title: Comprehensive analysis of melanogenesis and proliferation potential of melanocyte lineage in solar lentigines.
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.
  
  
  CONCLUSIONS
  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: 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.
authors: Takaaki
authors: T
authors: Yamada
authors: 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.
authors: Seiji
authors: S
authors: Hasegawa
authors: Research Laboratories, Nippon Menard Cosmetic Co., Ltd., 2-7 Torimicho, Nishi-ku, Nagoya, Aichi, Japan.
authors: Yu
authors: Y
authors: Inoue
authors: Research Laboratories, Nippon Menard Cosmetic Co., Ltd., 2-7 Torimicho, Nishi-ku, Nagoya, Aichi, Japan.
authors: Yasushi
authors: Y
authors: Date
authors: Department of Dermatology, Fujita Health University School of Medicine, 1-98 Kutsukakecho, Toyoake, Aichi, Japan.
authors: Masaru
authors: M
authors: Arima
authors: Department of Dermatology, Fujita Health University School of Medicine, 1-98 Kutsukakecho, Toyoake, Aichi, Japan.
authors: Akiko
authors: A
authors: Yagami
authors: Department of Dermatology, Fujita Health University School of Medicine, 1-98 Kutsukakecho, Toyoake, Aichi, Japan.
authors: Yohei
authors: Y
authors: Iwata
authors: Department of Dermatology, Fujita Health University School of Medicine, 1-98 Kutsukakecho, Toyoake, Aichi, Japan.
authors: Masamichi
authors: M
authors: Abe
authors: Department of Dermatology, Fujita Health University School of Medicine, 1-98 Kutsukakecho, Toyoake, Aichi, Japan.
authors: Masayuki
authors: M
authors: Takahashi
authors: Laboratory of Molecular Biology & Histochemistry, Fujita Health University Joint Research Laboratory, 1-98 Kutsukakecho, Toyoake, Aichi, Japan.
authors: Naoki
authors: N
authors: Yamamoto
authors: Research Laboratories, Nippon Menard Cosmetic Co., Ltd., 2-7 Torimicho, Nishi-ku, Nagoya, Aichi, Japan.
authors: Hiroshi
authors: H
authors: Mizutani
authors: Research Laboratories, Nippon Menard Cosmetic Co., Ltd., 2-7 Torimicho, Nishi-ku, Nagoya, Aichi, Japan.
authors: Satoru
authors: S
authors: Nakata
authors: Department of Dermatology, Fujita Health University School of Medicine, 1-98 Kutsukakecho, Toyoake, Aichi, Japan.
authors: Kayoko
authors: K
authors: Matsunaga
authors: Department of Applied Cell and Regenerative Medicine, Fujita Health University School of Medicine, 1-98 Kutsukakecho, Toyoake, Aichi Japan.
authors: Hirohiko
authors: H
authors: Akamatsu
mesh_terms: D000328:Adult; D000368:Aged; D019070:Cell Lineage; D049109:Cell Proliferation; D005260:Female; D018859:Hair Follicle / Q000166:cytology; D006801:Humans; D007911:Lentigo / Q000473:pathology*; D008297:Male; D008543:Melanins / Q000096:biosynthesis*; D008544:Melanocytes / Q000166:cytology* / Q000378:metabolism; D008875:Middle Aged; D013472:Sunlight / Q000009:adverse effects*
chemical_list: D008543:Melanins
keywords: Differentiation; Melanoblast; Melanocyte; Melanocyte stem cell; Solar lentigines