P4.38 HAIR CYCLES FOUND IN THE LOWER FRAGMENTS OF VIBRISSAL FOLLICLES GRAFTED BENEATH THE KIDNEY CAPSULE

Machiko Lida¹, Setsunosuke Ihara² and Takashi Matsuzaki²

¹Division of Resources Life Science, United Graduate School of Agricultural Science, Tottori University, Tottori, Japan, ²Faculty of Life and Environmental Science, Shimane University, Matsue, Japan

Objectives: We studied whether transit amplifying cells (TA cells) in lower vibrissal follicles (VFs) could survive apoptosis throughout the regression phase and behave as a source of the matrix cells needed for the subsequent anagen phase.

Methods: The distal portions including the bulge region were separated from VFs in various hair cycles and discarded. The remaining lower VFs were transplanted beneath the kidney capsule of recipient mice. After several weeks, the grafts were photographed and the number of hairs that were produced assessed. Whole VFs were also grafted as controls.

Results: We observed a whole VF graft with 5 hairs after 12 weeks of transplantation, suggesting progression of four rounds of hair cycles in it. Interestingly, two hairs were produced in lots of lower VF fragments by 6-8 weeks after grafting, despite the fact that they had not contained the bulge region. One hair was elongated from the hair bulbs and the other was shed off from the fragments, suggesting that the latter was produced in the former hair cycle. Initiation of the second hair formation tended to be delayed when grafted fragments had been prepared from VFs in early anagen.

Conclusions: Whole VFs will keep their ability to advance hair cycles even if they are grafted and separated from the skin. TA cells in lower VFs can make a hair cycle proceed. These results support a hypothesis that TA cells in VFs are able to supply the matrix cells needed for not only a given hair cycle but also the subsequent ones, and subpopulations of TA cells with various sensitivities to apoptotic signals were differentially distributed in lower VFs, depending on hair cycles.