P1.151

DISTRIBUTION OF MERKEL CELLS DURING HUMAN HAIR FOLLICLE MORPHOGENESIS

Y. Tanaka, H. Oura, H. Takeichi, Y. Fujii, S. Arase

Dep. of Dermatology, School of Medicine, The University of Tokushima, Tokushima, Japan

Objective and Methods: The origin and functions of Merkel cells in the skin is still uncertain, although current studies have shown that they express simple epithelium-type cytokeratins (CKs) and have morphological variation, such as oval and dendritic cell types. Specific monoclonal antibodies against these CKs allow histological studies of Merkel cells at the light microscopical level. It has been shown that groups of Merkel cells were located in the deep infundibulum and in the deep isthmus/ bulge area in hair follicles of human adult scalp. However little information is available about the distribution of Merkel cells during the hair follicle morphogenesis. In this study, we immunohistochemically examined the distribution of CK 20 immunoreactive cells (Merkel cells) in developing hair follicles in human fetal skin, ranging in age from 9 week to 24 week estimated gestational age (EGA).

Results and Conclusion: No Merkel cells were observed in the germinative layer of 9 week EGA. During the hair follicle morphogenesis, a few Merkel cells were found in the condensation of epithelial cells at the hair germ stage, and in the outermost layer of the peg at the hair peg stage to the bulbous hair peg stage. In hair follicles at the further advanced stage, they clustered around the upper portion of infundibulum, and located in bulge area. A few Merkel cells were present within interfollicular epidermis in each developing stage. Morphologically, both oval and dendritic cell type Merkel cells were observed during the process of hair follicle morphogenesis. These results suggest that Merkel cells might contribute to the formation and development of hair follicles in fetal skin.