| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1998: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1997: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1996: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
In the present study we established a new in vivo model in which hair follicles individually isolated from human scalp skin were grafted onto back skin of severe combined immunodeficient mice, and investigated histological changes and cell kinetics in the degeneration and regeneration process of the hair follicles. These follicles showed the degeneration process from day 7 to 30, regeneration process from day 40 to 60, and the stable growth from day 70 to at least 150. Presence of significant melanin incontinence and preservation of hair bulb with dermal papilla throughout the experimental period as well as the early regrowth of the hair without passing telogen phase indicate that hair loss of the grafted follicles was not due to telogen effluvium but due to anagen effluvium. In the degeneration phase, BrdU-labeled cells were remarkable reduced in the bulb, and K19- positive cells appeared there. In the regeneration phase K19-positive cells were replaced with BrdU-labeled cells. and th
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en, the inner root sheath (IRS) and hair shaft were formed. Even in this period apoptosis continued, In the stable growth phase, the grafted follicles are immunohistochemically and light microscopically similar to the normal hair follicle, These findings indicate that cell kinetics in anagen effluvium and its recovery is different from that in the normal hair cycle : Stem cells or their progeny that migrated to the bottom of the follicles from bulge early in the degenerative phaseor that had already resided there and survived could locate near dermal papilla and wait ready for proliferation in the reconstruction stage. They were converted to transiently amplifying cells by stimulation from dermal papilla in the regeneration phase.
Next, we used this model to identify the localization of follicular stem cells. Each mouse had been incorporated with 3H-thymidine (20muci/days for 14 days), and then labeled cells were detected with autoradiography 0, 28 and 56 days after completion of labeling. Immediately after labeling period the basal layer of the outer root sheath (ORS) at the hair bulb was not labeled with ^3H-thymidine, whereas epithelial cells of the other components of hair follicle, including the ORS, the IRS and hair matrix were all labeled. At day 28 labeled cells (label-retaining cell : LRC) were localized on the suprabasal layers of the ORS at thebulge and the basal layer of the ORS adjacent to lower end of the bulge. At day 56 the number of LRCs in the former portion was decreased, and those in the latter was disappeared. Instead, LRCs were also observed on the basal layer of the ORS near hair bulb. These data indicate that the most slowly cycling cells in hair follicle are localized on the basal layer of the ORS at bulge, and that the second most slowly cycling cells are localized on the suprabasal layers of the ORS at the bulge, and migrate to the hair bulb. Less
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