Camellia japonica seed extract promotes hair growth by preventing dermal papilla cell senescence and activating hair follicle stem cells

Abstract Camellia japonica has various beneficial effects on the skin and hair; hence, it is widely used for hair care. However, the cellular mechanism(s) underlying these effects remains elusive. In this study, we aimed to confirm the efficacy of C. japonica seed extract (CJSE) in promoting hair growth and determine the action mechanism. CJSE was prepared using Camellia seed cake, and the components were analyzed through high-performance liquid chromatography. CJSE and its main components, camelliasaponins B1 and B2, significantly promoted the proliferation of human hair follicle dermal papilla cells and hair elongation in cultured human hair follicles. They also prevented cellular senescence and DNA damage caused by a hair loss-inducing factor, dihydrotestosterone (DHT), via the p16 INK4a -pRb pathway in human hair follicle dermal papilla cells. Moreover, CJSE restored the activities of human hair follicle stem cells (HFSCs) repressed by a DHT-treated dermal papilla cell-conditioned medium. It also directly activated human HFSCs by downregulating p21 expression. A clinical trial involving patients with pattern hair loss showed a significant increase in total hair count in the CJSE-treated group after 24 weeks. CJSE stimulates hair growth by preventing premature senescence of human hair follicle dermal papilla cells and upregulating the activation of human HFSCs. These results suggest that CJSE can be used as a novel functional ingredient for preventing male and female pattern hair loss.