029 Multipotent stem cell and hair follicle morphogenesis.

H. Oshima1,2 and Y. Barrandon1 1Department of Biology, Ecole Normale Supérieure, Paris, France 2Department of Plastic Surgery, St Marianna University School of Medicine, Kawasaki, Japan

Hair follicles are self-renewing skin appendages that contain stem cells. Several lines of evidence indicate that stem cells reside in the upper part of the follicle. In the pelage follicle of the mouse, 3HtdR or BrdU-labeling experiments have revealed that slow cycling cells reside in the bulge. Clonal analysis has demonstrated that 95% of the colony forming cells of rat vibrissal follicle are located in the bulge. Furthermore, the cells located in this region proliferate infrequently to the opposite of those located in the hair matrix which proliferate actively. These previous works led us to questions if the bulge serve as a reservoir of stem cells to sustain hair growth and there is a flux of stem cells from the bulge to the bulb. OF1, B6/D2F1/Jico, athymic mice and Rosa26 mice that constitutively express lacZ gene were obtained and bred in our animal facility. We have microdissected the bulge of vibrissal follicles from wildtype mice and replaced them with bulges of Rosa26. Chimeric follicles were then transplanted under the kidney capsula of athymic mice. Eventually the bulges of Rosa26 follicles were transplanted in utero onto the back of embryos of OF1. Several weeks after operation, their kidneys with implant of follicles and the bulge-transplanted back skin of embryos were harvested and fixed with 4% paraformaldehyde, then were stained in X-gal solution. Over 6-8 weeks after implantation, all the lineages involved in the formation of a pilo-sebaceous units were constantly generated from the transplanted bulges. Furthermore, epidermis, multiple hair follicles and sebaceous glands formed when the bulges of Rosa26 follicles were transplanted onto the back of mouse embryos. We demonstrate i) that multipotent stem cells are present in the bulge of vibrissal follicles of adult mice, ii) that they can generate epidermis, all hair follicle lineages and sebaceous glands, iii) that they migrate in the outer root sheath from the bulge down to the hair bulb to participate in whisker growth. These results suggest important implications in skin morphogenesis andplasticity of stem cells.