12.    A model for hair morphogenesis. 
Jizeng Qiao, Erica Philips, Jeff Teumer, Intercytex Ltd., Woburn, MA, USA

In this study, we have developed a model to examine hair morphogenesis. The assay combines an intact donor epidermis with a suspension of dermal cells, which could be from a variety of donors. The epidermis and the dermal cells are applied to a subcutaneous graft bed created on a dorsal skin flap. When the flap is repositioned over the graft, the graft is in a subcutaneous position such that it is protected after implantation. The assay is simple to perform and overcomes some of the limitations of other assays for hair induction. Using the assay, both freshly isolated and cultured dermal cells as well as cultured dermal papilla cells from several species all induced hair development. The induced hairs were aesthetically indistinguishable from those of the epidermal donor in length, thickness, and pigmentation, and they were also histologically normal. Time course studies show that the process of hair morphogenesis in the grafts was similar to embryonic hair morphogenesis. In addition to serving as a convenient test for the hair inductive capacity of dermal papilla cells, the assay may also be used to examine specific cellular and molecular interactions during hair morphogenesis, such as epithelial-mesenchymal interactions and melanogenesis.