The action of a cosmetic hair treatment on follicle function

OBJECTIVEHuman hair changes with age: fibre diameter and density decrease, hair growth slows and shedding increases. This series of controlled studies examined the effect on hair growth parameters of a new leave-on hair treatment (LOT) formulated with DynagenTM (containing hydrolysed yeast protein) and zinc salts.\n\nMETHODSHair growth data were collected from healthy women aged 18-65 years. The LOTs effect on hair growth was measured in a randomized double-blind study and in hair samples; its effect on follicle-cell proliferation was assessed by quantifying Ki67 expression in scalp biopsies. The LOTs effect on plucking force was determined in an ex vivo model. Dynagens effect on the expression of the tight-junction marker claudin-1 was analysed in cultured follicles. The effect on protease activity of zinc salts used in the LOT was examined in vitro.\n\nRESULTSHair growth rate decreased with increasing subject age. The LOT significantly increased hair growth rate, fibre diameter, bundle cross-sectional area, Ki67 expression and the plucking force required to remove hair. Dynagen significantly increased claudin-1 expression in cultured follicles. Protease activity was reduced by zinc salts.\n\nCONCLUSIONThe Dynagen-based LOT increases hair-fibre diameter, strengthens the follicular root structure and increases hair growth rate.