lotion is a safe and effective treatment for eyebrow hypotrichosis.

© 2014 Japanese Dermatological Association.