Serotonin activates dermal papilla cells and promotes hair growth.

Serotonin (5-hydroxytryptamine, 5-HT) is a neurotransmitter that plays a vital role in regulating behavior, mood, memory, and gastrointestinal homeostasis. Although recent studies have identified an intestine-hair follicle link, potentially implicating 5-HT, its exact relationship with hair growth remains unclear. Here we investigated the effects of serotonin signaling on hair follicle homeostasis. Gene expression analysis showed significant upregulation of hair growth-related genes in dermal papilla cells treated with 5-HT. The hair growth-promoting effects of 5-HT were examined using hair follicle organoids and hair follicle organ cultures. The addition of 5-HT to hair follicle organoids and hair follicles promoted hair shaft elongation. Similar effects were observed with sumatriptan succinate, a 5-HT receptor agonist. These results suggest that targeting serotonin signaling can advance alopecia therapy.