28. Changes in the Proliferative Activity of Epidermal Melanocytes in Serum-free Primary Culture during the Development of UVB-induced Pigmented Spots in Mice

Tomohisa Hirobe

Keywords: melanoblast, melanocyte, keratinocyte, UVB, proliferation, differentiation

Long-term exposure to ultraviolet radiation B (UVB) induced pigmented spots in the dorsal skin of hairless mice. To clarify the cellular mechanism for the development of these UVB-induced pigmented spots, changes were investigated in the proliferative activity of epidermal melanoblats and melanocytes in the dorsal skin at various weeks after UVB irradiations. Epidermal cell suspensions from the dorsal skin of hairless mice were cultured in a serum-free medium supplemented with dibutyryl adenosine 3':5'-cyclic monophosphate (DBcAMP) and basic fibroblast growth factor (bFGF). The suspensions were prepared from the dorsal skins of mice exposed to UVB for 4 weeks (the stage of hyperpigmentation), and from those of mice 3 (the stage of depigmentation), 8 (the stage of appearance of pigmented spots), 20 (the stage of development of small-sized pigmented spots), and 37 (the stage of development of medium-sized pigmented spots) weeks after the cessation of UVB exposures for 8 weeks. At the stage of hyperpigmentation the proliferative activity of melanocytes was suppressed. With the development of pigmented spots, the proliferative activity of undifferentiated melanoblasts gradually increased, and then followed the increase in the proliferative activity of differentiated melanocytes. These results suggest that the proliferative activity of epidermal melanoblasts and melanocytes in UVB-irradiated skin increase with the development of pigmented spots.

Publications:
Furuya R., Akiu S., Naganuma M., Fukuda M. and Hirobe T.: J. Dermatol., 25, 211-221, 1998.