Ageratum houstonianum Extract and Agerarin Promote Hair Growth via MAPK/AP-1 Axis-Dependent Upregulation of SCUBE3 in Human Dermal Papilla Cells

Dermal papilla (DP) cells orchestrate hair follicle growth and cycling by secreting signaling molecules that stimulate follicular epithelial stem cells. The signal peptide CUB-EGF-like domain-containing protein 3 (SCUBE3) was recently identified as a potent anagen stimulator secreted by DP cells. Ageratum houstonianum ethanolic extract (AHE) and its active constituent agerarin exhibit anti-inflammatory properties; however, their effects on hair follicle growth remain unclear. This study aimed to investigate the effects of AHE and agerarin on SCUBE3 expression in primary human DP cells and to elucidate the underlying molecular signaling pathway. Cell viability was assessed by measuring cell confluency. Ex vivo hair growth was analyzed using organ cultures of human hair follicles. Gene and protein expression were determined using reverse transcription-PCR, immunoblot analysis, immunofluorescent staining, tyramide signal amplification-based multiplex immunohistochemistry, and gene promoter-reporter assay in primary human follicle DP cells. In a hair follicle organ culture model, both AHE and agerarin increased the population of the anagen phase and promoted hair shaft elongation. AHE and agerarin significantly upregulated SCUBE3 expression at both the mRNA and protein levels. Mechanistically, AHE and agerarin induced activator protein-1 (AP-1) expression by activating mitogen-activated protein kinase signaling pathways, thereby increasing SCUBE3 gene promoter activity. AHE and agerarin promoted hair follicle growth by upregulating SCUBE3 expression via activation of the MAPK–AP-1 signaling axis. In conclusion, AHE and agerarin may serve as potential therapeutic agents for the prevention and treatment of alopecia (hair loss).