Acquired curved hair is caused by fusion of multiple hair matrix cells.

BACKGROUND: "Curved hair" caused by acquired factors is considered to have adverse cosmetic effects, but the detailed mechanism behind curved hair remains obscure. OBJECTIVE: We attempted to clarify the causes of curved hair that appeared to have occurred via acquired factors. METHODS: Outer root sheath cells (ORSC) isolated from plucked human hair follicles were used to evaluate the expression of type IV collagen. Straight and curved hairs with hair follicle tissue attached were also collected from the same individuals and subjected to morphological, immunohistochemical, and gene expression analyses. RESULTS: The amount of type IV collagen increased upon inducing endoplasmic reticulum stress in ORSC. Meanwhile, in curved hair follicle tissue, the gene expression of type IV collagen decreased. In addition, the curved hair follicle tissue obtained from participants in their 30 s to 50 s had distorted shapes compared with that of straight hair from the same individuals. It was also observed that hair matrix cells based on multiple hair germs fused to eventually form a single hair follicle and hair shaft. In curved hair follicle tissue, KRT71 protein, a marker of inner root sheath differentiation, was unevenly distributed and there was elevated expression of Dickkopf-1 (DKK1) protein, an inhibitor of the Wnt signaling pathway. CONCLUSION: Our study revealed the fusion of hair matrix cells during hair follicle regeneration as a cause of acquired curved hair. We consider that such fusion causes hair follicle tissue to abnormally differentiate, resulting in asymmetric hair follicle shapes and curved hair.

Induction of melanogenesis by 4'-O-methylated flavonoids in B16F10 melanoma cells.

Agents to control melanogenesis are in demand for the development of cosmetics to improve pigmentation disorders of skin and hair. In this study, we examined and evaluated the effects of flavonoids on melanogenesis in the melanogenic cells model, murine B16F10 melanoma cells. In the course of this study, we found that incubation of the cells in a medium containing 10 µM of the 4'-O-methylated flavonoids, diosmetin (4'-O-methylluteolin), acacetin (4'-O-methylapigenin) or kaempferide (4'-O-methylkaempferol), increased the melanin contents of the cells 3- to 7-fold higher than the control cells. The concentration-dependence test revealed that 20 µM acacetin showed the highest effect, up to 33-fold higher than the vehicle. On the other hand, the corresponding 4'-OH-type flavonoids, luteolin, apigenin and kaempferol, had a significantly smaller effect. Furthermore, by evaluating the melanogenic proteins, we found that the cells treated with 4'-O-methylated flavonoids showed higher tyrosinase activity, as well as upregulation of tyrosinase expression, preceded by activation of cAMP response element binding protein (CREB) and extracellular signal-regulated kinases types 1 and 2 (ERK1/2). These results indicate that the 4'-O-methyl group of flavonoids plays an important role in the induction of melanogenesis by activating its major signal transduction pathway through the upregulation of phospho-CREB in murine B16F10 melanoma cells.