Involvement of Transglutaminase 3 (TG3) in Hair Stiffness Changing with Age by Capture of Zinc

Abstract

We previously reported that zinc in the cuticle of hair contributes to hair stiffness, and the agedependent decrease in zinc is one of the reasons for the reduction in hair stiffness. From the results, we speculated that the decrease of zinc in the cuticle with aging may be caused by a decline of proteins that retain zinc in the cuticle. We extracted proteins from hair cuticle and analyzed them by mass spectrometry, revealing transglutaminase 3 (TG3) as a zinc-retaining candidate protein. The binding of TG3 to zinc was confirmed using a size fractionation column followed by ICP-MS, and the immunostaining of longitudinal sections of hair root demonstrated the presence of significant amounts of TG3 in the cuticle. Furthermore, hairs from volunteers of various ages were analyzed for the expression of TG3 mRNA in the hair roots, showing a downturn trend of the expression after their 40s and beyond. Based on the results, we concluded that the decrease of zinc in hair with aging past one's 40s is partly due to the decline of the TG3 expression that could retain zinc. In the future, the use of compounds that induce TG3 expression, could become a novel solution to maintain, or even regain hair firmness, resulting from the prevention of zinc loss with aging.