P-07   EXPRESSION OF ALPHA-MELANOCYTE STIMULATING HORMONE IN BULGE REGION OF MOUSE VIBRISSAL FOLLICLES

M. Kono, J. Ito*, Y. Osamura*, S. Kawana. Department of Dermatology, Nippon Medical School, Tokyo Japan. *Department of Pathology, Tokai University, School of Medicine, Kanagawa Japan.

Skin is a prominent extrapituitary source and a target for proopiomelanocortin (POMC) products. Hair follicles also express POMC gene and produce of POMC peptides such as ACTH and alpha-MSH. These consist of a epithelial core formed of several layers including the outer root sheath (ORS), surrounded by messenchymal sheath. The bulge is located at the upper reagion of ORS in vibrissal follicles. This region contains stem cells of the follicular keratinocytes and plays important roles for hair morphogenesis. Previously, alpha-MSH was found in the ORS of anagen follicles by immunostaining. But it has not been known whether alpha-MSH expresses in the bulge. Here we demonstrate three-dimensional localization of alpha-MSH expression in the vibrissal follicles of C57BL/6 mice. Using confocal laser microscopy, we show alpha-MSH is expressed predominantly in the bulge region. Since ACTH injection is known to induce hair growth in mice and high dose of MSH modulate keratinocyte proliferation in murine skin organ culture, intrafollicularly generated ACTH and alpha-MSH may operate as hair growth modulators. Furthermore recent report revealed that hair folllicle melanocytes are located in the ORS, the hair matrix above the dermal papilla and in the bulge, and the last population may be hair follicle melanocyte stem cells. Therefore our result indicates that alpha-MSH may modulate hair growth and attendant melanogenesis in the vibrissal hair follicles.