Takaaki Yamada1, Seiji Hasegawa2, Yu Inoue3, Yasushi Date3, Masaru Arima4, Akiko Yagami4, Yohei Iwata4, Masamichi Abe4, Masayuki Takahashi4, Naoki Yamamoto5, Hiroshi Mizutani3, Satoru Nakata3, Kayoko Matsunaga4, Hirohiko Akamatsu6. 1. Research Laboratories, Nippon Menard Cosmetic Co., Ltd., 2-7 Torimicho, Nishi-ku, Nagoya, Aichi, Japan; Department of Dermatology, Fujita Health University School of Medicine, 1-98 Kutsukakecho, Toyoake, Aichi, Japan; Department of Applied Cell and Regenerative Medicine, Fujita Health University School of Medicine, 1-98 Kutsukakecho, Toyoake, Aichi Japan. Electronic address: yamada.takaaki@menard.co.jp. 2. Research Laboratories, Nippon Menard Cosmetic Co., Ltd., 2-7 Torimicho, Nishi-ku, Nagoya, Aichi, Japan; Department of Dermatology, Fujita Health University School of Medicine, 1-98 Kutsukakecho, Toyoake, Aichi, Japan; Department of Applied Cell and Regenerative Medicine, Fujita Health University School of Medicine, 1-98 Kutsukakecho, Toyoake, Aichi Japan. 3. Research Laboratories, Nippon Menard Cosmetic Co., Ltd., 2-7 Torimicho, Nishi-ku, Nagoya, Aichi, Japan. 4. Department of Dermatology, Fujita Health University School of Medicine, 1-98 Kutsukakecho, Toyoake, Aichi, Japan. 5. Laboratory of Molecular Biology & Histochemistry, Fujita Health University Joint Research Laboratory, 1-98 Kutsukakecho, Toyoake, Aichi, Japan. 6. Department of Applied Cell and Regenerative Medicine, Fujita Health University School of Medicine, 1-98 Kutsukakecho, Toyoake, Aichi Japan.
Abstract
BACKGROUND: Solar lentigines (SLs) are characterized by hyperpigmented macules, commonly seen on sun-exposed areas of the skin. Although it has been reported that an increase in the number of melanocytes and epidermal melanin content was observed in the lesions, the following questions remain to be answered: (1) Is acceleration of melanogenesis in the epidermis caused by an increased number of melanocytes or the high melanogenic potential of each melanocyte? (2) Why does the number of melanocytes increase? OBJECTIVE: To elucidate the pathogenic mechanism of SLs by investigating the number, melanogenic potential and proliferation status of the melanocyte lineage in healthy skin and SL lesions. METHODS: Immunostaining for melanocyte lineage markers (tyrosinase, MART-1, MITF, and Frizzled-4) and a proliferation marker, Ki67, was performed on skin sections, and the obtained images were analyzed by image analysis software. RESULTS: The expression level of tyrosinase to MART-1 of each melanocyte was significantly higher in SL lesions than healthy skin. The numbers of melanocytes in the epidermis, melanoblasts in the hair follicular infundibulum and melanocyte stem cells in the bulge region were increased in SL; however, no significant difference was observed in the Ki67-positive rate of these cells. CONCLUSION: The melanogenic potential of each melanocyte was elevated in SL lesions. It was suggested that the increased number of melanocytes in the SL epidermis might be attributed to the abnormal increase of melanocyte stem cells in the bulge.
BACKGROUND: Solar lentigines (SLs) are characterized by hyperpigmented macules, commonly seen on sun-exposed areas of the skin. Although it has been reported that an increase in the number of melanocytes and epidermal melanin content was observed in the lesions, the following questions remain to be answered: (1) Is acceleration of melanogenesis in the epidermis caused by an increased number of melanocytes or the high melanogenic potential of each melanocyte? (2) Why does the number of melanocytes increase? OBJECTIVE: To elucidate the pathogenic mechanism of SLs by investigating the number, melanogenic potential and proliferation status of the melanocyte lineage in healthy skin and SL lesions. METHODS: Immunostaining for melanocyte lineage markers (tyrosinase, MART-1, MITF, and Frizzled-4) and a proliferation marker, Ki67, was performed on skin sections, and the obtained images were analyzed by image analysis software. RESULTS: The expression level of tyrosinase to MART-1 of each melanocyte was significantly higher in SL lesions than healthy skin. The numbers of melanocytes in the epidermis, melanoblasts in the hair follicular infundibulum and melanocyte stem cells in the bulge region were increased in SL; however, no significant difference was observed in the Ki67-positive rate of these cells. CONCLUSION: The melanogenic potential of each melanocyte was elevated in SL lesions. It was suggested that the increased number of melanocytes in the SL epidermis might be attributed to the abnormal increase of melanocyte stem cells in the bulge.
Authors: R Schütz; A V Rawlings; E Wandeler; E Jackson; S Trevisan; J-M Monneuse; I Bendik; M Massironi; D Imfeld Journal: Int J Cosmet Sci Date: 2019-06 Impact factor: 2.970