P44 CHARACTERIZATION OF DEVELOPING HAIR FOLLICLE INDUCED BY CULTURED DERMAL PAPILLA CELLS

¹Endo T., ¹Oomizu S., ¹Inamatsu M., ^1,2Yoshizato K. ¹Hiroshima Tissue Regeneration Project, JST, Japan. ²Dept. of Biol. Sci., Grad. School of Sci., Hiroshima Univ., Hiroshima, Japan.

The dermal papilla (DP) is a mesenchymal compartment of the hair follicle and can induce ectopic hair follicles when it is implanted into the skin. We showed that the rat DP cells are highly proliferative and maintain the hair inducing ability when they are cultured in keratinocyte-conditioned medium or FGF2-containing medium. Previously, we assayed the hair follicle-inducing ability by inserting DP cells between the epidermis and the dermis of the sole skin and transplanting the skin underneath the kidney capsule. However, this method had a limitation, because hair follicles were induced in some sham-operated control samples.

In this study, we established a new method in which the sole skins were grafted onto the back skin of nude mice. Two weeks after implantation, the epithelium began to surround the DP cells. While the first morphological change of hair development in embryos is the budding of the epithelium, this process was not observed in implants. The epidermal surrounding advanced during the next 1 week, and the shape developed into hair follicle-like structure at 4 weeks. Such changes were never found in negative controls, suggesting that this method is more faithful than the previous one.

We characterized the hair-induction process at the gene expression level. Gene of shh was expressed in the anterior part of the normal hair matrix. Its expression in implants was also found in one side of the hair matrix-like part. The expression pattern of shh and other molecular markers showed that the structure induced by DP cells mimics properly the process of normal development of hair follicles. This method would be useful to study hair formation, particularly initiation of the hair development.