Takahashi Toshie, Mamada Akira, Breakspear Steven, Itou Takashi, Tanji Noriyuki
R&D - Development Research - Hair Care Products Research, Kao Corporation, Tokyo, Japan; The United Graduate School of Drug Discovery and Medical Information Sciences, Gifu University, Gifu, Japan.
J Cosmet Dermatol. 2015 Mar;14(1):2-8. doi: 10.1111/jocd.12129. Epub 2015 Jan 7.
Human hair cuticle is always exposed to various stresses and then gradually lost in daily life. There are two typical patterns of cuticle damage: type L, where the cell membrane complex, the structure located between cuticle cells, is split and the cuticle lifts up, and type E, where the fragile substructure of the cuticle cell (endocuticle) is damaged so that its rugged residue is exposed. We previously reported that type L damage preferentially occurs in the case of Japanese females in their 20s to 40s.
This study aims to elucidate the age-dependent change of cuticle and its effect on hair properties.
Hair fibers collected from Japanese females (ranging from 10 to 70 years old) were evaluated in the aspects of inclination for each type of damage, resistance of cuticle against grooming stresses and content of fatty acid 18-MEA on hair surface.
It was revealed that the dominant damage pattern shifts from type L to E with aging. Furthermore, the cuticle becomes gradually less resistant to daily grooming stress. The dominance of type E damage accelerates cuticle loss. Reduction of 18-MEA on weathered hair is accelerated with aging on elder hair.
It has been reported that various age-dependent changes of whole hair shaft, such as diameter, density, elasticity, etc., occur in the age range of 40s and 50s. In this study, it was revealed that cuticle becomes more fragile and the hair surface properties deteriorate in the same age range.
人发角质层在日常生活中总是暴露于各种应力之下，进而逐渐受损。角质层损伤有两种典型模式：L型，即角质形成细胞之间的细胞膜复合物结构分裂，角质层翘起；E型，即角质形成细胞的脆弱亚结构（内角质层）受损，使其粗糙的残留物暴露。我们之前报道过，L型损伤在20到40岁的日本女性中更为常见。
本研究旨在阐明角质层随年龄的变化及其对头发性能的影响。
对从10到70岁的日本女性收集的头发纤维，在每种损伤类型的倾向、角质层对梳理应力的抗性以及头发表面脂肪酸18 - 甲基二十烷酸（18 - MEA）的含量等方面进行评估。
结果显示，随着年龄增长，主要损伤模式从L型转变为E型。此外，角质层对日常梳理应力的抗性逐渐降低。E型损伤的主导地位加速了角质层的流失。随着年龄增长，老化头发上18 - MEA的减少加速。
据报道，在40多岁和50多岁的年龄段，整个毛干会发生各种随年龄变化的情况，如直径、密度、弹性等。在本研究中，发现在同一年龄段角质层变得更加脆弱，头发表面性能恶化。
