Hair Growth Promoting Effect of Hottuynia cordata Extract in Cultured Human Hair Follicle Dermal Papilla Cells

Houttuynia cordata (HC) is a traditional oriental herbal medicinal plant widely used as a component of complex prescriptions in Asia for alopecia treatment. The effect of HC on hair growth and its underlying mechanism, however, have not been demonstrated or clarified. In this study, we investigated the hair growth promoting effect of HC in cultured human dermal papilla cells (hDPCs). HC extract was found to stimulate the proliferation of hDPCs and this stimulation might be in part a consequence of activated cellular energy metabolism, because treatment of HC extract increased the generation of nicotinamide adenine dinucleotide (NADH) and ATP through increasing the mitochondrial membrane potential (ΔΨ). In the context of cell cycle, HC extract increased the expression of CDK4 and decreased the expression of CCNA2 and CCNB1, implying that HC extract might induce G1 phase progression of DPCs which resulted in enhanced proliferation. HC extract increased the expression of Bcl2 essential for maintaining hair follicle anagen stage and cell survival. On the contrary, the expression of p16 and p21 was down-regulated by HC extract. In addition, HC extract enhanced the secretion of platelet-derived growth factor (PDGF)-aa and vascular endothelial growth factor (VEGF) and induced phosphorylation of extracellular signal-regulated kinase (ERK) and AKT. Furthermore, HC extract prolonged anagen stage in organ cultured human hair follicles. Our data strongly suggest that HC extract could support hair growth by stimulating proliferation of DPCs and elongating anagen stage, resulted from enhanced cellular energy metabolism and modulation of gene expression related to cell cycle, apoptosis, and growth factors.