1. ^*Department of Dermatology, Tokyo Women's Medical University, Tokyo
2. ^†Kao Biological Science Laboratories, Tochigi, Japan

Correspondence: Genji Imokawa, PhD, Biological Science Laboratories, Kao Corporation, 2606 Akabane, Ichikai-machi, Haga, Tochigi 321–34, Japan. Email: imokawag@dream.ocn.ne.jp

Received 24 April 2003; Revised 2 December 2003; Accepted 5 December 2003; Published online 5 May 2004.

Abstract

We previously reported that accentuated expression of the endothelin-1 (ET-1)/endothelin B receptor (ET_BR) cascade is involved in the mechanism of hyperpigmentation in lentigo senilis (LS) lesions. The paracrine mechanism underlying ultraviolet B (UVB)-induced hyperpigmentation in the skin may involve the stimulation of the ET-1/ET_BR cascade as well as the stem cell factor (SCF)/SCF receptor cascade. Therefore, we used RT-PCR and immunohistochemistry to determine whether accentuated expression of the SCF/SCF receptor cascade is also associated with the mechanism of hyperpigmentation in epidermal LS lesions. RT-PCR analysis demonstrated the increased expression of mRNA transcripts for SCF (n=7), but not for SCF receptor (n=6) or growth-related oncogene (GRO) (n=4) in LS lesions. Immunohistochemistry revealed markedly stronger staining for SCF but not for GRO or basic fibroblast growth factor (bFGF) in the lesional epidermis compared with the perilesional epidermis. This increased staining for SCF was corroborated by western blotting analysis for SCF expression in the lesional epidermis. These findings suggest that in addition to the stimulated expression of the ET-1/ET_BR cascade, the accentuated expression of SCF in lesional skin plays an important role in the mechanism involved in the epidermal hyperpigmentation of LS.