Keratinocytes Control the Proliferation and Differentiation of Cultured Epidermal Melanocytes from Ultraviolet Radiation B‐Induced Pigmented Spots in the Dorsal Skin of Hairless Mice

Abstract

Long-term exposure of ultraviolet radiation B (UVB)-induced pigmented spots in the dorsal skin of hairless mice of Hos:(HR-1 X HR//De) F1. Previous study showed that the proliferative and differentiative activities of cultured epidermal melanoblasts/melanocytes from UVB-induced pigmented spots increased with the development of the pigmented spots. To determine whether the increase in the proliferative and differentiative activities of epidermal melanoblasts/melanocytes was brought about by direct changes in melanocytes, or by indirect changes in surrounding keratinocytes, pure cultured melanoblasts/melanocytes and keratinocytes were prepared and co-cultured in combination with control and irradiated mice in a serum-free culture medium. Keratinocytes from irradiated mice stimulated the proliferation and differentiation of both neonatal and adult non-irradiated melanoblasts/melanocytes more greatly than those from non-irradiated mice. In contrast, both non-irradiated and irradiated adult melanocytes proliferated and differentiated similarly when they were co-cultured with irradiated adult keratinocytes. These results suggest that the increased proliferative and differentiative activities of mouse epidermal melanocytes from UVB-induced pigmented spots are regulated by keratinocytes, rather than melanocytes.

Immunohistochemical survey of the distribution of epidermal melanoblasts and melanocytes during the development of UVB-induced pigmented spots

“…We have shown that the proliferative activity of epidermal melanoblasts and melanocytes in serum-free primary culture [25,26] changes during the development of pigmented spots induced by UVB irradiation [27], and keratinocytes are involved in regulating this process [28][29][30]. However, little is known about the stages of differentiation of melanoblasts or melanocytes present in the pigmented spots.…”

Prevention of the Ultraviolet B-Mediated Skin Photoaging by a Nuclear Factor κB Inhibitor, Parthenolide

“…It is well known that the UV-induced epidermal hyperplasia, consisting of the hyperproliferative keratinocytes and melanocytes (Brenneisen et al, 2002;Chung, 2003;Hirobe et al, 2003) is considered to be due to the action of bFGF induced by UVB (Pittelkow and Shipley, 1989;Bielenberg et al, 1998). In Fig.…”

“…The UV-irradiated skin is characterized by fine and coarse wrinkling, roughness, dryness, laxity, and pigmentation (Chung, 2003). Microscopically, these changes can be explained by keratinocyte hyperproliferation and degradation of collagen fibers (Brenneisen et al, 2002), causing skin wrinkling and laxity, and melanocyte proliferation that leads to pigmentation characterized by dysregulation of melanocyte homeostasis and increase in the melanocyte density (Hirobe et al, 2003). The UV-induced production of proinflammatory cytokines, such as interleukin-1 (IL-1) and tumor necrosis factor ␣ (TNF␣), has been considered attributable to these changes (Corsini et al, 1997;Yarosh et al, 2000).…”

Inhibitory Effect of Hydroxysafflor Yellow A on Mouse Skin Photoaging Induced by Ultraviolet Irradiation

“…3,34,35 The inhibitory effect of HSYA on UV-induced epidermal hyperproliferation was evaluated by directly measuring the thickness of epidermis. The results are shown in Fig.…”