P-08   EMBRYONIC DERMAL CONDENSATION AND CULTURED DERMAL PAPILLA CELLS INDUCE ADULT EPIDERMIS TO HAIR FOLLICLES THROUGH DIFFERENT MECHANISMS

M. Inamatsu1,2,3,4, A. Makabe4, K. Toyoshima1,2, T. Endo3, S. Oomizu3, K. Yoshizato1,3,4 Innovation plaza Hiroshima, JST1, Hiroshima, Institute of Immunology Co., Ltd.2, Tokyo, Hiroshima Tissue Regeneration Project3, Hiroshima Prefecture Collaboration of Regional Entities for the Advancement of Technological Excellence, JST, Hiroshima, and Dept. of Biol. Sci., Grad. School of Sci.4, Hiroshima Univ., Hiroshima. Japan.

Embryonic hair follicles are formed by a series of interactions between the epidermis and the underlying mesenchymal tissue. The first morphological indication in the genesis of embryonic hair follicles is the formation of placode and hair germ in the epidermal compartment and the tissue condensation in the mesenchymal compartment. We previously showed that the adult sole epidermis combined with embryonic dermis at 17 days post coitus containing dermal condensations produced hairs when transplanted onto the back of nude mice and allowed to grow there. This result indicates that the dermal condensation is able to induce the afollicular epidermis to differentiate into follicular epidermis. Histology on the induction process showed the formation of placode-like tissues at 10 days post-transplantation. Thus, it seems that the recombinant transplant produces hair follicles through a mechanism similar to that underlying the hair follicle development in the embryonic skin. Previously, we demonstrated the hair follicle-inducing ability of adult dermal papilla (DP) cells. The adult rat sole skin was inserted with cultured DP cells between its epidermis and dermis, transplanted onto the back of nude mice, and allowed to grow for 4 weeks. Hair follicles were developed in the transplants. Histology showed the epidermis surrounded the aggregates of DP cells at 2 weeks after transplantation. The epidermis never formed placode-like tissues, but grew up and developed into hair follicle-like structures at 4 weeks. Histological evidence showed that the hair follicle-induction process by adult DP cells mimics the process of new hair development at the early anagen of hair cycle. Thus, we conclude that embryonic dermal condensations induce the adult affolicular epidermis to differentiate into hair follicles through a mechanism different from that acting on the epidermis during the induction by adult dermal papillae.